GEOCHRONOLOGY AND GEOCHEMISTRY OF MID-MIOCENE BONANZA LOW-SULFIDATION EPITHERMAL ORES OF THE NORTHERN GREAT BASIN, USA Except where reference is made to the work of others, the work described in this thesis is my own or was done in collaboration with my advisory commite. This thesis does not include proprietary or clasified information. _________________________ Derick Le Unger Certificate of Approval: _________________________ _________________________ James Saunders, Co-Chair Wilis Hames, Co-Chair Profesor Profesor Geology and Geography Geology and Geography _________________________ _________________________ Robert Cook Joe F. Pitman Profesor Emeritus Interim Dean Geology and Geography Graduate School GEOCHRONOLOGY AND GEOCHEMISTRY OF MID-MIOCENE BONANZA LOW-SULFIDATION EPITHERMAL ORES OF THE NORTHERN GREAT BASIN, USA Derick Le Unger A Thesis Submited to the Graduate Faculty of Auburn University in Partial Fulfilment of the Requirements for the Degre of Master of Science Auburn, Alabama May 10, 2008 iii GEOCHRONOLOGY AND GEOCHEMISTRY OF MID-MIOCENE BONANZA LOW-SULFIDATION EPITHERMAL ORES OF THE NORTHERN GREAT BASIN, USA Derick Le Unger Permision is granted to Auburn University to make copies of this thesis at its discretion, upon request of individuals of institutions at their expense. The author reserves al publication rights. ________________________ Signature of Author ________________________ Date of Graduation iv VITA Derick Unger, the son of David and Sheri Unger, was born July 23, 1982 in Sullivan, Indiana. He graduated from Sullivan High School in 2000 and continued on to Indiana State University were he received his Bachelor?s of Science degre in spring 2005. He entered the Graduate School at Auburn University in fal 2005. In the summer of 2007 he began working as an exploration geologist for Victoria Resources Corporation in northern Nevada. v THESIS ABSTRACT GEOCHRONOLOGY AND GEOCHEMISTRY OF MID-MIOCENE BONANZA LOW-SULFIDATION EPITHERMAL ORES OF THE NORTHERN GREAT BASIN, USA Derick Le Unger Master of Science, May 10, 2008 (B.S. Indiana State University, 2005) 152 Typed pages Directed by James Saunders and Wilis Hames Ore petrography, geochemistry, and geochronology data collected for some low- sulfidation epithermal precious metal deposits in the northern Great Basin indicate that the mid-Miocene deposits have consistent ore mineralogy, geochemistry that varies betwen two end members, and a narow range of ages. These deposits are coeval with bimodal volcanism and often clasified as ?volcanic-hosted.? However, a number of deposits in this study are not hosted by volcanic rocks and it appears that the host rock may significantly afect gangue mineralogy. New high precision 40 Ar/ 39 Ar geochronology vi conducted on previously undated deposits (or deposits with older, les precise K/Ar dates only), indicates that low-sulfidation epithermal Au-Ag mineralization in the northern Great Basin began around 16.5 Ma and continued until at least 15.6 Ma. This time frame adds further support to the hypothesis that these deposits are geneticaly related to the emergence of the Yelowstone hotspot near the present day intersection of the Idaho, Nevada and Oregon boarders. High-grade bonanza ores in these deposits consist of precious metal minerals inter-grown with quartz and adularia (KAlSi 3 O 8 ). The intimate asociation of precious metals with adularia, an ideal mineral for use in 40 Ar/ 39 Ar geochronology, alows for unambiguous dating of the precious metal mineralization event. For this study, five adularia crystals from each sample location were analyzed individualy rather than as a bulk sample. The efects of argon loss or gain are much more evident in single crystal analysis and thus can be mitigated during the final age calculation. Deposits in or near the Slumbering Hils (Jumbo, New Alma, Sandman and Ten Mile) northwest of Winnemucca, Nevada as wel as two locations on War Eagle Mountain, Silver City District, Idaho, were selected for geochronologic study. A new younger age of 16.53 ? 0.04 Ma at the 1? confidence level was determined for the Jumbo deposit. Evidence for exces Ar was found in the samples from Jumbo, which likely explains an anomalously old date of 17.3 Ma that was previously determined using K/Ar methods. The youngest deposit in the Slumbering Hils area is the New Alma deposit (16.03 ? 0.07 Ma), which sits just south of the Jumbo deposit. The Ten Mile and Sandman deposits fal in betwen with ages of 16.52 ? 0.04 Ma and 16.17 ? 0.04 Ma respectively. The presence of the recently mined Sleper deposit and the Sandman vii deposit, which is a curent exploration target, indicates the Slumbering Hils area may host other significant bonanza ores. War Eagle Mountain vein samples yielded ages of 16.31 ? 0.04 Ma and 15.61 ? 0.10 Ma. The geochronology data as a whole indicate that precious metal mineralization occurred in the region for a period of at least 1 Ma. Suites of ore samples from several low-sulfidation deposits in the northern Great Basin were collected to examine similarities and contrasts in the mineralogy and geochemistry. Polished thin section petrography and geochemical data indicate that the most common precious metal minerals are electrum and Ag-selenides, Ag-sulfides, and Ag-sulfosalts. A new clasification scheme, the ?epithermal trilinear diagram,? based on metal and metaloid contents in these ores, was devised to examine geochemical properties within and amongst deposits. Each geochemical sample plots as a point on a trilinear diagram based on certain metal (Au, Ag, Pb) and metaloid (As, Sb, Te, Se) molar ratios. For the sake of comparison, some low-sulfidation ores from Colorado and Japan were included in this portion of the study. This new clasification scheme indicates deposits fal betwen two end members being either Ag-Se or Au-Te rich. The Colorado ores analyzed al fal in or near the Au-Te field, whereas samples from the northern Great Basin and Japan generaly plot in or near the Ag-Se field. The greatest determining factor in where a sample fals in this technique is the metaloid content. The high-grade nature of low-sulfidation epithermal precious metal deposits makes them atractive for mining. However, their relatively smal deposit footprint and susceptibility to erosion makes them dificult exploration targets. A beter genetic and exploration model can be developed by understanding factors such as the limited age vii range for formation, the broader range of host rocks than generaly recognized, and the typical geochemical signature of these deposits. ix ACKNOWLEDGEMENTS This research was supported by a grant form the United States Geological Survey (#05HQGR0153) to Saunders and Hames, and a student research grant from the Society of Economic Geologists. I would like to thank al the members of my commite for endles help, guidance and interesting stories. I would also like to think Bil Uterback, James Saunders, and Robert Cook for providing some samples. Thank you to Newmont Gold Corporation and Hecla Mining Company along with Great Basin Gold for aces to the Ken Snider and Hollister mines, respectively. x Style manual or journal used: Economic Geology Computer software used: Microsoft Word, Microsoft Excel, Microsoft Powerpoint, Isoplot, Minitab, Adobe Ilustrator, Adobe Photoshop xi TABLE OF CONTENTS LIST OF FIGURES......................................................................................................vii LIST OF TABLES......................................................................................................xvii INTRODUCTION...........................................................................................................1 PREVIOUS WORK........................................................................................................3 Low-sulfidation Precious Metal Systems..............................................................3 Precious Metal Source.........................................................................................5 Regional Geology................................................................................................7 Geology of Mining Districts.................................................................................8 Slumbering Hils......................................................................................8 Northern Carlin Trend............................................................................10 Silver City, Idaho...................................................................................12 National.................................................................................................13 Geochronology of Low-sulfidation Epithermal Deposits....................................15 METHODOLOGY........................................................................................................18 Field Methods....................................................................................................18 Ore Petrography.................................................................................................18 Geochemistry.....................................................................................................19 Geochronology..................................................................................................21 ORE PETROGRAPHY.................................................................................................23 xii GEOCHEMISTRY........................................................................................................38 Statistical Analysis.............................................................................................43 Epithermal Trilinear Diagram............................................................................47 Geochemical District Descriptions.....................................................................49 National.................................................................................................49 War Eagle Mountain..............................................................................50 Northern Carlin Trend............................................................................51 Slumbering Hils....................................................................................53 Japanese Epithermal Deposits.................................................................55 Colorado Teluride Deposits...................................................................57 GEOCHRONOLOGY...................................................................................................59 Geochronology Technique and Results..............................................................59 Slumbering Hils Deposits.................................................................................62 Sandman................................................................................................63 New Alma..............................................................................................66 Jumbo....................................................................................................68 Ten Mile................................................................................................70 War Eagle Mountain Deposit.............................................................................72 DISCUSION...............................................................................................................76 Ore Petrography.................................................................................................76 Geochemistry.....................................................................................................77 Geochronology..................................................................................................79 CONCLUSIONS...........................................................................................................82 xii SPECULATIONS AND IMPLICATIONS FOR EXPLORATION................................86 REFERENCES..............................................................................................................89 APENDIX 1 ...............................................................................................................99 APENDIX 2 .............................................................................................................101 APENDIX 3 .............................................................................................................131 xiv LIST OF FIGURES FIG. 1. Diagramatic ilustration of the ?porphyry-epithermal? transition and possible asoicated deposit types, modified form Hedenquist and Lowenstern, (1994).........................................................................................................6 FIG 2: Shaded relief map of the northwestern United States depicting selected Cenozoic tectonomagmatic features. Gren shading depicts the region where mid- Miocene Columbia River (WA-OR-ID) and Stens (OR-NV-ID-CA) flood basalt lava flows crop out (after Hart and Carlson, 1985; Camp and Ross, 2004; Brueseke et al., 2007). The major flood basalt dike swarms/eruptive loci are depicted as red lines, the Oregon-Idaho graben (OIG) and magnetic anomalies corresponding to zones of lithospheric extension/mafic magma emplacement (NR; northern Nevada rift) are depicted as black dashed lines (Cummings et al., 2000; Glen and Ponce, 2002). The Owyhee Mountains are labeled (OM) and denoted by an arow. The purple ovals are the silicic-dominated volcanic systems of the Snake River Plain- Yelowstone province; BJ, Bruneau-Jarbidge (~12.5 to <11 Ma); TF, Twin Fals (~10 to 8.6 Ma); PC, Picabo (~10 Ma); HS, Heise (~6.7 to 4.3 a); and YS, Yelowstone (<2.5 Ma), and the purple lines are the age isochrons asociated with Oregon High Lava Plains silicic activity (N, Newbery Volcano; after Jordan et al., 2004). The initial 87 Sr/ 86 Sr 0.706 and 0.704 isopleths are depicted (after Armstrong et al., 1977; Kistler and Peterman, 1978; Leman et al., 1992; Craford and Grauch, 2002) and are interpreted to define the western edge of the Precambrian North American craton (the 0.706 isopleth), and a zone of transitional lithosphere betwen the older craton and Mesozoic acreted teranes to the west (betwen the two isopleths). The blue shaded region depicts the portion of the Oregon Plateau (OP) characterized by mid-Miocene silicic magmatism..........................................................16 FIG. 3. Photograph and photomicrograph of ore-bearing adularia used for 40 Ar/ 39 Ar geochronology. A. Binocular microscope view of adularia grains with visible electrum. B. Photomicrograph (cross-polarized light) of euhedral adularia crystals with characteristic feather-like extinction (Photomicrograph scale bar = 1 m).............19 FIG. 4. Photograph of crustiform adularia crystals from the Sandman deposit, forming a thin layer (3-4 m) over the silicified tufaceous host rock............................24 FIG. 5 Sample HCN-1, Sandman deposit. Photograph of gold bearing adularia vein and breciated tuffaceous host rock. Note the surface layer of alteration to white clay..............................................................................................................................25 xv FIG. 6. Sample NMD-2, National deposit. A. Photograph of dendritic electrum. B. Photomicrograph (reflected light) of electrum (elt) and pyrargyrite (par). C. Photomicrograph (crossed polars) of jig saw quartz surrounding electrum and pyrargyrite. (Photomicrograph scale bar = 1 m). Note: photo inserts indicate the area the photomicrograph was taken, not necesarily the field of view...........................27 FIG. 7. Sample: BNM, Buckskin National deposit. A. Photograph of banded quartz vein with sagenitic naumannite. B. Photomicrograph (reflected light) of sagenitic naumannite. C. Photomicrograph (crossed polars) of jig saw quartz surrounding sagenitic naumannite. (Photomicrograph scale bar = 1 m)...........................................28 FIG. 8. Sample HSC-1, Hollister deposit. A. Photograph of banded ore with a central quartz vein (qtz) surrounded by two clay-rich veins (clay/qtz), clay-rich veins contain quartz replacement of bladed calcite, also note the sluice box textures of the naumannite and electrum in these layers as the ore minerals are deposited primarily on the leward (left) side. B. Photomicrograph (crossed polars) of quartz surrounding ore minerals. C.Photomicrograph (reflected light) of electrum (elt) rimed by pyrite (pyr) and naumannite (nam). D. Photomicrograph (reflected light) of pyrite (pyr) replaced by naumannite (nam) and pyargyrite (par). (Photomicrograph scale bar = 0.1 m)..........................................................................29 FIG. 9. Sample: WEMBU, Oro Fino vein, War Eagle Mountain. Photomicrograph (reflected light) of galena (gal) rimed by naumannite (nam) and chalcopyrite (cpy). (Photomicrograph scale bar = 0.1mm)................................................................30 FIG. 10. Sample BNM-2, Buckskin National deposit. Photograph of banded ores with typical cyclic deposition of quartz (qtz), electrum (elt), and Ag- selenides/sulfides (Ag-Se/S) in discret bands...............................................................31 FIG. 11. Sample OF-1, War Eagle Mountain deposit. A. Photograph of Oro Fino vein. Sequence of events appears to be altered basalt brecia covered by a band of quartz (qtz) then a band of Au/Ag-bearing adularia (adl). B. Photomicrograph (reflected light) of the quartz/adularia boundary with naumannite (nam) bearing adularia. C. Photomicrograph (crossed polars) of the quartz/adularia boundary, note the microcrystaline quartz (mqtz) band at the boundary and the much coarser naumannite-bearing adularia. (Photomicrograph scale bar = 1 m)...............................33 FIG. 12. Sample MGCV-2 banded ores from the Midas deposit. A. Photograph of banded vein showing at least six deposition events. B. Photomicrograph (plane polarized light) of the banded vein. C. Photomicrograph (reflected light) of electrum (elt) and naumannite (nam) in the jig saw quartz portion of the vein. D. Photomicrograph (crossed polars) of the banded vein, note the euhedral quartz (qtz) band bounded on both sides by ore bearing calcite/jig saw quartz (qtz/c) bands. (Photomicrograph scale bar = 1 m).............................................................................34 xvi FIG. 13. Sample MGCV-1, Midas deposit. A. Photograph of banded ore with two stages of bladed calcite (c) and bands of quartz (qtz), adularia, and naumannite (nam) in betwen. B. Photomicrograph (plane polarized light) of bladed calcite surrounded by quartz. C. Photomicrograph (crossed polars) of bladed calcite surrounded by quartz. (Photomicrograph scale bar = 0.5 m)........................................35 FIG. 14. Sample HGV-3, Hollister deposit. A. Photograph of quartz pseudomorphs after calcite in banded ore with abundant Ag-minerals (Ag) and base metal sulfides (bms) along the margins of calcite replacement. B. Photomicrograph (crossed polars) of microcrystaline quartz, which has replaced the bladed calcite. (Photomicrograph scale bar = 1 m).............................................................................36 FIG. 15. Sample HSC-2, Hollister deposit. A. Photograph of bladed quartz after calcite below a band of ore-bearing quartz. B. Photomicrograph (plane polarized light) of quartz pseudomorphic after calcite. C. Photomicrograph (crossed polars) of quartz pseudomorphic after calcite. Note that the quartz grains are much coarser relative to those in Fig. 12. (Photomicrograph scale bar = 1 m)...................................37 FIG. 16. Map Showing locations for many of the 17-14 Ma low-sulfidation epithermal deposits in the northern Great Basin (modified from Saunders et al. 1996), through-going structures as defined by geophysical data (Ponce and Glen, 2002) and the regional trend (dashed contours) of Cenozoic-subduction magmatism (McKe and Moring, 1996). Deposits sampled for this study are colored in red.............39 FIG. 17. Ilustration of proposed fields for the modified trilinear diagram. Au- telurides (yelow) and Ag-selenides (red). Chondritic meteorite data (Anders and Grevese, 1989) are also plotted here (blue square) and are though to miic mantle chemistry (Winters, 2001), or at least early earth mantle................................................49 FIG. 18. Epithermal trilinear diagram of several northern Great Basin deposits showing the broad spectrum of ore chemistries. Hog Ranch (Bussey, 1996) and Mule Canyon (John et al., 2003) data are plotted for comparison. Note some of the Buckskin National data points are obscured by the overlapping War Eagle Mountain points............................................................................................................51 FIG. 19. Epithermal trilinear diagram of the Hollister and Midas deposits both of which plot within the Ag-selenide field.........................................................................52 FIG. 20. Epithermal trilinear diagram of Slumbering Hils area deposits shows a gradual change in deposit geochemistry from north to south..........................................55 FIG. 21. Epithermal trilinear diagram of Koryu and Hishikari, Japan (Izawa et al. 1990).............................................................................................................................57 xvii FIG. 22. Epithermal trilinear diagram of Colorado Au-teluride deposits which defines the teluride field...............................................................................................58 FIG. 23. Map of Slumbering Hils area deposits. Modified from Wendt (2003)............63 FIG. 24. Release spectrum and plateau ages for five single adularia crystals (14-20 mesh size, 1.2-0.75 m) of sample HCN-1 from the Sandman deposit. Steps used to define the plateau are shaded. Erors for individual steps and plateau ages are at 1?. Se Appendix 2 for incremental heating data. Iradiation filenames are as follows: A) au5.1a.adl.ih1, B) au5.1a.adl.ih2, C) au5.1a.adl.ih3, D) au5.1a.adl.ih4, and E) au5.1a.adl.ih1.....................................................................................................65 FIG. 25. Release spectrum and plateau ages for five single adularia crystals (14-20 mesh size, 1.2-0.75 m) of sample HCN-2 from the New Alma deposit. Steps used to define the plateau are shaded. Erors for individual steps and plateau ages are at 1?. Se Appendix 2 for incremental heating data. Iradiation filenames are as follows: A) au5.1c.adl.ih1, B) au5.1c.adl.ih2, C) au5.1c.adl.ih3, D) au5.1c.adl.ih4, and E) au5.1c.adl.ih1.....................................................................................................67 FIG. 26. Release spectrum and plateau ages for five single adularia crystals (14-20 mesh size, 1.2-0.75 m) of sample HCN-3RE from the Jumbo deposit. Steps used to define the plateau are shaded. Erors for individual steps and plateau ages are at 1?. Se Appendix 2 for incremental heating data. Iradiation filenames are as follows: A) au5.1f.adl.ih1, B) au5.1f.adl.ih2, C) au5.1f.adl.ih3, D) au5.1f.adl.ih4, and E) au5.1f.adl.ih1. Note anomalously old ages in initial or final increments of the analysis (arows) consistent with release of extraneous ?exces? 40 Ar......................69 FIG. 27. Release spectrum and plateau ages for five single adularia crystals (14-20 mesh size, 1.2-0.75 m) of sample HCN-4 from the Ten Mile deposit. Steps used to define the plateau are shaded. Erors for individual steps and plateau ages are at 1?. Se Appendix 2 for incremental heating data. Iradiation filenames are as follows: A) au5.1h.adl.ih1, B) au5.1h.adl.ih2, C) au5.1h.adl.ih3, D) au5.1h.adl.ih4, and E) au5.1h.adl.ih1. Note anomalously old ages in initial or final increments of some analysis (arows) consistent with release of extraneous ?exces? 40 Ar...................71 FIG. 28. Map of sample locations of OF-1 and WEMS3-1 taken from historic workings on War Eagle Mountain. Contour lines are labeled in fet..............................72 FIG. 29. Release spectrum and plateau ages for five single adularia crystals (14-20 mesh size, 1.2-0.75 m) of sample OF-1 from the Oro Fino vein. Steps used to define the plateau are shaded. Erors for individual steps and plateau ages are at 1?. Se Appendix 2 for incremental heating data. Iradiation filenames are as folows: A) au8.adl.31, B) au8.adl.32, C) au8.adl.33, D) au8.adl.34, and E) au8.adl.35...............74 E xvii FIG. 30. Release spectrum and plateau ages for five single adularia crystals (14-20 mesh size, 1.2-0.75 m) of sample WEMS3-1 from War Eagle Moutain site 3. Steps used to define the plateau are shaded. Erors for individual steps and plateau ages are at 1?. Se Appendix 2 for incremental heating data. Iradiation filenames are as follows: A) au8.adl.41, B) au8.adl.42, C) au8.adl.43, D) au8.adl.44, and E) au8.adl.45. Note anomalously old ages in initial or final increments of analysis E (arows) consistent with release of extraneous ?exces? 40 Ar.........................................75 xix LIST OF TABLES Table 1. Geochronology of Mid-Miocene Au-Ag Deposits in the Northern Great Basin Preformed Prior to This Study.............................................................................15 Table 2. Selected Geochemical Data for Epithermal Precious Metal Ores......................40 Table 3. Correlation Matrix of Log Normalized Concentration Data..............................44 Table 4. Correlation Matrix of Concentration Data........................................................45 Table 5. Summary of Geochronology Results................................................................61 Table 6. Revised Geochronology of Mid-Miocene Au-Ag Deposits in the Northern Great Basin ...................................................................................................................62 1 INTRODUCTION The complex geologic history of the northern Great Basin has resulted in a wealth of mineral resources including huge endowments of Au and Ag. The mid-Miocene low- sulfidation epithermal precious metal deposits of the northern Great Basin are atractive for mining because they frequently contain bonanza grades and can have Au contents of several milion ounces (Simons et al., 2005). However, due to their smal size and susceptibility to erosion, this type of deposit remains a dificult exploration target. A beter understanding of the genesis of low-sulfidation epithermal precious metal deposits could lead to new and more efective methods of exploration. Worldwide, low-sulfidation epithermal precious metal deposits have been atributed to a variety of extensional tectonic setings (Silitoe and Hedenquist, 2003). During the mid-Miocene the northern Great Basin experienced extension and rifting- related bimodal volcanism that has been linked to the formation of the low-sulfidation epithermal precious metal deposits in the region (John, 2001). The first volcanism related to the Yelowstone hotspot also occurred in the region during this time (Brueseke et al., 2007). The genetic link betwen the mid-Miocene Au-Ag deposits and the initiation of the Yelowstone hotspot was first proposed by Saunders et al. (1996). A strong temporal and spatial relationship exists betwen the first volcanism of the Yelowstone hotspot and the mid-Miocene deposits (se below). However, a number of questions about the genesis 2 of these deposits remain including: what role (if any) the Yelowstone hotspot played in their formation and, from what source the Au, Ag, and other epithermal suite elements were derived? The lack of exploration activity in the northern Great Basin during the late 1990?s and early 2000?s has meant very few new deposits of this type have been discovered or researched. Thus, only a smal number of deposits have been evaluated using modern methods of geochronology and geochemistry. This study sought to provide new geochronology data for low-sulfidation epithermal precious metal deposits in the northern Great Basin that had either been significant historic producers or are the target of current exploration. Additionaly, a broader look at other northern Great Basin mid-Miocene low-sulfidation deposits was preformed, along with ores from deposits in Colorado and Japan for comparison, to contrast ore mineralogy and geochemistry. The possibility that these deposits could be related to a mantle plume has important exploration implications. Not only would other areas worldwide with past or present mantle plume activity represent prospective targets but, the areas further east of the northern Great Basin within the Yelowstone hotspot track may also represent areas of potential. 3 PREVIOUS WORK Low-sulfidation Epithermal Precious Metal Systems Epithermal systems form at shalow depths (<2 km) and low temperatures (< 300? C) and are clasified as high-sulfidation, intermediate-sulfidation, and low-sulfidation based on ore mineralogy, alteration, and gangue mineral asemblages (Hedenquist and Lowenstern, 1994; Simons et al., 2005). Low-sulfidation hydrothermal systems are generaly asociated with bimodal (basalt-rhyolite) or intermediate composition volcanism in a wide range of extensional tectonic setings (e.g., Silitoe and Hedenquist, 2003). The ore-forming fluids in low-sulfidation hydrothermal systems are low-salinity, near-neutral pH, sulfide-dominated, and reducing (Hedenquist and Lowenstern, 1994). Low-sulfidation deposits most often form distal from the magmatic heat source (Silitoe 1989). These deposits are shalowly emplaced and easily eroded, thus few deposits older than Tertiary age are known. A number of larger low-sulfidation epithermal Au-Ag deposits in the northern Great Basin have been the subject of one or more papers including: Midas (Goldstrand and Schmidt, 2000; Leavit et al., 2004), Hollister (Bartlet et al., 1991; Walace, 2003), Mule Canyon (John et al., 2003), Ten Mile (Bowel et al., 2000), Sleper (Saunders, 1990; Conrad et al., 1993; Saunders, 1994; Saunders and Schoenly, 1995; Nash et al., 1995), National and Buckskin-National (Vikre, 1985; Vikre 1987; Vikre 2007). 4 Epithermal precious metal deposits have also been examined in a regional context by John (2001) and John et al. (1999). These studies have established a number of general characteristics of low-sulfidation epithermal precious metal deposits in the region, including their relationship to extensional tectonism and bimodal volcanism. The ore textures for low-sulfidation epithermal precious metal deposits in the northern Great Basin and abroad have been wel documented by a number of deposit- specific and overview studies (se above). Colloform banded-veins, atributed to multiple pulses of mineralizing fluids, have been reported at many wel-known deposits. Alternating layers of quartz, chalcedony, adularia, calcite, clay, electrum, Ag-selenides, Ag-sulfides, Ag-sulfosalts, and/or base metal sulfides have been noted at: National and Buckskin National (Vikre, 1985; Vikre, 2007), Hishikari (Izawa et al., 1990), Sleper (Saunders, 1994; Saunders et al., 1996), Hog Ranch (Bussey, 1996), Midas (Goldstrand and Schmidt, 2000), and Mule Canyon (John et al., 2003). Adularia has long been recognized as a common gangue mineral in these deposits and was first reported in the region by Lindgren (1898) in the Black Jack-Trade Dollar vein on Florida Mountain in the Silver City district, Idaho. Adularia encrustations on open fractures are a common texture at the Jumbo, New Alma, Sandman and Ten Mile deposits in this study, and similar textures have been reported at Martha Hil, New Zealand (Simons et al., 2005). Electrum dendrite textures were reported and shown to vary acording to depth and temperature at the Jumbo, Midas, National, Seven Troughs, Sleper, and Ten Mile deposits by Saunders et al. (1996). This texture indicates that Au and Ag were transported as colloids and deposited rapidly from supersaturated fluids (Saunders 1994; Saunders et al., 1996). Bladed calcite and its psuedomorphic replacement by quartz are considered 5 indicators of boiling in an epithermal system (Simons and Christensen, 1994). Such textures have been observed at National and Buckskin National (Vikre, 1985), Sleper (Saunders, 1994), Midas (Goldstrand and Schmidt, 2000), Mule Canyon (John et al., 2003), and Martha Hil, New Zealand (Simons et al., 2005). Additionaly, at Midas, Goldstrand and Schmidt (2000) reported the deposition of Au/Ag-minerals on the leward side of quartz, suggesting they were transported as colloids. That study also found Au/Ag-mineral deposition at or near quartz-adularia boundaries, similar textures are present in some samples collected for this study. Precious Metal Source The ultimate source of the precious metals in low-sulfidation epithermal systems is an isue that has been debated for over one hundred years. The two most common theories propose metals are either leached from local host rocks or derived from magmas. A previous study by John (2001), of mid-Miocene low-sulfidation epithermal deposits in the northern Great Basin, determined these deposits are related to a bimodal volcanic asemblage of mid-Miocene age. However, John (2001) states that the precise role that magmas had in the formation of these deposits ?remains ambiguous.? As recently as the 1990?s some deposit models suggested that metals were sourced from leaching of local host rocks (e.g., Sleper, Nash et al., 1995). The Hedenquist and Lowenstern (1994) model links epithermal precious metal deposits to porphyry systems; and indicates magmatic fluids are important contributors to epithermal hydrothermal systems (Fig. 1). 6 FIG. 1. Diagramatic ilustration of the ?porphyry-epithermal? transition and posible asociated deposit types, modified form Hedenquist and Lowenstern (194). Later work has shown that magmatic fluids can transport Au from the porphyry environment into shalower epithermal systems (Heinrich et al., 2004; Heinrich, 2005). Dep hydrothermal waters at an actively-forming low-sulfidation Au deposit at Lihir Volcano, contain extremely high levels of disolved Au as bisulfide complexes (Simons and Brown, 2006), which suggests that epithermal Au deposits could form in time spans of tens of thousands of years, or les (Heinrich, 2006). Lead-isotope data from the same deposit (Ladolam, Lihir Island) also indicates that ore metals were derived from a single volatile-rich magma pulse, rather than hydrothermal leaching of the local volcanic host rocks (Kamenov et al., 2005). It has also been suggested that basaltic rather than rhyolitic magmas maybe responsible for Au-bearing fluids. There are some geochemical and isotopic data to support this theory (Noble et al., 1988; Connors et al., 1993; Kamenov et 7 al., in pres), as wel as petrography from another study that found native gold and copper blebs present in olivine phenocryst in a picrite lava (basalt) (Zhang et al., 2006). Regional Geology The complex geologic history of the northern Great Basin has resulted in numerous mineralizing events and deposit types. During the Nevadan, Elko, Sevier, and Laramide orogenies (Mesozoic to early Cenozoic), east-dipping subduction beneath western North America resulted in acretion of island arc teranes to the west in California, Cordilera-wide contraction from west to east, and widespread calc-alkaline magmatism throughout the northern Great Basin (John, 2001). A transition to extension occurred in the late Eocene, possibly due to the removal of the subducted Faralon plate from the North American lithosphere (Cline et al., 2005). Concurrent initiation of high-K calc-alkaline magmatism and formation of most Carlin-type Au deposits occurred betwen 42 and 36 Ma (Cline et al., 2005). Although strong temporal and spatial relationships exist, the role of magmatism in the formation of Carlin-type deposits is stil debated (se discussion in Muntean et al., 2004). Beginning about 17 Ma, extension became more widespread and along with coincident bimodal volcanism created the Basin and Range physiography of the region today (John, 2001). The earliest stages of bimodal volcanism, including that asociated with the northern Nevada rift, have been atributed to either back-arc extension and/or the impingement of the Yelowstone hot spot with the upper crust (Brueseke et al., 2007). Early workers noted the asociation of basalt dike swarms with a single prominent magnetic anomaly, which represents the northern Nevada rift (Zoback and Thompson, 8 1978; Zoback et al., 1994). Further work by Ponce and Glen (2002) identified thre additional linear aeromagnetic highs, which they interpret to be subparalel rifts similar in composition and genesis to the northern Nevada rift. Al of these rifts are spatialy asociated with mid-Miocene bimodal volcanic centers. A strong spatial link betwen the rifts and mid-Miocene epithermal Au-Ag deposits exists (Ponce and Glen, 2002) and rift related igneous activity is reported to have occurred predominately betwen 16.5 and 15 Ma (John et al., 2000). It has also been suggested that the development of the northern Nevada rift and a number of other large-scale fractures in northern Nevada is related to the Yelowstone hotspot (Zoback and Thompson 1978; Zoback et al., 1994; Pierce et al., 2000; Glen and Ponce, 2002). However, there is no consensus on where the Yelowstone hotspot originated, and by what mechanism it formed the large-scale fractures. Recent detailed studies of the Santa Rosa-Calico Range, the host of the National district, suggest that volcanism (at least in that study area) contains numerous intermediate compositions and therefore is not strictly bimodal as previously thought (Brueseke and Hart, 2004). Basaltic volcanism in the Santa Rosa-Calico range and at Stens Moutain occurred from about 16.73 ? 0.04 to 14.35 ? 0.38 Ma and 16.58 ? 0.18 to 15.51 ? 0.28 Ma respectively (Brueseke et al., 2007). These ages are some of the earliest for mid-Miocene bimodal volcanism in the Great Basin and may reflect the initiation of the Yelowstone hotspot in the region. Geology of Mining Districts Slumbering Hils: The Slumbering Hils and surrounding pediment contain a number of low-sulfidation Au-Ag deposits that have been significant recent or historic 9 producers including the Jumbo, New Alma, Sleper, and Ten Mile deposits as wel as the Sandman deposit, which is currently being evaluated for resource potential. The Slumbering Hils consist primarily of Mesozoic slates and phyllites of the Auld Lang Syne Group as wel as a Cretaceous granitoid stock (Wilden, 1964). Unconformably overlying these are Tertiary volcanics including ash-flow tufs that corelate with tuffs of the McDermit volcanic field to the north (Rytuba and McKe, 1984; Rytuba, 1989). The Awakening district is located in the northern half of the Slumbering Hils and hosts a number of mineral deposits including the historicaly mined Jumbo and New Alma deposits as wel as the recently mined Sleper deposit. The gold-bearing quartz- adularia stockwork-veins at Jumbo and New Alma are primarily hosted in Mesozoic metamorphosed argilaceous rocks (Wilden 1964). Production at the Jumbo deposit up to 1963 approached $1,000,000 (Wilden, 1964). The Sleper deposit sits just northwest of Jumbo in the pediment and was originaly covered by 10 to 50 m of aluvium (Conrad et al., 1993). Production at the mine occurred from 1986 to 1996 with over 1.6 Moz. of Au recovered (Conrad and McKe, 1996; John, 2001). Tertiary volcanics in the Sleper mine area consist of a basil unit of volcaniclastic rocks followed by intermediate composition lava flows and lapili tuf (Conrad et al., 1993). These units are overlain by the major ore host at the Sleper deposit, rhyolite porphyry emplaced from 16.5 to 16.3 Ma just prior to eruption of peralkaline volcanics from the McDermit volcanic field to the north (Conrad and McKe, 1996). The main period of high-grade Au/Ag vein formation began around 16.1Ma and is though to have continued for about 700,000 yrs. (Conrad and McKe, 1996). The other volcanic rocks in the Slumbering Hils are significantly younger than the Sleper veins and rhyolite porphyry host rock; these units 10 do not appear to have a connection with any mineralization or alteration at the Sleper deposit (Conrad and McKe, 1996). To the south of the Slumbering Hils and 15 km northwest of Winnemucca, Nevada is the Ten Mile district. The Ten Mile district contains low-sulfidation adularia- sericite type deposits hosted in argilaceous-arenite rocks of the Triasic Raspbery Formation (Bowel et al., 2000). These deposits are unique in that unlike the other northern Great Basin deposits in this study, they share no known temporal or spatial relationship to Miocene rhyolites, and none are present within the district (Nash, 1972; Saunders et al., 1996). Production in the district is believed to have been about 20,000 oz. Au from 1900 through 1942 (Bowel et al., 2000). Just north of the Ten Mile district is the Sandman deposit previously dril by Newmont Gold and currently the subject of exploration activity by Fronter Development Group (acquired from New West Gold) (ww.frontergroup.com). Current measured and indicated resources at the property are 271,000 oz. Au (Fronter pres release, Nov. 6, 2007). Northern Carlin Trend: The Carlin Trend is an approximately 37 mile long north- northwest alignment of Eocene sediment-hosted gold deposits, located near the town of Carlin, Nevada (Teal and Jackson, 1997). Unlike the rest of the Carlin Trend, the northern Carlin Trend hosts the Midas and Ivanhoe mining districts, which contain Miocene low-sulfidation epithermal precious metal deposits. These deposits difer considerably from the Eocene age Carlin-type deposits, which tend to be large low-grade diseminated gold-silver deposits (Cline et al., 2005). The relationship betwen the Eocene and Miocene deposits is not clear. It has been suggested that the Midas district could represent the northern extension of the Carlin Trend and, that the deposits there 11 formed during Miocene reactivation of a regional dextral and normal slip fault zone (Goldstrand and Schmidt, 2000). The Midas and Ivanhoe districts also are located near the eastern margin of the Northern Nevada Rift, which shares a strong temporal and spatial relationship with many of the low-sulfidation epithermal precious metal deposits of the northern Great Basin (se above). The Midas district hosts numerous historic workings along with the currently active Ken Snyder mine. Host rocks in the Midas district consist of a bimodal suite of felsic ash-flow tuffs, flows, plugs, volcaniclastic sediments along with mafic sils and dikes (Goldstrand and Schmidt, 2000). Hydrothermal activity at Midas appears to have begun around 15.6 Ma at the earliest and continued until 15.2 Ma (Leavit et al., 2004). Volcanics asociated with mineralization in the Midas area include the red rhyolite and Sawtooth dike, which have ages of 15.6 and 15.4 Ma respectively (Leavit et al., 2004). Ages for high-grade veins in the district range from 15.4 to 15.3 Ma (Leavit et al., 2004). The Ivanhoe district sits approximately 15 km to the southeast of the Midas district. It contains very similar epithermal precious metal deposits along with related mercury deposits. Early mining activity focused on cinnabar-bearing hot spring-type sinter and silica replacement deposits hosted in volcanic and sedimentary rocks (Walace, 2003). Later exploration activities identified several diseminated gold resources beneath the mercury deposits, one of these being the Hollister deposit (Walace, 2003). During the early 1990s low-grade diseminated gold ores were mined from two open pits (Hollister et al., 1992; Tewalt, 1998). Later deep driling by Great Basin Gold Ltd. (ww.greatbasingold.com) identified a series of high-grade gold-silver veins, hosted in Ordovician sedimentary rocks, near the Hollister open pits (Price, 2001). The 12 diseminated ores have been dated at 15.1 ? 0.4 Ma with K-Ar (Barlet et al., 1991) and the nearby vein deposits are 15.16 ? 0.05 Ma (Peppard, 2002). This overlap in uncertainties along with oxygen isotope data suggests that both deposits, along with the overlying mercury sinter deposits, are related to the same hydrothermal system and, that the veins served as feders for the near-surface mercury and diseminated gold deposits (Peppard, 2002; Walace, 2003). Mercury-gold mineralization in the district occurred from about 15.2 to 14.9 Ma along with rhyolitic volcanism and high-angle faulting (Walace, 2003). Silver City, Idaho: The area surrounding Silver City in southwest Idaho contains the War Eagle Mountain and Florida Mountain deposits in the Silver City district and neighboring DeLamar deposit in the DeLamar district. Historic production first began in the Silver City area on War Eagle Mountain in the 1860?s, followed by production at DeLamar in 1890, and Florida Mountain in 1892 (Lindgren, 1900). Production at War Eagle Mountain had nearly ceased and many of the old workings were inacesible by the time Lindgren examined the area in 1897 (Lindgren, 1900). The Oro Fino vein system is credited as the most productive on War Eagle Mountain and produced $7 milion in gold and silver ore (Lindgren, 1900). Adularia (caled valencianite by Lindgren) is also noted as common gangue mineral in some of the veins at War Eagle Mountain, Florida Mountain and DeLamar (Lindgren, 1898; Lindgren 1900). Lindgren?s 1898 report is the first published acount of adularia in the northern Great Basin. More recently, the DeLamar silver mine to the west of Silver City produced 17 milion ounces of silver and 230 thousand ounces of gold from 1977 to 1987 (Halsor et al., 1988). The deposits in both the DeLamar and Silver City districts share a temporal 13 and spatial relationship with the western Owyhee volcanic field, which consists of middle Miocene basalts and younger middle Miocene rhyolites (Halsor et al., 1988). These volcanics are underlain by granite of quartz monzonite to granodiorite composition that appears to correlate with the Idaho batholith based on petrologic similarities and a radiometric age of 65 Ma (Asher, 1968; Pansze, 1975). The middle Miocene volcanics of the Owyhee volcanic field are mostly absent on War Eagle Mountain but are abundant to the west in the area surrounding the DeLamar mine (Halsor et al., 1988). Basalts up to 800 m thick form the basal unit and have been dated using whole rock K-Ar methods to be 16.6 ? 4.3 Ma (Asher, 1968; Pansze, 1975). Overlying the basalts are pre- and postmineralization rhyolites. Premineralization rhyolites consist of coalescing flows from multiple volcanic sources and include the Silver City rhyolite (Asher, 1968). Ages for this unit cluster around 16.0 Ma (Pansze 1975). Postminerlization units exposed in the area include the Swisher Mountain tuff (Ekren et al., 1981), which is believed to be around 14 Ma based on ages for a corelative rhyolite at Poison Crek (Neil, 1975). North to northwest trending high-angle faults host veins at DeLamar and War Eagle Mountain (Halsor et al., 1988). Movement of up to several hundred meters is predominately vertical and pre- and postdates the emplacement of the basalts and rhyolites (Pansze, 1975; Ekren et al., 1981; Thomason, 1983). These faults are thought to be related to Basin and Range extension and rifting in the Snake River Plain (Pansze, 1975). National: The National district is located in northern part of the Santa Rosa Mountains in north central Nevada, 20 miles southeast of McDermit. The district hosts the National and Buckskin National deposits. As a whole the district produced 200,000 14 oz. gold and 750,000 oz. silver from 1906 to 1941 (Vikre, 1985). The area was first described in detail by Lindgren (1915) when production in the district was near its peak. Lindgren (1915) noted that although a few smal ore shoots such as the ?Stal Brothers? stope contained spectacularly high gold grades, the deposits as a whole contained much larger amounts of silver. Production of Hg also occurred from Hg-bearing silica sinter near the top of Buckskin Mountain (Roberts, 1940). Since the 1970?s a number of companies have explored the area around Buckskin National for vein-type deposits similar to those mined in the past. The area is currently being explored by Romarco Minerals Inc. (ww.romarco.com). Host rocks in the National district consist of a 3,000 ft. thick section of mostly Miocene volcanics that unconformably overlie Mesozoic metasedimentary rocks (Vikre, 1985). The oldest lithology with hydrothermal alteration is the rhyolite of Buckskin Mountain, with a sanidine age of 16.57 ? 0.03 Ma (Vikre, 2007). This unit overlies basalt and basaltic-andesite flows (ca. 16.7 Ma) similar to those of Stens Mountain (Brueseke et al., 2007). Overlying and intruding the rhyolite of Buckskin Mountain is porphyritic rhyolite (16.31 ? 0.03 Ma) that is overlain by lithophysic rhyolite (16.11 ? 0.03 Ma) (Vikre, 2007). The sinter and banded veins at Buckskin Mountain have been dated at 16.06 ? 0.03 Ma (Vikre, 2007). At National the large porphyritic intrusion that forms Charleston Hil and serves as the primary host rock has a sanidine age of 16.01 ? 0.15 Ma (Vikre, 2007). Emplacement of the vein and sinter deposits at Buckskin Mountain is thought to have occurred over several hundred thousand years and the entire hydrothermal system was active for about 500,000 years (Vikre, 2007). 15 Geochronology of Low-Sulfidation Epithermal Deposits In the northern Great Basin a mid-Miocene (17-13 Ma) time frame for ages of mineralization and volcanism related to low-sulfidation epithermal Au-Ag deposits has been measured by a number of studies using K/Ar and Ar/Ar methods (Table 1). Table 1. Geochronology of Mid-Miocene Au-Ag Deposits in the Northern Great Basin Preformed Prior to this Study Saunders et al. (1996) proposed that these deposits are related to the initial development of the Yelowstone hotspot. Other studies suggest that the Yelowstone hotspot, and flood basalt magmatism similar in age and composition to the Columbia River flood basalts, originated in the Nevada-Oregon-Idaho tri-state region betwen 17.5 and 16.5 Ma (Fig. 2; Hooper, 1997). Deposit Age ? 1? (Ma) Dating Method Predominant Host Rocks Reference Jumbo 17.3?0.5 K/Ar metasediments Conrad et al., 1993 War Eagle Mtn. 16.6-15.2 K/Ar granite Halsor et al., 1988 Sleper 16.1?0.07 Ar/Ar rhyolite Conrad and McKe, 1996 Buckskin National 15.8-15.4?0.2 K/Ar rhyolite Vikre, 1985 Mule Canyon 15.6?0.04 Ar/Ar rhyolite John et al., 2003 DeLamar 15.7?0.5 K/Ar rhyolite Halsor et al., 1988 McDermit (Hg) 15.6?0.4 K/Ar rhyolite Noble et al., 1988 idas 15.4-15.3?0.08 Ar/Ar rhyolite Leavit et al., 2004 Hog Ranch 15.2-14.8?0.4 K/Ar rhyolite Bussey, 1996 Hollister 15.19?0.05 Ar/Ar rhyolite Peppard, 2002 Seven Troughs 13.82?0.02 Ar/Ar rhyolite Hudson et al., 2006 16 FIG 2: Shaded relief map of the northwestern United States depicting selected Cenozoic tectonomagmatic features. Gren shading depicts the region where mid-Miocene Columbia River (WA-OR-ID) and Stens (OR-NV-ID-CA) flod basalt lava flows crop out (after Hart and Carlson, 1985; Camp and Ros, 204; Brueseke et al., 207). The major flod basalt dike swarms/eruptive loci are depicted as red lines, the Oregon-Idaho graben (OIG) and magnetic anomalies coresponding to zones of lithospheric extension/mafic magma emplacement (NR; northern Nevada rift) are depicted as black dashed lines (Cumings et al., 200; Glen and Ponce, 202). The Owyhe Mountains are labeled (OM) and denoted by an arow. The purple ovals are the silicic-dominated volcanic systems of the Snake River Plain- Yelowstone province; BJ, Bruneau-Jarbidge (~12.5 to <1 Ma); TF, Twin Fals (~10 to 8.6 Ma); PC, Picabo (~10 Ma); HS, Heise (~6.7 to 4.3 Ma); and YS, Yelowstone (<2.5 Ma), and the purple lines are the age isochrons asociated with Oregon High Lava Plains silicic activity (N, Newbery Volcano; after Jordan et al., 204). The initial 87 Sr/ 86 Sr 0.706 and 0.704 isopleths are depicted (after Armstrong et al., 197; Kistler and Peterman, 1978; Leman et al., 192; Craford and Grauch, 202) and are interpreted to define the western edge of the Precambrian North American craton (the 0.706 isopleth), and a zone of transitional lithosphere betwen the older craton and Mesozoic acreted teranes to the west (betwen the two isopleths). The blue shaded region depicts the portion of the Owyhe Plateau (OP) characterized by mid- Miocene silicic magmatism. Whereas the greatest degre of Columbia River flood basalt magmatism occurred to the north in northeastern Oregon and southwestern Washington, flood basalts at Stens Mountain in southern Oregon were coeval with eruption of the earliest and most voluminous Columbia River basalts (Brueseke et al., 2007), and overlap with the age of large silicic calderas at McDermit (Fig. 2). Thus, the mid-Miocene bonanza deposits of 17 the northern Great Basin are not only closely asociated with magmatism and extension that formed the northern Nevada rift, but they also may be broadly asociated with the inception of Yelowstone hotspot magmatism, and perhaps flood basalt magmatism. Previous studies, including Conrad et al. (1993) and John (2001), have established the general timing and age relationships for a few bonanza ores of northern Nevada. However, the bulk-sample total fusion (K/Ar and Ar/Ar) techniques used in most of the published studies yield relatively broad age constraints, due to their inability to resolve problems posed by the presence of extraneous argon or partial degasing following initial trapping. Given the mounting evidence that these deposits form during rapid deposition events over periods of tens to hundreds of thousands of years (Sanematsu et al., 2006; Simons and Brown 2006; Heinrich, 2006), wel constrained dates for deposit formation are needed to fully understand what geologic proceses are involved. 18 METHODOLOGY Field Methods Field work was caried to out to collect samples suitable for this study in northern Nevada and southern Idaho during the summer of 2006. Samples of probable mid- Miocene deposits, including historic mines, prospects and outcropping mineralization, were collected. Samples of ore-bearing quartz and/or adularia veins along with host rocks were described in the field and locations were recorded using a GPS receiver. Emphasis was placed on obtaining samples with visible precious metal minerals and adularia. Field work was mainly conducted by a team of thre, the author, Wilis Hames, and James Saunders, of Auburn University. Considerable advice on sampling sites, additional samples with maps of collection localities, and some field asistance was provided by Bil Uterback, a local expert on epithermal gold deposits based in Winnemucca, Nevada. Robert Cook also provided some samples and advice on sampling locations for the National district. Ore Petrography Both standard and polished thin sections were prepared for determination of suitable material for 40 Ar/ 39 Ar dating and to examine ore mineralogy and textures (Fig. 3). 19 FIG. 3. Photograph and photomicrograph of ore-bearing adularia used for 40 Ar/ 39 Ar geochronology. A. Binocular microscope view of adularia grains with visible electrum. B. Photomicrograph (cros-polarized light) of euhedral adularia crystals with characteristic feather-like extinction (Photomicrograph scale bar = 1 m). Standard thin sections were prepared in Auburn University?s thin section lab and polished thin sections were prepared by Vancouver GeoTech Labs. Thin section of-cuts were stained for K-feldspar. Petrography was preformed using a transmited and reflected light microscope. Mineral identification was aided by the acompanying geochemical data for each sample. Geochemistry The majority of the geochemistry samples were obtained by field collection. A few samples (e.g., HCN 1-4) were collected and provided by Bil Uterback. For comparison, additional samples representing wel known low-sulfidation Au/Ag-deposits from northern Nevada (Sleper and National), Colorado (Besie G, Sunnyside, Creson, Vindicator, and Black Rose), and Japan (Koryu), were provided by James Saunders and Robert Cook. Al samples were analyzed by ACME Analytical Labs LTD. 1 m A B 20 Before samples were sent to ACME, each was sawed in half, with one split used for geochemical analysis. The other half was retained as reference or made into a polished thin section. Geochemical samples were prepared to contain a minimum of host rock, and idealy contain a high ratio of ore minerals to gangue vein material. Thus, precious metal concentrations were maximized and are not necesarily representative of mining grades. Once the samples were sent to ACME, a sample of up to 1 kg was crushed to 70% pasing at 10 mesh followed by a 250 g split being pulverized to 95% pasing at 150 mesh. A multi-element asay for 34 elements including: Mo, Cr, Ba, Hg, Cu, Pb, Zn, Ag, Ni, Co, Fe, As, Sb, Sr, Se, and Te, was preformed by hot aqua regia digestion of a 1 g sample split followed by ICP-ES and ICP-MS analysis. Analysis for Au was preformed by fire asay. A Pearson correlation plot was created using MINITAB and used to evaluate elemental relationships using both log normalized and ?raw? concentration data. Only data from the northern Great Basin deposits was input into the correlation matrix. Any data that was below detection limits was reduced to one half of the detection limit as is the standard practice. A modified trilinear plot was devised to serve as a visual way to compare the chemical atributes of each deposit. The modified trilinear plot, henceforth caled the epithermal trilinear diagram, was created by plotting the molar ratios of Au, Ag, and Pb/10 on a cation trilinear diagram, and plotting the molar ratios of Sb/10+As/10, Se and Te on the anion trilinear diagram. These points were then projected onto the quadrilateral field of the trilinear diagram as normal. The concentrations of Pb, Sb, and As were 21 divided by a factor of ten to compensate for the fact that they have higher average abundances relative to the other elements. Geochronology Al 40 Ar/ 39 Ar dating was preformed in the Auburn Nobel Isotope Mas Analysis Lab (ANIMAL) under the direction of Dr. Wilis Hames. The mineral adularia (KAlSi 3 O 8 ) was dated because it is rich in K, and a common gangue mineral that is often intimately asociated with the Au/Ag-minerals. Each sample was crushed and sieved to 14-20 and 20-60 mesh size fractions for hand picking. Hand picking of each sample was preformed to select individual crystals or cleavage fragments, fre from visible inclusions of other phases, and generaly fre from alteration. Al samples were washed in dilute HF prior to analysis to remove any oxide coatings. Neutron iradiation at the central core facility of the McMaster Nuclear Reactor in Hamilton, Ontario was used for the production of 39 Ar and followed standard procedures as described by Dalrymple et al. (1981). Crystals were placed in aluminum disks with the monitor FC-2 (for J-value determination, age = 28.02 Ma, Renne et al., 1998) along with reagent grade K 2 SO 4 and CaF 2 as flux monitors. Following iradiation, the best technique for Ar extraction was determined by heating single adularia crystals with a CO 2 laser by the following methods: 1) total fusion, 2) two-step release, and 3) incremental heating. Incremental heating produced the most precise results and proved to be the best way to deal with the high radiogenic yields and extraneous 40 Ar typical of these samples. Heating schedules of 10- 20 steps were used for 5 adularia crystals from each sample location. The first several heating steps were preformed at low laser power and served to remove extraneous 40 Ar 22 contained on surface defects or in fluid inclusions. The middle steps tended to release the majority of Ar contained in the crystal latice, while the final steps served to totaly fuse the crystal and insure al the Ar had been extracted. An Excel spreadsheet and the Excel add-on Isoplot (Ludwig, 2003) was used for data reduction and to create model-age spectrum and isotope correlation diagrams. Se appendices 1, 2, and 3 respectively for additional lab descriptions, incremental heating data for each sample, and monitor and air data. 23 ORE PETROGRAPHY Ore petrography was conducted to locate suitable material for geochronology, and to determine the mineralogical relationships within veins that exist in each deposit. Standard and polished thin sections were prepared from the Buckskin National, Hollister, Midas, National, Sandman, and War Eagle Mountain deposits. Characteristic and other interesting features/textures in hand samples were also described and photographed so that textures on both the microscopic and macroscopic scale could be compared. For this study, deposits that contain adularia as a common ore-host were of particular interest because these samples provide the most direct method for dating precious metal mineralization. In these deposits, electrum is the primary Au-mineral, and a number of Ag-selenides, Ag-sulfides, and Ag-sulfosalts including: naumannite (Ag 2 Se), aguilarite (Ag 4 SeS), acanthite (Ag 2 S), pyrargyrite (Ag 3 SbS 3 ), and proustite (Ag 3 AsS 3 ) are common. Two distinct occurrences of adularia are present in the deposits evaluated for this study. The Jumbo, New Alma, Ten Mile and Sandman deposits contain thin (1- 20 m) veins or fracture encrustations of adularia ? quartz, which host electrum and/or gold almost exclusively. This contrasts with the deposits found at Buckskin National, Hollister, Midas, National, and War Eagle Mountain, which consist of much thicker (up to 5 m) banded quartz ? adularia ? calcite veins that generaly contain more Ag- selenides, sulfides and sulfosalts, along with rare high-finenes gold. Adularia has been 24 reported at most of the deposits in this study; however crystals large enough for dating were not found in the samples collected at the Buckskin National, Hollister, Midas, or National deposits. Deposits with veins containing principaly adularia or veins in which adularia served as the primary precious metal host, have been important historic producers but have not been mined recently on a large scale. In these deposits, adularia veins are typicaly narow (1 - 20 m), often form encrustations on open fractures, and precious metal minerals typicaly are located near the host rock/vein margins (Fig. 4 and 5). FIG. 4. Photograph of crustiform adularia crystals from the Sandman deposit, forming a thin layer (3-4 m) over the silicified tufaceous host rock. Electrum 1 cm 25 FIG. 5 Sample HCN-1, Sandman deposit. Photograph of gold bearing adularia vein and breciated tufaceous host rock. Note the surface layer of alteration to white clay. Native gold and electrum are nearly the exclusive ore minerals present in the adularia veins. Geochemical data indicate relatively low levels of base metals, Se, and Te (discussed below). Some of the Jumbo and New Alma samples have thin bands of quartz that either precede or overgrew the adularia. Field observations indicate these quartz layers are nearly baren of precious metals and geochemical data for one such layer (NEWA2-1) support this conclusion. The banded quartz ? adularia ? calcite veins collected for this study have considerably diferent features compared to the adularia-dominated veins. Unlike the adularia veins that often do not exced a few centimeters in thicknes, the banded veins Electrum 1 cm Clay alteration 26 range from les than 1 m up to 5 m in width and can be lateraly extensive for nearly 2 km with remarkable uniformity in mineral composition (Vikre, 1985; Goldstrandt and Schmidt 2000). Evidence for colloidal silica and deposition of ore minerals from colloids are also common. Colloids serve an important role in epithermal systems by transporting components from deeper in the system to the shalow environment (Saunders, 1994). Evidence for deposition of silica and precious metals from colloids is present in ores from the National district and the Hollister deposit. Samples from the National deposit contain dendritic electrum ?forests? along with pyrargyrite surrounded by ?jig saw? quartz (Fig.6). Additionaly, samples from the Buckskin National deposit contain dendritic naumannite, also caled ?sagenitic? by Vikre (1985), and numerous thin bands of jig saw quartz (Fig. 7). ?Sluice box? textures in samples from Hollister (Fig. 8) indicate electrum and Ag-sulfide/selenide colloids were caught up and deposited on the leward side of veins as they moved upward with the hydrothermal fluids. Similar textures have also been reported at Midas (Goldstrand and Schmidt, 2000). Electrum dendrites indicate rapid precipitation from a supersaturated solution and jig saw quartz forms when amorphous (colloidal) silica (re)crystalizes to form quartz (Saunders, 1994). These textures indicate both the silica and precious metals were deposited as colloids in a rapid manner from a supersaturated fluid (Saunders, 1994; Saunders et al., 1996). 27 FIG. 6. Sample NMD-2, National deposit. A. Photograph of dendritic electrum. B. Photomicrograph (reflected light) of electrum (elt) and pyrargyrite (par). C. Photomicrograph (crosed polars) of jig saw quartz surounding electrum and pyrargyrite. (Photomicrograph scale bar = 1 m). Note: photo inserts indicate the area the photomicrograph was taken, not necesarily the field of view. A B elt par C 1 cm B&C 28 FIG. 7. Sample: BNM, Buckskin National deposit. A. Photograph of banded quartz vein with sagenitic naumanite. B. Photomicrograph (reflected light) of sagenitic naumanite. C. Photomicrograph (crosed polars) of jig saw quartz surounding sagenitic naumanite. (Photomicrograph scale bar = 1 m). A C B&C B 1 cm 29 FIG. 8. Sample HSC-1, Holister deposit. A. Photograph of banded vein with a central quartz band (qtz) surounded by two clay-rich bands (clay/qtz), clay-rich bands contain quartz replacement of bladed calcite, also note the sluice box textures of the naumanite and electrum in these layers as the ore minerals are deposited primarily on the leward (left) side. B. Photomicrograph (crosed polars) of quartz surounding ore minerals. C.Photomicrograph (reflected light) of electrum (elt) rimed by pyrite (pyr) and naumanite (nam). D. Photomicrograph (reflected light) of pyrite (pyr) replaced by naumanite (nam) and pyargyrite (par). (Photomicrograph scale bar = 0.1 m). A D C B B&C D qtz clay/qtz elt nam pyr nam pyr par 30 There is evidence from ore textures on the microscopic scale that mineral deposition took place in stages at some deposits. Ores from the Hollister deposit show electrum rimed by naumannite and pyrite in one band, and naumannite and pyrargyrite replacing pyrite in another (Fig. 8). Additionaly, a sample collected at War Eagle mountain contains galena rimed by naumannite and chalcopyrite (Fig. 9). Similar textures of early base metal sulfides followed by later precious metal minerals have been reported in the National district and Midas deposit (Vikre, 1985; Goldstrand and Schmidt 2000). FIG. 9. Sample: WEMBU, Oro Fino vein, War Eagle Mountain. Photomicrograph (reflected light) of galena (gal) rimed by naumanite (nam) and chalcopyrite (cpy). (Photomicrograph scale bar = 0.1m). nam gal cpy 31 Veins that contain multiple generations of banding indicate systems that were fairly long lived and received input of fluids with diferent chemistries. Sample BNM-2 from the Buckskin National deposit is ~3 cm long and contains at least eight bands of Ag-selenides/sulfides (some with visible electrum), along with multiple layers of quartz in betwen (Fig. 10). FIG. 10. Sample BNM-2, Buckskin National deposit. Photograph of banded ores with typical cyclic deposition of quartz (qtz), electrum (elt), and Ag-selenides/sulfides (Ag-Se/S) in discret bands. Some of these ores also contain evidence of breciation, either tectonic or hydrothermal, during vein formation. Sample OF-1 from the Oro Fino vein, War Eagle Mountain contains altered basalt brecia, which was later over-grown by a layer of quartz, then a layer of naumannite-bearing adularia (Fig. 11). At the microscopic scale, naumannite is hosted by the adularia as smal blebs and the quartz appears baren. A thin band of much finer-grained quartz occurs at the quartz/adularia margin. 1 cm qtz Ag-Se/S elt 32 Deposition of precious metals frequently occurred near transition boundaries of either quartz and adularia (Fig. 11) or euhedral quartz and microcrystaline quartz (Fig. 12). The banding in these veins likely indicates a change in equilibrium or fluid chemistry that resulted in Au/Ag-mineral precipitation. Boiling is also considered an important deposition mechanism in epithermal systems. Bladed calcite (Fig. 13) and bladed quartz pseudomorphs (Fig. 14; Fig. 15), which indicate boiling (Simons and Christenson, 1994), are present at or near some metal deposition margins. 33 FIG. 1. Sample OF-1, War Eagle Mountain deposit. A. Photograph of Oro Fino vein. Sequence of events apears to be altered basalt brecia covered by a band of quartz (qtz) then a band of Au/Ag-bearing adularia (adl). B. Photomicrograph (reflected light) of the quartz/adularia boundary with naumanite (nam) bearing adularia. C. Photomicrograph (crosed polars) of the quartz/adularia boundary, note the microcrystaline quartz (mqtz) band at the boundary and the much coarser naumanite-bearing adularia. (Photomicrograph scale bar = 1 m). 1cm Altered Basalt Brecia qtz adl B&C qtz adl mqtz nam A C B 34 FIG. 12. Sample MGCV-2 banded ores from the Midas deposit. A. Photograph of banded vein showing at least six deposition events. B. Photomicrograph (plane polarized light) of the banded vein. C. Photomicrograph (reflected light) of electrum (elt) and naumanite (nam) in the jig saw quartz portion of the vein. D. Photomicrograph (crosed polars) of the banded vein, note the euhedral quartz (qtz) band bounded on both sides by ore bearing calcite/jig saw quartz (qtz/c) bands. (Photomicrograph scale bar = 1 m). A D C B B-D elt nam qtz qtz/c qtz/c 35 FIG. 13. Sample MGCV-1, Midas deposit. A. Photograph of banded ore with two stages of bladed calcite (c) and bands of quartz (qtz), adularia, and naumanite (nam) in betwen. B. Photomicrograph (plane polarized light) of bladed calcite surounded by quartz. C. Photomicrograph (crosed polars) of bladed calcite surounded by quartz. (Photomicrograph scale bar = 0.5 m). A 1 cm B&C C B cc qtz cc cc nam qtz adl 36 A B B FIG. 14. Sample HGV-3, Holister deposit. A. Photograph of quartz pseudomorphs after calcite in banded ore with abundant Ag-minerals (Ag) and base metal sulfides (bms) along the margins of calcite replacement. B. Photomicrograph (crosed polars) of microcrystaline quartz, which has replaced the bladed calcite. (Photomicrograph scale bar = 1 m). B 1 cm Ag bms 37 FIG. 15. Sample HSC-2, Holister deposit. A. Photograph of bladed quartz after calcite below a band of ore-bearing quartz. B. Photomicrograph (plane polarized light) of quartz pseudomorphic after calcite. C. Photomicrograph (crosed polars) of quartz pseudomorphic after calcite. Note that the quartz grains are much coarser relative to those in Fig. 12. (Photomicrograph scale bar = 1 m). B C A B&C 38 GEOCHEMISTRY Typical elemental enrichments for low-sulfidation epithermal precious metal systems are wel established; yet the actual concentrations of these elements vary considerably from deposit to deposit. The deposits of the northern Great Basin contain economic amounts of Au and Ag ? Hg, along with significant concentrations of As, Sb, Se, Mo, Tl, and W, which can be important pathfinders useful for exploration (John, 2001). Base metal contents are often low (Saunders, 1990; John, 2001) and selenium has been observed as an important component of ore minerals in some deposits (Vikre, 1984; Halsor et al., 1988; Goldstrand and Schmidt, 2000). A similar geochemical signature exists for the Japanese deposit examined in this study (Izawa et al., 1990). The deposits of Colorado have a geochemical signature similar to those of Nevada and Japan with the exception that Te, rather than Se, is abundant and an important constituent in ore minerals (Simons et al., 2005). Multi-element geochemical analysis was preformed on a number of samples from deposits within the northern Great Basin (Fig. 16) as wel as other low-sulfidation epithermal deposits from Colorado and Japan for comparison. Selected elements deemed most relevant are listed in Table 2; a complete table of al the geochemical data can be found as an Excel file in the acompanying CD-ROM appendix. 39 FIG. 16. Map Showing locations for many of the 17-14 Ma low-sulfidation epithermal deposits in the northern Great Basin (modified from Saunders et al. 196), through-going structures as defined by geophysical data (Ponce and Glen, 202) and the regional trend (dashed contours) of Cenozoic-subduction magmatism (McKe and Moring, 196). Deposits sampled for this study are colored in red. 40 Table 2. Selected Geochemical Data for Epithermal Precious Metal Ores Sample # Location Sample Type Au Mo Cu Pb Zn Ag As Sb Cr Ba Hg Se Te NOFS2-1 War Eagle Mtn. Qtz Vein 28 1.4 8 1 <5 108 <5 1 5 6 <.05 6 <1 OF-1 ar Eagle Mtn. Qtz\Adl Vein 56 1.5 117 104 12 2469 6 8 12 16 <.05 229 2 OF-2 War Eagle Mtn. Qtz\Adl Vein 1 0.9 71 5 <5 19 10 1 5 10 <.05 <2 <1 WEMS3-1 ar Eagle Mtn. Qtz\Adl Vein 7 <.5 179 36 <5 459 12 13 4 7 <.05 39 1 EMS3-2 War Eagle Mtn. Qtz\Adl Vein 2 <.5 24 5 5 145 <5 2 3 5 <.05 15 <1 WEMBU War Eagle Mtn. Adl Vein 149 1.9 1553 2313 1324 5725 <5 1 2 6 <.05 1689 18 BNM Buckskin National Qtz Vein 32 1.5 12 38 26 697 265 63 9 5 1.2 168 <1 BNM-2 Buckskin National Qtz Vein 78 1.6 25 36 83 3354 71 174 14 12 13.8 651 <1 BNM-3 Buckskin National Qtz Vein 782 2.2 200 1801 838 3300 44 648 12 <5 18.3 4952 <1 NMD National Qtz Vein 2 0.5 78 157 24 1335 586 1469 6 5 1.4 55 3 NMD-2 National Qtz Vein 32940 5.8 2905 107 289 3834 924 8175 21 71 72.4 143 <1 NMD-3 National Qtz Vein 170 2.4 125 51 45 210 5258 174 9 64 0.6 11 <1 NMD-4 National Qtz Vein 2 1.0 2216 40354 22613 202 46996 368 10 7 0.2 401 1 HGV-1 Holister Qtz\Clay Vein 437 3.1 487 166 74 372 339 53 8 16 0.5 89 4 HGV-2 Holister Qtz\Clay Vein 3 1.1 607 22 169 107 408 70 8 12 0.3 161 2 HGV-3 Holister Qtz\Clay Vein 2 0.6 198 1 <5 161 295 49 2 29 <.05 62 3 HGV-4 Holister Qtz\Clay Vein 1 0.5 771 68 81 422 252 122 4 21 0.2 50 7 HSC-1 Holister Qtz\Clay Vein 418 1.1 1437 72 606 6082 392 1394 6 36 1.9 2604 3 HSC-2 Holister Qtz\Clay Vein 9 0.8 130 25 115 614 69 58 5 7 1.2 203 2 HSIN Holister Siliceous Sinter n/a <.5 6 2 <5 2 <5 2 11 368 >20 3 <1 MGCV-1 Midas Qtz\CC\Adl Vein 253 0.8 237 106 57 3002 <5 2 5 7 15.9 1013 <1 MGCV-2 Midas Qtz\CC\Adl Vein 429 0.5 96 22 29 3742 <5 <.5 3 <5 1.7 1254 <1 MCGC Midas Qtz\CC\Adl Vein 1511 0.7 4531 477 53 3276 <5 1 6 <5 4.1 3278 <1 MTGCG Midas Qtz\CC\Adl Vein 294 0.7 773 357 154 4974 <5 <.5 4 <5 15.6 2240 1 SMGK Sandman Adl Vein 1160 1.1 48 11 39 517 9 5 13 47 0.5 21 <1 SMGK-2 Sandman Adl Vein 2556 1.0 34 14 28 1363 9 3 8 30 0.3 7 2 SMGK-3 Sandman Host Rock 13 1.3 62 16 41 19 10 3 14 67 0.3 5 <1 SMP Sandman Qtz Vein 35 1.3 76 12 37 79 29 2 7 62 0.3 5 <1 HCN-1 Sandman Adl Vein 1540 0.9 17 4 16 708 <5 1 13 37 0.7 <2 <1 41 Table 2. Cont. Sample # Location Sample Type Au Mo Cu Pb Zn Ag As Sb Cr Ba Hg Se Te JUM1-1 Jumbo Adl Vein 906 0.5 37 5 35 591 10 16 5 27 0.7 <2 <1 JUM2-1 Jumbo Adl Vein 13 3.2 54 20 38 12 223 10 16 97 0.9 5 <1 JUM2-2 Jumbo Adl Vein 12 4.8 48 10 43 17 8 11 22 34 0.7 <2 <1 JUM2-3 Jumbo Qtz\Adl Vein 771 2.1 87 12 25 813 207 19 6 64 0.4 7 1 JUM3-1 Jumbo Adl Vein 9 3.4 72 26 233 6 364 52 9 53 0.5 47 <1 HCN-3OX Jumbo Adl Vein 415 1.1 11 1 15 299 <5 3 5 15 0.1 <2 <1 HCN-3RE Jumbo Adl Vein 597 0.8 6 2 <5 428 <5 2 4 14 0.3 <2 <1 JUM-1 Jumbo Qtz\Adl Vein 3748 6.1 157 65 66 1742 493 67 10 173 25.2 9 67 NEWA1-1 New Alma Qtz\Adl Vein 6 2.2 19 9 121 8 27 7 5 107 0.2 <2 <1 NEWA1-2 New Alma Qtz\Adl Vein 6 1.8 27 10 46 3 45 4 11 17 0.2 3 <1 NEWA1-3 New Alma Qtz\Adl Vein 0 0.8 10 6 32 1 32 2 7 21 0.1 <2 <1 NEWA2-1 New Alma Qtz Vein 0 2.0 19 26 61 1 32 4 14 33 0.1 <2 4 HCN-2 New Alma Adl Vein 175 <.5 4 4 <5 159 24 1 2 19 0.1 3 1 HCN-4 Ten Mile Adl Vein n/a 1.0 65 11 70 2 144 195 10 61 <.05 <2 <1 SLP-8 Sleper Qtz Vein 9788 4.3 277 82 62 5473 26 260 9 181 70.0 64 143 SLP-10 Sleper Qtz Vein 8599 1.8 272 51 96 3756 59 1692 6 25 47.0 27 18 KORYU-4 Koryu, Japan Qtz\Adl Vein 2211 1.3 35269 8458 6894 4224 599 344 7 9 0.7 5906 19 BG-2 Besie G, CO Qtz Vein 2289 2.2 1191 99 223 1463 149 377 12 640 >20 3 5300 SMCO Silverton, CO Qtz Vein 28767 8.0 15731 195700 7893 4797 23 148 18 173 3.2 7 137 CMCO Creson, CO Qtz Vein 7816 693.1 8939 1152 1896 2820 610 5560 4 881 1.5 11 10549 NMNV-1 Golden Age, CO Qtz Vein 1902 9.7 211 1712 110 229 198 40 13 200 1.6 <2 2296 VM-1 Vindicator, CO Qtz Vein 25136 2.6 207 390 57 6123 4987 760 6 49 58.0 39 28 BRM-1 Black Rose, CO Qtz Vein 3926 25.1 416 5016 157 2470 829 87 13 214 >20 3 6762 Notes: al deposits are located in the northern Great Basin unles otherwise indicated. Al data is in pm. Abreviations: Adl = adularia, C = calcite, Qtz = quartz. 42 Since the goal of this study was to evaluate the relative abundances of different elements in the ores of these systems, samples for geochemical analysis were ?high-graded? to contain the highest percentage of ore minerals possible and minimize the amount of gangue minerals and host rock. For this reason the concentration of each element is less important than the ratios and relative abundances compared to other elements. It should be noted that this practice of high-grading the samples could cause some elemental ratios to be inaccurate and further work is warranted to determine methods that will minimize this issue. It appears however, that the geochemistry of these ore samples was not grossly misrepresented. Geochemistry data amongst samples from the same deposit are generally quite consistent and; the results are consistent with the major ore minerals observed in hand samples and thin sections (described above). As a whole, samples are typical high-grade ore common to this type of epithermal deposit. Au concentrations greater than 1 ppm are present in nearly all of the samples and Ag concentrations generally exceed 100 ppm. The northern Great Basin deposits typically have higher precious metal to base metal ratios, compared to the deposits of Colorado and Japan. In the higher grade deposits of the northern Great Basin, Au and Ag concentrations far exceed base metal concentrations. The relatively lower grade samples typically have equal amounts of Ag and base metals with considerably less Au. The most notable difference that exists between deposits of different regions is the amounts of Au, Ag, Se and Te present. Deposits located in the northern Carlin Trend (Midas and Hollister), National district (National and Buckskin National), War Eagle Mountain, ID, and Koryu, Japan, all contain very Se-rich ores that are nearly devoid of Te along with typical Ag/Au ratios of >10 to 1. Conversely, the deposits of Colorado contain low levels 43 of Se, abundant Te, and Au concentrations that are often at least twice that of Ag. The deposits located in the Slumbering Hills (Jumbo, New Alma, Sandman, Sleeper, and Ten Mile) have ore chemistries considerably different from any of the other deposits in this study. The Au/Ag ratio is nearly 2 to 1 and all the deposits with the exception of Sleeper contain nearly no Se or Te, as well as having considerably lower base metal concentrations. Statistical Analysis A Pearson correlation matrix was calculated, using the limited geochemical data gathered for this study, for the northern Great Basin precious metal epithermal deposits. Although there are far too few data points to accurately characterize these deposits, results indicate several moderate to strong correlations between different elements. Plots were produced using both log normalized (Table 3) and ?raw? (Table 4) concentration data and show similar trends in elemental relationships. 44 Table 3. Correlation Matrix of Log Normalized Concentration Data Au Mo Cu Pb Zn Ag Ni Co Mo 0.336 Cu 0.123 0.149 Pb 0.099 0.176 0.722 Zn 0.113 0.383 0.632 0.793 Ag 0.625 -0.103 0.434 0.429 0.210 Ni -0.215 0.384 -0.069 -0.228 0.141 -0.539 Co -0.182 0.303 0.206 -0.091 0.289 -0.327 0.836 Mn 0.209 0.238 0.028 0.210 0.380 -0.096 0.004 0.129 Fe -0.091 0.506 0.147 0.128 0.393 -0.422 0.672 0.606 As -0.190 0.332 0.342 0.369 0.481 -0.111 0.427 0.483 Sr 0.187 0.142 -0.132 -0.321 -0.199 -0.108 0.164 0.251 Sb 0.096 0.380 0.395 0.361 0.456 0.228 0.351 0.361 Cr 0.217 0.687 0.044 0.185 0.306 -0.134 0.242 0.113 Ba 0.239 0.559 -0.119 -0.294 -0.008 -0.283 0.630 0.543 Hg 0.627 0.418 0.332 0.380 0.425 0.496 -0.186 -0.079 Se 0.119 -0.063 0.692 0.707 0.533 0.636 -0.483 -0.201 Te 0.244 0.249 0.366 0.271 0.194 0.414 0.083 0.230 Mn Fe As Sr Sb Cr Ba Hg Fe 0.149 As -0.126 0.601 Sr 0.298 0.279 -0.113 Sb -0.267 0.250 0.765 -0.249 Cr 0.188 0.422 0.328 -0.125 0.409 Ba 0.165 0.528 0.297 0.415 0.251 0.424 Hg 0.279 -0.004 0.178 0.161 0.460 0.394 0.132 Se -0.042 -0.224 0.134 -0.295 0.259 -0.082 -0.514 0.382 Te -0.160 0.010 0.191 0.179 0.352 -0.121 0.267 0.256 Se Te 0.191 Notes: Plot is a Pearson correlation matrix of log normalized geochemical data for the northern Great Basin deposits in this study (excludes the Colorado and Japan data). Correlations >0.5 are in bold. 45 Table 4. Correlation Matrix of Concentration Data Au Mo Cu Pb Zn Ag Ni Co Mo 0.551 Cu 0.409 0.094 Pb -0.051 -0.073 0.334 Zn -0.043 -0.066 0.335 0.999 Ag 0.352 0.145 0.408 -0.077 -0.071 Ni -0.062 0.101 -0.085 0.020 0.026 -0.262 Co -0.071 -0.128 -0.007 0.065 0.066 -0.175 0.480 Mn -0.071 -0.034 0.029 0.223 0.224 0.047 0.673 0.093 Fe -0.007 0.505 0.060 0.403 0.408 -0.204 0.123 0.028 As -0.038 -0.054 0.315 0.991 0.991 -0.120 0.026 0.071 Sr 0.024 0.429 -0.122 -0.071 -0.072 0.050 0.002 0.012 Sb 0.925 0.428 0.442 0.001 0.012 0.316 -0.051 -0.049 Cr 0.432 0.643 0.095 0.063 0.067 -0.043 -0.067 -0.223 Ba 0.324 0.694 -0.106 -0.119 -0.113 0.060 0.303 0.032 Hg 0.834 0.574 0.254 -0.062 -0.058 0.559 -0.110 -0.095 Se -0.066 -0.105 0.457 0.036 0.032 0.606 -0.166 -0.110 Te 0.258 0.470 -0.027 -0.037 -0.038 0.388 -0.057 -0.029 Mn Fe As Sr Sb Cr Ba Hg Fe 0.035 As 0.214 0.418 Sr -0.012 0.640 -0.065 Sb -0.069 -0.045 0.017 -0.086 Cr -0.109 0.192 0.080 -0.020 0.420 Ba 0.144 0.465 -0.086 0.513 0.113 0.310 Hg -0.012 0.004 -0.062 0.139 0.665 0.316 0.479 Se 0.080 -0.155 -0.022 -0.075 0.024 -0.063 -0.274 0.064 Te -0.068 0.185 -0.043 0.349 -0.015 0.016 0.710 0.629 Se Te -0.078 Notes: Plot is a Pearson correlation matrix of geochemical data for the northern Great Basin deposits in this study (excludes the Colorado and Japan data). Correlations >0.5 are in bold. 46 Gold shows a strong correlation (>0.8) with Hg and Sb along with moderate correlations (0.5 ? 0.8) with Ag and Mo. The strong Hg correlation fits well with field observations and published data that indicates cinnabar commonly occurs in the upper zones of these ore deposits (Vikre, 2007). Tetrahedrite ((Cu,Fe,Zn,Ag)12Sb4S13) is common in some ores, and may partially explain the strong Sb correlation. However, the weak correlation between Au and Cu suggests that Sb is contained in other minerals such as stibnite (Sb2S3), which is common in the upper zones of the veins in the National district (Lindgren, 1915; Vikre, 1984). The relationship with Ag is also to be expected as electrum is the most common Au-bearing ore mineral. The moderate correlation with Mo may indicate a connection to deeper porphyry systems, which are thought to act as sources of metal-bearing magmatic fluids (Hedenquist and Lowenstern, 1994). The strongest correlation for Ag is with Se (0.6), which is well supported by field observations and published data (Vikre, 1984; Halsor et al., 1988; Goldstrand and Schmidt, 2000) that indicate the Ag-minerals naumannite (Ag2Se) and aguilarite (Ag4SeS) are present in many of these deposits. Silver has a moderate correlation with Hg (0.5-0.6), likely for the same reason that gold does. Zinc shows a strong association with Pb. This is likely related to the base metal zones that commonly occur within these systems, generally below the precious metal zones. Field observations and petrography found abundant sphalerite and galena associated with some ore samples. Copper has moderate correlations with Pb, Zn and Se. Chalocopyrite is common in many of the polished thin sections that also contain other ore minerals. Copper has a weak correlation with Sb, As, and Ag, which is likely due to the 47 fact that tetrahedrite and tennantite ((Cu,Fe)12As4S13) are common in some of the deposits in this study. The relationship between As and Sb is weak to moderate as could be expected by examining the data (Table. 3). Whereas both elements are present in almost every sample, concentrations varied from sub-equal to inverse, thus no clear relationship is discernable here. By looking at the data in Table 3 a strong negative correlation between Te and Se could be expected, and that is the case if both the Nevada and Colorado ores are considered. However, if only the Nevada ores are considered, which are generally quite low in Te and enriched in Se, no clear correlation exists. Epithermal Trilinear Diagram Numerous classification schemes exist for epithermal deposits, and these schemes have been well summarized by Sillitoe and Hedenquist, (2003) and Simmons et al. (2005). Previous classification schemes have focused on alteration and gangue mineral assemblages, which are good indicators of the ore-forming fluid chemistry. However, a geochemical classification scheme for low-sulfidation ores has not been attempted. Trilinear diagrams are often used to characterize natural waters based on their major ionic species. In the classic Piper diagram, the cations Ca, Mg and Na + K are plotted onto one triangle and the anions Cl, SO4, and HCO3 + CO2 are plotted onto the other. When the points plotted in the triangles are projected into the quadrilateral field, differences in water chemistries can be clearly seen. Waters with similar sources and chemistries fall into the same area of the quadrilateral field. Dominant ions and 48 hydrochemical facies can be determined using a trilinear plot of major ions (Fetter, 2001). Thus, trilinear plots of water chemistry are useful for determining the natural water?s source and how the water chemistry has evolved. For this study, a trilinear diagram was modified such that the molar ratios of Au, Ag, and Pb/10 were normalized to 100% and then plotted in the metals triangle. Similarly the molar ratios of Se, Te, and Sb/10 + As/10 were normalized and then plotted in the metalloid triangle. The elements Pb, As, and Sb are common in epithermal ores and thus have higher background levels than Au, Ag, Se, and Te. For this reason the concentrations of Pb, As and Sb were reduced by a factor of 10 to compensate for the much more abundant elements. It should be noted that the ?raw data? with no factor 10 reductions were also plotted on a trilinear diagram with similar results, except that most of the trends observed were masked or subdued. By plotting all of the geochemical data from the epithermal ores (Nevada, Colorado, and Japan), on the new epithermal trilinear plot, it was determined that certain end-member compositions exist within the data as a whole. The two most prominent end members (Fig. 17) of these are the Au-telluride dominated ores of Colorado and the Ag-selenide dominated ?ginguro? ores found at deposits such as Midas, Hollister, War Eagle Mountain, Koryu, and Hishikari. A third group of deposits (National and Hog Ranch), which contain high levels of Pb, As, and Sb plot just to the left or within the Au-telluride field. 49 FIG. 17. Illustration of proposed fields for the modified trilinear diagram. Au-tellurides (yellow) and Ag- selenides (red). Chondritic meteorite data (Anders and Grevesse, 1989) are also plotted here (blue square) and are thought to mimic mantle chemistry (Winters, 2001), or at least early earth mantle. Geochemical District Descriptions National District: The National and Buckskin-National deposits both lie in the National district. Samples were collected from dumps around the numerous historical workings. Gold levels vary greatly in the National deposit ores, including some of the highest values (32,940 ppm) recorded for any sample in this study, and all Au levels are well over what could be considered ?ore grade.? Silver levels are slightly less variable ranging from 200 to 3800 ppm. Notably high levels of Pb, Zn, As, and Sb also are present in the ores. Selenium levels reach a maximum of 401 ppm and Te is nearly undetectable. When these data are plotted on the epithermal trilinear diagram (Fig. 18) it can be seen that As and Sb are the dominate metalloids in the National ores, and the amounts of Pb, 50 Au and Ag have a much higher degree of variability. The high degree of scatter, and range of minerals observed in the different samples collected, suggests more samples are needed to adequately characterize the National ores. The Buckskin-National ores share a similar geochemical signature to the National samples expect for a few notable dissimilarities. Gold concentrations are elevated in all samples (32 to 782 ppm) and Ag levels are exceptionally high (up to 3350 ppm). Significant levels of Pb, Zn, As and Sb are present but generally are an order of magnitude lower than those detected at National. Selenium levels are generally higher and there is no detectable Te in any of the samples. It is interesting to note that when the Buckskin National data are plotted on the epithermal trilinear diagram (Fig. 18) the data all plot neatly within the Ag-selenide field, unlike the National ores. War Eagle Mountain: The northern-most samples gathered during field work are from War Eagle Mountain, Silver City district, Idaho. Samples were collected from the numerous dumps surrounding historic workings, as well as from the outcropping Oro Fino vein. All the samples collected contained high levels of Au (up to 149 ppm) and Ag (up to 5700 ppm), as well as very high levels of Se (nearly 1700 ppm). Tellurium was generally below detection limits (<1 ppm) with a maximum of 18 ppm and Hg was not detected in any of the samples. The ores of War Eagle Mountian also plot on the epithermal trilinear diagram (Fig. 18) within the Ag-selenide field along with the ores from Buckskin National. 51 P b / 1 0 Au Te S b / 1 0 + A s / 1 0 Ag Te + S b / 1 0 + A s / 1 0 P b / 1 0 + A u Se 100 80 60 40 20 0 0 20 40 60 80 1 0 0 1 0 0 80 60 40 20 0 0 20 40 60 80 100 1 0 0 80 60 40 20 0 0 20 40 60 80 1 0 0 20 80 40 60 60 40 80 20 80 20 60 40 40 60 20 80 L e g e n d B u c k s k i n N a t i o n a l H o g R a n c h M u l e C a n y o n N a t i o n a l W a r E a g l e M o u n t a i n FIG. 18. Epithermal trilinear diagram of several northern Great Basin deposits showing the broad spectrum of ore chemistries. Hog Ranch (Bussey, 1996) and Mule Canyon (John et al., 2003) data are plotted for comparison. Note some of the Buckskin National data points are obscured by the overlapping War Eagle Mountain points. Northern Carlin Trend: The Midas deposit contains ores that closely resemble the ?ginguro? (silver-black) ores of many Japanese epithermal deposits such as Hishikari (Izawa et al., 1990). Abundant precious and base metal selenides have been reported at the Midas deposit as well as replacement textures of naumannite after base-metal sulfides (Golstrand and Schmidt, 2000). Samples were collected at the underground workings of the Ken Snyder mine, operated by Newmont Gold. Silver concentrations are remarkably consistent in all the samples analyzed for this study, ranging from approximately 3000- 5000 ppm. Gold values were more variable with a high of 1500 ppm and low of 250 ppm 52 and showed a positive correlation to the values of Se in each sample. Curiously low are As, Sb and Te which were all near or below detection limits. Samples from the Ivanhoe district were collected at the new underground workings in the Hollister Development Block, owned by Great Basin Gold. The samples collected show remarkable geochemical similarities to the ores at the nearby Midas mine. Extremely high Au (>400 ppm) and Ag (>6000 ppm) values were detected as well as high levels of Se (>2600 ppm) and low levels of Te (< 10 ppm). Abundant tetrahedrite and tennantite are present in hand samples, thus concentrations of As, Sb and Cu are high. Ores from the Midas and Hollister deposits plotted (Fig. 19) in or near the Ag- selenide field as expected. 80 20 60 40 40 60 20 80 20 80 40 60 60 40 80 20 1 0 0 80 60 40 20 0 0 20 40 60 80 1 0 0 100806040200 0 20 40 60 80 1 0 0 1 0 0 80 60 40 20 0 020406080100 Se P b / 1 0 + A u Te + S b / 1 0 + A s / 1 0 Ag S b / 1 0 + A s / 1 0 Te Au P b / 1 0 L e g e n d H o l l i s t e r M i d a s FIG. 19. Epithermal trilinear diagram of the Hollister and Midas deposits both of which plot within the Ag-selenide field. 53 Slumbering Hills: Within the Slumbering Hills and surrounding pediment are the Sleeper, Jumbo, New Alma, Sandman, and Ten Mile deposits. All have similar geochemical signatures and are known to have formed at around the same time (see below). The most recently exploited deposit in the area is Sleeper, which was mined from the mid-1980?s to mid-1990?s. Samples analyzed for this study have extremely high levels of Au and Ag with a ratio of nearly 2 to 1. Concentrations of Cu, Sb and Mn all range from 150 to 300 ppm. Sample SLP-10 also contained some of the highest levels of U recorded (18 ppm), possibly due to leaching from the rhyolite host rock. The Sleeper deposit was the only deposit in the Slumbering Hills to contain noteworthy levels of Se (27 - 64 ppm) and Te (18 - 143 ppm). Nearly all the samples from Jumbo, New Alma, Sandman, and Ten Mile contain very low or undetectable levels of Se and Te, and it appears they do not form any important ore minerals. The Jumbo and New Alma deposits lie just to the east of Sleeper in the northern Slumbering Hills. The general geochemical signature for both deposits is similar to that of Sleeper and their close proximity and similar ages suggest all three deposits are genetically linked. The Jumbo deposit has a Au/Ag ratio of approximately 2 to 1 with one sample having nearly 4000 ppm Au and several others having Au levels in the hundreds of ppm. Levels of Cu, Zn, Mn, As, and Sb all register in the tens to hundreds of ppm. The high manganese concentrations are likely due to the black oxide coating, which occurred on several of the samples from Jumbo and New Alma. New Alma samples generally have much lower overall Au and Ag numbers, most being less than 10 ppm, one high-grade sample did contain higher Au (175 ppm) and Ag 54 (159 ppm) levels, and generally samples had approximately equal amounts of Au and Ag. Relatively high levels of Cu, Zn, Mn and As were also present in similar ratios to the Jumbo samples. Manganese was especially high in these samples, which all had a black oxide coating on them. The Sandman deposit lies in the southern pediment of the Slumbering Hills. Recently it has been the subject of much exploration activity and is currently being drilled by Fronteer Development Group (Fronteer Development Group press releases 2007), which recently aquired it from New West Gold. Vein sets are predominately adularia and the only significant precious metal bearing mineral is electrum. The adularia veins contain high concentrations of Au (up to 2500 ppm) and Ag (up to 1300 ppm) and a similar Au/Ag ratio as the other Slumbering Hills deposits. Samples of host rock and quartz veins contain levels of Au and Ag ranging from 10 to 80 ppm. Base metals all occur in low levels (<100 ppm) and Mn (130 to 260 ppm) likely is present as a weathering product. The levels of As and Sb were also quite low, generally not exceeding 10 ppm. The Ten Mile district has been well described by Bowell et al. (2000). A sample split from the geochronology samples was submitted for geochemical analysis and yielded relatively low Ag levels (1.5 ppm). Levels of Cu (64 ppm), Zn (70) ppm, As (144 ppm) and Sb (195 ppm) were high considering the very low precious metal contents. This could be due to the very weathered nature of the sample. It was also noted by Bowell et al. (2000) that supergene processes played an important role in ore modification in this district. Gold concentrations were below detection limits, thus the Ten Mile data could not be plotted on the epithermal trilinear diagram. 55 If the geochemical data for the Slumbering Hills are considered as a whole, deposits throughout the region overlap somewhat in chemistry, but a distinct wide change can be observed between the northern deposits (Sleeper, Jumbo, New Alma) and the Sandman deposit, which sits in the southern pediment of the Slumbering Hills. The metals data are very tightly clustered in a field that indicates the ores are high in Au and Ag and generally very low in Pb. The large degree of scatter for these deposits, when projected into the quadrilateral section of the trilinear diagram (Fig. 20), is caused by a large variation in the metalloid content of the ores. 80 20 60 40 40 60 20 80 20 80 40 60 60 40 80 20 1 0 0 80 60 40 20 0 0 20 40 60 80 1 0 0 100806040200 0 20 40 60 80 1 0 0 1 0 0 80 60 40 20 0 020406080100 Se P b / 1 0 + A u Te + S b / 1 0 + A s / 1 0 Ag S b / 1 0 + A s / 1 0 Te Au P b / 1 0 L e g e n d J u m b o N e w A l m a S a n d m a n S l e e p e r FIG. 20. Epithermal trilinear diagram of Slumbering Hills area deposits shows a gradual change in deposit geochemistry from north to south. Japanese Epithermal Deposits: The Japanese epithermal precious metal deposits are considerably younger (~ 1 Ma) than the other deposits in this study (Sanematsu et al., 2006) and formed in a subduction related volcanic island arc tectonic setting (Izawa et al., 56 1990) that may be related to back-arc rifting (Garwin et al., 2005). However, texturally and chemically they have a number of similarities to the epithermal ores of the northern Great Basin, including banded quartz/adularia ? calcite veins, as well as abundant electrum and naumannite (Izawa et al., 1990). The sample from the Koryu deposit, Japan, is a classic example of ginguro ore consisting of quartz/adularia veins. For the present study the sample was high-graded to contain abundant naumannite and electrum. The geochemical composition of this sample is very similar to the other selenium dominated precious metal systems (Midas, Hollister, and War Eagle Mountain) in this study. As with the other deposits, this sample contains extremely high levels of Au (2200 ppm) and Ag (4200 ppm), along with abundant base metals, and high levels of As and Sb. Selenium is also very abundant (5900 ppm) and plays an important role in the formation of ore minerals. When data from this study and previously reported data from the Hishikari deposit (Izawa et al., 1990) were plotted, two clusters of data were created (Fig. 21). This distribution in some ways resembles that seen in the Slumbering Hills deposits. The metals data cluster close together and indicate roughly equal Au/Ag concentrations with very low levels of Pb. The metalloid data have a much larger spread that ranges from very Se-rich to very Sb and As-rich along with ubiquitous low Te levels. 57 P b / 1 0 Au Te S b / 1 0 + A s / 1 0 Ag Te + S b / 1 0 + A s / 1 0 P b / 1 0 + A u Se 100 80 60 40 20 0 0 20 40 60 80 1 0 0 1 0 0 80 60 40 20 0 0 20 40 60 80 100 1 0 0 80 60 40 20 0 0 20 40 60 80 1 0 0 20 80 40 60 60 40 80 20 80 20 60 40 40 60 20 80 L e g e n d H i s h i k a r i K o r y u FIG. 21. Epithermal trilinear diagram of Koryu and Hishikari, Japan (Izawa et al. 1990). Colorado Telluride Deposits: The Colorado ores included in this study represent the opposite end member in geochemical classification of low-sulfidation epithermal precious metal deposits. All samples were provided by James Saunders and Robert Cook (Golden Age) and consisted of quartz veins that had been sampled specifically to contain abundant Au/Ag-telluride minerals. A number of interesting similarities and differences can be observed between the selenide-dominated and telluride-dominated deposits. In the Colorado ores, Te levels can exceed 10,000 ppm while Se levels generally do not exceed 10 ppm. An interesting exception is the Vindicator mine sample, which had slightly more Se (39 ppm) than Te (28 ppm), along with some of the highest Au (25,000 ppm) and Ag (6000 ppm) levels of any sample. High levels of base metals along with Sb and As are 58 also present. The Cresson mine had notably abundant Mo (693 ppm), nearly two orders of magnitude greater than levels detected any other deposit in this study. As expected, all the Colorado telluride ores plot within the Au-telluride field (Fig. 22). Since only a few samples were used for this study, with the goal being that they serve as a basis for comparison, it is only possible to make general observations and inferences about what this data may mean for the classification system as a whole. It has been suggested that these Au-Te deposits represent a subclass of low-sulfidation epithermal deposits (Sillitoe and Hedenquist, 2003). 80 20 60 40 40 60 20 80 20 80 40 60 60 40 80 20 1 0 0 80 60 40 20 0 0 20 40 60 80 1 0 0 100806040200 0 20 40 60 80 1 0 0 1 0 0 80 60 40 20 0 020406080100 Se P b / 1 0 + A u Te + S b / 1 0 + A s / 1 0 Ag S b / 1 0 + A s / 1 0 Te Au P b / 1 0 L e g e n d B e s s i e G G o l d e n A g e B l a c k R o s e C r e s s o n S u n n y S i d e V i n d i c a t o r FIG. 22. Epithermal trilinear diagram of Colorado Au-telluride deposits which defines the telluride field. 59 GEOCHRONOLOGY One of the goals of this study was to provide new geochronology data for low- sulfidation precious metal epithermal deposits in the northern Great Basin that had either been significant historic producers or, as is the case of the Sandman deposit, may see future development. Through field work, adularia with inter-grown Au/Ag-minerals was obtained from four sites in and around the Slumbering Hills, Nevada (Jumbo, New Alma, Sandman, and Ten Mile) as well as two sites on War Eagle Mountain, Idaho. Since the overall aim of this study was to examine possible links between these mid-Miocene epithermal deposits and the initiation of the Yellowstone hotspot, the combination of closely clustered deposits in two broadly separated areas makes it possible to examine the timing of deposit formation on a local and regional scale. The geochronology results from this study augment previous studies for similar deposits in the region and thus provide more evidence that mineralization was coincident in time and space with the initiation of the Yellowstone hotspot. Geochronology Technique and Results The samples for this study were found to be highly radiogenic and contain a significant amount of extraneous 40Ar in surface defects and fluid inclusions (Appendix 2). Single crystal incremental heating was determined to be the most effective 60 method of analysis (see Methodology) for these samples as it allows for removal of extraneous 40Ar and evaluation of potential loss of accumulated radiogenic argon. Data reduction was preformed using the Excell add-on Isoplot (Ludwig, 2003) to create model-age spectrum and isotope correlation diagrams. The model-age spectrum and isotope correlation diagrams yield plateau and isochron ages respectively that are the same within uncertainty. However, the uncertainty of the isochron age is considerably higher (Appendix 2). The higher uncertainty of the isochron age reflects the fact that all analyses are highly radiogenic with little spread to define the regression, thus the plateau age is preferred. For this reason, only the release spectra (Table 5) for each deposit will be discussed in this thesis. When the ages determined in this study are compared to those from previous studies (Table 6) it is clear that these new data fall well within the expected time frame for mineralization within the area. A broad range of ages is present both for the entire region and within individual districts. This suggests that mineralization occurred throughout the region from approximately 16.5 Ma to 15.1 Ma with no discernable trend that would suggest mineralization started in one area and spread in any particular direction (Fig. 16). 61 Table 5. Summary of Geochronology Results Irradiation Location Plateau Age (Ma) Sample ID Deposit Filename Latitude Longitude HCN-1 Sandman au5.1a.adl.ih1 41? 03.959'N 118? 01.222'W 16.17 ? 0.03 au5.1a.adl.ih2 15.99 ? 0.04 au5.1a.adl.ih3 16.19 ? 0.04 au5.1a.adl.ih4 16.07 ? 0.04 au5.1a.adl.ih5 16.16 ? 0.04 Preferred Age 16.17 ? 0.04 HCN-2 New Alma au5.1c.adl.ih.1 41? 17.857'N 118? 00.362'W 15.86 ? 0.04 au5.1c.adl.ih.2 16.04 ? 0.02 au5.1c.adl.ih.3 16.05 ? 0.03 au5.1c.adl.ih.4 no plateau au5.1c.adl.ih.5 15.99 ? 0.03 Preferred Age 16.03 ? 0.07 HCN-3RE Jumbo au5.1f.adl.ih1 41? 18.475'N 118? 01.228'W 16.54 ? 0.04 au5.1f.adl.ih2 no plateau au5.1f.adl.ih3 16.53 ? 0.03 au5.1f.adl.ih4 16.54 ? 0.05 au5.1f.adl.ih5 no plateau Preferred Age 16.53 ? 0.04 HCN-4 Ten Mile au5.1h.adl.ih1 40? 58.577'N 117? 54.510'W 16.50 ? 0.03 au5.1h.adl.ih2 16.42 ? 0.03 au5.1h.adl.ih3 no plateau au5.1h.adl.ih4 16.53 ? 0.03 au5.1h.adl.ih5 no plateau Preferred Age 16.52 ? 0.04 OF-1 War Eagle Mtn. au3.3d.adl.31 43? 00.669'N 116? 41.857'W 16.32 ? 0.03 au3.3d.adl.32 16.31 ? 0.03 au3.3d.adl.33 16.21 ? 0.04 au3.3d.adl.34 16.09 ? 0.04 au3.3d.adl.35 16.08 ? 0.04 Preferred Age 16.31 ? 0.04 WEMS3-1 War Eagle Mtn. au8.2c.adl.41 43? 00.339'N 116? 41.926'W 15.55 ? 0.04 au8.2c.adl.42 15.66 ? 0.03 au8.2c.adl.43 15.55 ? 0.04 au8.2c.adl.44 15.67 ? 0.04 au8.2c.adl.45 15.78 ? 0.05 Preferred Age 15.61 ? 0.10 Notes: Uncertainties are one standard deviation. The preferred age was calculated using a weighted average. Irradiation filenames correspond to an analysis of a single crystal. See Appendix 2 for full analytical data and Appendix 3 for J-values. 62 Table 6. Revised Geochronology of mid-Miocene Au-Ag Deposits in the Northern Great Basin Dating Predominant Deposit Age ? 1? (Ma) Method Host Rocks Reference Jumbo 17.3 ? 0.5 K/Ar metasediments Conrad et al., 1993 War Eagle Mtn. 16.6-15.2 K/Ar granite Halsor et al., 1988 Jumbo 16.53 ? 0.04 Ar/Ar metasediments this study Ten Mile 16.52 ? 0.04 Ar/Ar metasediments this study War Eagle Mtn. 1 16.31 ? 0.04 Ar/Ar granite this study Sandman 16.17 ? 0.04 Ar/Ar granite this study Sleeper 16.1-14.3 ? 0.07 Ar/Ar rhyolite Conrad and McKee, 1996 New Alma 16.03 ? 0.03 Ar/Ar metasediments this study Buckskin National 15.8-15.4 ? 0.2 K/Ar rhyolite Vikre, 1985 DeLamar, ID 15.7 ? 0.5 K/Ar rhyolite Halsor et al., 1988 War Eagle Mtn. 3 15.61 ? 0.1 Ar/Ar granite this study Mule Canyon 15.6 ? 0.04 Ar/Ar rhyolite John et al., 2003 McDermitt (Hg) 15.6 ? 0.4 K/Ar rhyolite Noble et al., 1988 Midas 15.4-15.3 ? 0.08 Ar/Ar rhyolite Leavitt et al., 2004 Hog Ranch 15.2-14.8 ? 0.4 K/Ar rhyolite Bussey, 1996 Hollister 15.19 ? 0.05 Ar/Ar rhyolite Peppard, 2002 Seven Troughs 13.82 ? 0.02 Ar/Ar rhyolite Hudson et al., 2006 Notes: War Eagle Mtn. 1 refers to the Oro Fino vein, War Eagle Mtn. 3 refers to sample site 3 in this study. McDermitt is an epithermal mercury deposit. Slumbering Hills Deposits The deposits located in and around the Slumbering Hills that were dated for this study (Fig. 23) are the Sandman, New Alma, Jumbo, and Ten Mile deposits. 63 Jumb o N ew A l ma S a nd ma n T en M i l e S l u mb e r i n g H i l l s 41 ? N 118 ? W S l e ep er 1 0 k m N Sandman: The Sandman deposit defines an area that sits in the southern pediment of the Slumbering Hills. The area has been the subject of a number of exploration projects and is currently being explored for epithermal precious metal mineralization. Samples collected for this study consist of silicified tuff with thin (up to 4 mm) adularia veins and fracture encrustations that contained abundant visible gold. Five crystals from geochemistry sample HCN-1 were analyzed by incremental heating and produced plateau ages (Fig. 24) with a range of 16.19 ? 0.04 to 15.99 ? 0.04 Ma. A preferred age of 16.17 ? 0.04 Ma was determined by calculating the weighted average of the three oldest crystals. At the 95% confidence level, there is 85% chance that the spread of those three plateau ages are consistent with a normal distribution of FIG. 23. Map of Slumbering Hills area deposits. Modified from Wendt (2003). 64 errors in precision. As with the other Slumbering Hills deposits, the veins at Sandman are generally not more than a few centimeters wide; therefore, it is unlikely that a significant amount of time elapsed between the depositions of different crystals. The significantly younger ages of the two crystals excluded from the preferred age calculation likely reflect alteration or a higher diffusivity of 40Ar. In either case the loss of Ar would cause the crystals to yield erroneously young ages. Field observations support this conclusion as many samples from Sandman have a thin coating of clay over the euhedral adularia crystals (Fig.5). 65 FIG. 24. Release spectrum and plateau ages for five single adularia crystals (14-20 mesh size, 1.2- 0.75 mm) of sample HCN-1 from the Sandman deposit. Steps used to define the plateau are shaded. Errors for individual steps and plateau ages are at 1?. See Appendix 2 for incremental heating data. Irradiation filenames are as follows: A) au5.1a.adl.ih1, B) au5.1a.adl.ih2, C) au5.1a.adl.ih3, D) au5.1a.adl.ih4, and E) au5.1a.adl.ih1. 8 12 16 20 24 28 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C umulat i v e 39 A r Frac t i on A ge ( M a) P l a t e a u a g e = 1 6 . 0 6 5 ? 0 . 0 4 4 M a M S W D = 0 . 8 5 , p r o b a b i l i t y=0 . 5 7 I n cl u d e s 1 0 0 % o f t h e 39 Ar 8 12 16 20 24 28 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C umulat i v e 39 A r Frac t i on A ge ( M a) P l a t e a u a g e = 1 6 . 1 8 7 ? 0 . 0 4 4 M a M S W D = 0 . 4 5 , p r o b a b i l i t y=0 . 7 2 I n cl u d e s 6 3 % o f t h e 39 Ar 8 12 16 20 24 28 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C umulat i v e 39 A r Frac t i on A ge ( M a) P l a t e a u a g e = 1 5 . 9 8 7 ? 0 . 0 4 4 M a M S W D = 0 . 4 6 , p r o b a b i l i t y=0 . 8 9 I n cl u d e s 9 6 . 8 % o f t h e 39 Ar 8 12 16 20 24 28 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C umulat i v e 39 A r Frac t i on A ge ( M a) P l a t e a u a g e = 1 6 . 1 6 8 ? 0 . 0 3 2 M a M S W D = 0 . 7 4 , p r o b a b i l i t y=0 . 7 2 I n cl u d e s 1 0 0 % o f t h e 39 Ar 8 12 16 20 24 28 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C umulat i v e 39 A r Frac t i on A ge ( M a) P l a t e a u a g e = 1 6 . 1 5 5 ? 0 . 0 3 8 M a M S W D = 1 . 3 , p r o b a b i l i t y=0 . 2 3 I n cl u d e s 1 0 0 % o f t h e 39 Ar A B C D E 66 New Alma: The New Alma deposit sits just south of the old Jumbo mine workings in the Slumbering Hills. Four of the five adularia crystals analyzed produced plateau ages that range from 16.05 ? 0.03 to 15.86 ? 0.04 Ma (Fig. 25). The one crystal that did not produce a plateau age (au5.1c.adl.ih4) still yields individual heating increment ages that are consistent within uncertainty of the other samples (Appendix 2). The preferred age, calculated using a weighted average of the oldest three plateau ages, is 16.03 ? 0.07 Ma. The significantly younger age of one crystal, 15.86 ? 0.04 Ma, excluded from the preferred age calculation likely reflects loss of Ar due to alteration. At the 95% confidence level, there is 26% probability that the spread of plateau ages of the three oldest crystals are consistent with a normal distribution of errors in precision. However, if all four crystals are averaged, this probability drops to 0.1%. This indicates that statistically it is highly unlikely the difference in ages is due to errors in precision alone. Thus, the crystals are either of different ages or some have been subject to Ar loss. The very thin nature of the adularia veins makes more than one generation of crystals unlikely in these samples. Field observations suggest that the samples taken from New Alma have undergone intense surface oxidation and are coated in a Fe-oxide and/or Mn-oxide coating. Thus it seems likely that late oxidation caused loss of Ar in some of the crystals. 67 FIG. 25. Release spectrum and plateau ages for five single adularia crystals (14-20 mesh size, 1.2- 0.75 mm) of sample HCN-2 from the New Alma deposit. Steps used to define the plateau are shaded. Errors for individual steps and plateau ages are at 1?. See Appendix 2 for incremental heating data. Irradiation filenames are as follows: A) au5.1c.adl.ih1, B) au5.1c.adl.ih2, C) au5.1c.adl.ih3, D) au5.1c.adl.ih4, and E) au5.1c.adl.ih1. 8 12 16 20 24 28 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C umulat i v e 39 A r Frac t i on A ge ( M a) 8 12 16 20 24 28 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C umulat i v e 39 A r Frac t i on A ge ( M a) P l a t e a u a g e = 1 6 . 0 5 4 ? 0 . 0 2 7 M a M S W D = 1 . 0 9 , p r o b a b i l i t y=0 . 3 7 I n cl u d e s 9 2 % o f t h e 39 Ar 8 12 16 20 24 28 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C umulat i v e 39 A r Frac t i on A ge ( M a) P l a t e a u a g e = 1 6 . 0 3 7 ? 0 . 0 2 2 M a M S W D = 1 . 4 , p r o b a b i l i t y=0 . 1 9 I n cl u d e s 9 2 % o f t h e 39 Ar 8 12 16 20 24 28 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C umulat i v e 39 A r Frac t i on A ge ( M a) P l a t e a u a g e = 1 5 . 8 6 4 ? 0 . 0 4 2 M a M S W D = 0 . 9 6 , p r o b a b i l i t y=0 . 4 6 I n cl u d e s 9 4 . 9 % o f t h e 39 Ar 8 12 16 20 24 28 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C umulat i v e 39 A r Frac t i on A ge ( M a) P l a t e a u a g e = 1 5 . 9 9 4 ? 0 . 0 2 7 M a M S W D = 1 . 2 , p r o b a b i l i t y=0 . 2 8 I n cl u d e s 8 1 . 1 % o f t h e 39 Ar A B C D E 68 Jumbo: The Jumbo deposit sits in the northern Slumbering Hills just to the east of the Sleeper mine. The Jumbo deposit is the only deposit examined in the Slumbering Hills that has previously been dated. A study by Conrad et al. (1993), using K/Ar methods, determined that adularia in veins had an age of 17.3 Ma. However, the bulk- sample total-fusion techniques used in that study are inherently limited because of their inability to resolve potential contributions from various sources of extraneous argon (inherited ?excess? 40Ar, or other non-atmospheric argon). Thus, it was decided a reexamination of the Jumbo deposit using improved techniques was warranted. Of the five adularia crystals analyzed in this study, three yield plateau ages (Fig. 26). Plateau ages for these three crystals overlap within uncertainties and yield a preferred age of 16.53 ? 0.04 Ma. The majority of the heating increments for the other two crystals fall within 2? of this age (Appendix 2). The new data suggest that the earlier result for Jumbo appears anomalously old due to an unresolved component of extraneous 40Ar. Evidence for this can be observed in Appendix 2 and Figure 26, by noting that the initial or final steps of each incremental heating schedule contain generally high levels of 40Ar, low radiogenic yields, and older calculated ages than expected. This is likely due to extraneous 40Ar trapped on the surface or in fluid inclusions. 69 FIG. 26. Release spectrum and plateau ages for five single adularia crystals (14-20 mesh size, 1.2- 0.75 mm) of sample HCN-3RE from the Jumbo deposit. Steps used to define the plateau are shaded. Errors for individual steps and plateau ages are at 1?. See Appendix 2 for incremental heating data. Irradiation filenames are as follows: A) au5.1f.adl.ih1, B) au5.1f.adl.ih2, C) au5.1f.adl.ih3, D) au5.1f.adl.ih4, and E) au5.1f.adl.ih1. Note anomalously old ages in initial or final increments of the analysis (arrows) consistent with release of extraneous ?excess? 40Ar. 8 12 16 20 24 28 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C umulat i v e 39 A r Frac t i on A ge ( M a) P l a t e a u a g e = 1 6 . 5 3 7 ? 0 . 0 5 0 M a M S W D = 1 . 5 , p r o b a b i l i t y=0 . 1 6 I n cl u d e s 9 3 . 1 % o f t h e 39 Ar 8 12 16 20 24 28 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C umulat i v e 39 A r Frac t i on A ge ( M a) P l a t e a u a g e = 1 6 . 5 2 9 ? 0 . 0 2 9 M a M S W D = 1 . 6 , p r o b a b i l i t y=0 . 0 8 3 I n cl u d e s 9 9 . 4 5 % o f t h e 39 Ar 8 12 16 20 24 28 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C umulat i v e 39 A r Frac t i on A ge ( M a) 8 12 16 20 24 28 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C umulat i v e 39 A r Frac t i on A ge ( M a) P l a t e a u a g e = 1 6 . 5 3 8 ? 0 . 0 3 6 M a M S W D = 0 . 6 4 , p r o b a b i l i t y=0 . 7 0 I n cl u d e s 6 2 . 9 % o f t h e 39 Ar 8 12 16 20 24 28 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C umulat i v e 39 A r Frac t i on A ge ( M a) A B C D E 70 Ten Mile: The Ten Mile district sits to the south east of the Slumbering Hills and just to the north of the town of Winnemucca, Nevada. Plateau ages from three samples (Fig. 27) range from 16.53 ? 0.03 to 16.42 ? 0.03 Ma. The two crystals that did not generate a plateau age still had incremental heating steps that yielded ages within this range (Appendix 2). A weighted average of the two oldest crystals yields a preferred age of 16.52 ? 0.04 Ma. All samples collect at the Ten Mile deposit are highly oxidized making material suitable for dating difficult to obtain. This is likely the reason for the younger age of the excluded plateau age and the reason why the other two crystals did not generate plateau ages. There also is a significant component of excess 40Ar in some the samples. In these samples the first and last few heating increments have very low radiogenic yields and extremely old calculated ages (Appendix 2). Consequently, the samples from Ten Mile are not ideal for geochronology work. However, careful examination of the data allows for a reasonable and reliable age to be interpreted from these less than desirable samples. 71 FIG. 27. Release spectrum and plateau ages for five single adularia crystals (14-20 mesh size, 1.2-0.75 mm) of sample HCN-4 from the Ten Mile deposit. Steps used to define the plateau are shaded. Errors for individual steps and plateau ages are at 1?. See Appendix 2 for incremental heating data. Irradiation filenames are as follows: A) au5.1h.adl.ih1, B) au5.1h.adl.ih2, C) au5.1h.adl.ih3, D) au5.1h.adl.ih4, and E) au5.1h.adl.ih1. Note anomalously old ages in initial or final increments of some analysis (arrows) consistent with release of extraneous ?excess? 40Ar. 8 12 16 20 24 28 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C umulat i v e 39 A r Frac t i on A ge ( M a) P l a t e a u a g e = 1 6 . 5 2 8 ? 0 . 0 2 9 M a M S W D = 1 . 5 , p r o b a b i l i t y=0 . 2 1 I n cl u d e s 7 9 . 5 % o f t h e 39 Ar 8 12 16 20 24 28 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C umulat i v e 39 A r Frac t i on A ge ( M a) 8 12 16 20 24 28 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C umulat i v e 39 A r Frac t i on A ge ( M a) P l a t e a u a g e = 1 6 . 4 2 3 ? 0 . 0 2 5 M a M S W D = 1 . 6 , p r o b a b i l i t y=0 . 1 4 I n cl u d e s 8 9 . 3 % o f t h e 39 Ar 8 12 16 20 24 28 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C umulat i v e 39 A r Frac t i on A ge ( M a) P l a t e a u a g e = 1 6 . 5 0 1 ? 0 . 0 2 9 M a M S W D = 0 . 5 5 , p r o b a b i l i t y=0 . 7 4 I n cl u d e s 7 4 . 2 % o f t h 39 Ar 8 12 16 20 24 28 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C umulat i v e 39 A r Frac t i on A ge ( M a) A B C D E 72 War Eagle Mountain Deposit War Eagle Mountain sits in the Silver City district of southwestern Idaho. The area has been the site of precious metal mining for well over a hundred years and numerous historic workings cover War Eagle Mountain (Fig. 28). Samples suitable for dating were collected from a vein outcrop directly beneath the Oro Fino mine (OF-1) and another unnamed adit located ~0.5 km southwest (WEMS3-1). Previous work by Halsor et al. (1988) using K-Ar methods, determined that adularia from veins on War Eagle Mountain range in age from 16.6 to 15.2 Ma. FIG. 28. Map of sample locations of OF-1 and WEMS3-1 taken from historic workings on War Eagle Mountain. Contour lines are labeled in feet. Modified from USGS DeLamar Quadrangle Topography Map. WEMS3-1 OF-1 0.5 km N 73 Plateau ages were determined for all ten crystals analyzed from War Eagle Mountain. Sample OF-1 from the Oro Fino vein generated plateau ages that range from 16.32 ? 0.03 to 16.08 ? 0.04 Ma (Fig. 29). A weighted average of the oldest two plateau ages yields a preferred age of 16.31 ? 0.04 Ma. Plateau ages from sample WEMS3-1 range from 15.78 ? 0.05 to 15.55 ? 0.04 Ma (Fig. 30). A preferred age of 15.63 ? 0.11 Ma was calculated using the youngest four plateau ages because they overlap at 2?. The oldest plateau age appears to contain some component of excess 40Ar (Fig. 30 E) that may have caused it to appear anomalously old. The characteristics of the War Eagle Mountain deposit are different from those of the Slumbering Hills. The wide range of ages for samples from War Eagle Mountain implies the system was long lived. The veins that host precious metals are much thicker (1-2 m) and show evidence of many deposition and brecciation events. The data generated by this study and previous work suggest the hydrothermal system on War Eagle Mountain was active for at least 600,000 years. 74 FIG. 29. Release spectrum and plateau ages for five single adularia crystals (14-20 mesh size, 1.2- 0.75 mm) of sample OF-1 from the Oro Fino vein. Steps used to define the plateau are shaded. Errors for individual steps and plateau ages are at 1?. See Appendix 2 for incremental heating data. Irradiation filenames are as follows: A) au8.adl.31, B) au8.adl.32, C) au8.adl.33, D) au8.adl.34, and E) au8.adl.35. 8 12 16 20 24 28 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C umulat i v e 39 A r Frac t i on A ge ( M a) P l a t e a u a g e = 1 6 . 0 9 3 ? 0 . 0 3 8 M a M S W D = 1 . 4 , p r o b a b i l i t y=0 . 1 1 I n cl u d e s 9 6 . 5 % o f t h e 39 Ar 8 12 16 20 24 28 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C umulat i v e 39 A r Frac t i on A ge ( M a) P l a t e a u a g e = 1 6 . 2 1 2 ? 0 . 0 3 5 M a M S W D = 0 . 4 0 , p r o b a b i l i t y=0 . 9 1 I n cl u d e s 9 1 . 3 % o f t h 39 Ar 8 12 16 20 24 28 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C umulat i v e 39 A r Frac t i on A ge ( M a) P l a t e a u a g e = 1 6 . 3 0 6 ? 0 . 0 2 9 M a M S W D = 0 . 9 2 , p r o b a b i l i t y=0 . 5 0 I n cl u d e s 6 7 . 1 % o f t h e 39 Ar 8 12 16 20 24 28 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C umulat i v e 39 A r Frac t i on A ge ( M a) P l a t e a u a g e = 1 6 . 3 2 1 ? 0 . 0 2 8 M a M S W D = 1 . 4 , p r o b a b i l i t y=0 . 1 5 I n cl u d e s 9 9 . 7 1 % o f t h e 39 Ar 8 12 16 20 24 28 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C umulat i v e 39 A r Frac t i on A ge ( M a) P l a t e a u a g e = 1 6 . 0 8 2 ? 0 . 0 4 1 M a M S W D = 0 . 4 0 , p r o b a b i l i t y=0 . 9 5 I n cl u d e s 1 0 0 % o f t h e 39 Ar A B C D E 75 FIG. 30. Release spectrum and plateau ages for five single adularia crystals (14-20 mesh size, 1.2- 0.75 mm) of sample WEMS3-1 from War Eagle Moutain site 3. Steps used to define the plateau are shaded. Errors for individual steps and plateau ages are at 1?. See Appendix 2 for incremental heating data. Irradiation filenames are as follows: A) au8.adl.41, B) au8.adl.42, C) au8.adl.43, D) au8.adl.44, and E) au8.adl.45. Note anomalously old ages in initial or final increments of analysis E (arrows) consistent with release of extraneous ?excess? 40Ar. 8 12 16 20 24 28 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C umulat i v e 39 A r Frac t i on A ge ( M a) P l a t e a u a g e = 1 5 . 6 6 6 ? 0 . 0 3 5 M a M S W D = 0 . 5 7 , p r o b a b i l i t y=0 . 7 8 I n cl u d e s 1 0 0 % o f t h e 39 Ar 8 12 16 20 24 28 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 Cu m u lat iv e 39 A r F r ac t io n Ag e ( M a) P l a t e a u a g e = 1 5 . 5 5 1 ? 0 . 0 3 5 M a M S W D = 1 . 5 , p r o b a b i l i t y=0 . 1 0 I n cl u d e s 9 9 . 4 7 % o f t h e 39 Ar 8 12 16 20 24 28 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C umulat i v e 39 A r Frac t i on A ge ( M a) P l a t e a u a g e = 1 5 . 6 5 9 ? 0 . 0 3 3 M a M S W D = 0 . 8 8 , p r o b a b i l i t y=0 . 5 7 I n cl u d e s 8 5 . 1 % o f t h e 39 Ar 8 12 16 20 24 28 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C umulat i v e 39 A r Frac t i on A ge ( M a) P l a t e a u a g e = 1 5 . 5 4 6 ? 0 . 0 3 7 M a M S W D = 1 . 0 5 , p r o b a b i l i t y=0 . 4 0 I n cl u d e s 1 0 0 % o f t h e 39 Ar 8 12 16 20 24 28 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C umulat i v e 39 A r Frac t i on A ge ( M a) P l a t e a u a g e = 1 5 . 7 8 0 ? 0 . 0 4 8 M a M S W D = 1 . 1 9 , p r o b a b i l i t y=0 . 2 8 I n cl u d e s 9 7 . 1 % o f t h e 39 Ar A B C D E 76 DISCUSSION Ore Petrography A number of different interpretations have been made about the ore textures present in low-sulfidation epithermal deposits. Recent evidence indicates Au is transported from a deeper porphyry environment into the epithermal environment (Heinrich et al., 2004; Heinrich, 2005; Simmons and Brown, 2006). Banding of ore minerals could represent pulses of precious metal bearing magmatic fluids that mixed with heated meteoric water and rapidly changed the equilibrium causing precipitation of ore minerals. The presence of dendritic ore minerals and/or jig saw quartz in many of the samples indicates that rapid precipitation from a supersaturated solution is a common occurrence in these epithermal systems. Rather than periods of boiling caused by sealing and reopening of fluid conduits by precipitation of quartz, followed by pressure release due to a critical increase in pressure or seismic activity (Guilbert and Park, 1985), it is likely these systems are essentially always boiling and pseudomorphic quartz textures could simply indicate equilibrium changes that occurred in the boiling zone. The presence of adularia as the dominant or even exclusive vein material in some deposits is somewhat of a geochemical conundrum. It has been suggested that adularia forms at the expense of quartz due to the higher solubility of quartz under alkaline conditions (Sillitoe, 2002). Fluids in low-sulfidation epithermal systems are widely considered to be near-neutral pH, low-salinity chloride-dominated solutions, which 77 would likely not easily transport the required aluminum to form adularia. Field observations in this study indicate that all of the ?adularia-only? deposits are hosted or underlain by argillaceous-metasedimentary or granitic rocks. These rocks could serve as an abundant source of aluminum and potassium and thus allow for supersaturation of aluminum and potassium at depth, causing adularia rather than quartz to form as the primary vein material. This scenario likely would require lower pH fluids and steam- heated groundwater to leach the required aluminum and potassium. The adularia-only deposits also contain electrum almost exclusively as the precious metal mineral with very little selenide or sulfide minerals, suggesting different geochemical conditions from the selenide/sulfide-rich deposits. Adularia is present in both electrum-dominated and selenide/sulfide-dominated deposits. This may indicate that different factors control precious metal mineralogy (magmas?) and adularia precipitation (host rocks?). Further work investigating how host rocks affect vein mineralogy and styles of mineralization in low-sulfidation ores is warranted. Geochemistry The deposits in this study within the same district or sub-region have generally similar but not necessarily the same geochemistries. The Slumbering Hills area deposits (Jumbo, New Alma, Sandman, Sleeper and Ten Mile) all have high Au to Ag ratios, electrum as the primary precious metal mineral, low base metal contents, and relatively low to undetectable amounts of Se or Te. The Midas and Hollister deposits, which are both located on the northern part of the Carlin trend, also have very similar geochemical signatures including: high Ag to Au ratios, relatively high base metal contents, high 78 levels of Se and very low Te, along with Ag-selenides, sulfides and sulfosalts as the dominate precious metal minerals. These geochemical similarities coupled with the fact that all of the above spatially related deposits formed within a time span of ~0.5 Ma, suggests that similar geologic processes were operating throughout the region on a district-wide or even larger scale. Additionally, there are important exploration implications as both areas likely host similar undiscovered ?blind? deposits. Other spatially related deposits such as National and Buckskin National have a larger degree of geochemical variation between them. A wider suite of samples is needed to fully quantify their geochemical differences. However, a number of processes could explain the variability present between these two deposits (see below). On a broader regional scale the deposits of the northern Great Basin fall within or near the Ag-selenide end member of the epithermal trilinear diagram, whereas the Colorado deposits plot at or near the Au- telluride end member. This suggests that both regional and local-scale geologic processes described in detail in the literature clearly also have a profound impact on ore chemistry. In addition to the geochemical consistency amongst spatially related deposits, geochemical correlations further support the theory that the majority of the precious metals and some base metals in epithermal systems have a common source. A statistical analysis of just the northern Great Basin deposits indicates that Au has a strong to moderate statistical correlation with Hg, Sb, Ag, and Mo. A strong correlation also exists between Ag and Se. Experimental heating of chondritic meteorites, which are thought to approximate the composition of the mantle (Winters, 2001), found that As, Hg, S, Sb, Se, Te, and locally Cd were preferentially released at atmospheric pressures and temperatures of 200-900? C (Lauretta et al., 2002). Another study found that Au had similar volatility 79 to Hg (Lauretta et al., 2001). This suggests that these elements could be released together during a process such as mantle distillation or magma degassing. A study by Saunders and Romberger (1985) suggested that Te can play an important role in Au transport in Au-telluride epithermal deposits and that fluids in these deposits have a significant magmatic signature. A more recent study found that a substantial amount of Au can be transported by a sulfur-dominated vapor under experimental conditions similar to those in the upper mantle (Peregoedova et al., 2006). These data coupled with the recent evidence that Au is transported from the deeper porphyry environment to the epithermal environment (Heinrich et al., 2004; Heinrich, 2005; Simmons and Brown, 2006) suggests that many of the ?epithermal suite? elements in these systems may have a magmatic source. Geochronology There is mounting evidence that low-sulfidation epithermal deposits form relatively quickly. Data from this study and others (see Mining District Geology) indicates low-sulfidation epithermal systems in the northern Great Basin were active on a district wide scale for 0.3 to 0.6 Ma. A recent study of the Hosen-1 vein at the Hishikari deposit, Japan, found that the time interval from the margin to the center of the 2 m wide vein was about 260,000 years, and that vein formation occurred episodically with intervals of 30,000 to 110,000 years separating individual mineralizing events (Sanematsu et al., 2006). Another study that examined gold in magmatic hydrothermal solutions at the Ladolam hydrothermal system, Papua New Guinea, estimated that the huge gold deposit there could have formed within 55,000 years (Simmons and Brown, 80 2006). In the northern Great Basin, spatially related deposits such as those in the Slumbering Hills, northern Carlin Trend, or War Eagle Mountain have a maximum variation in age of around 600,000 years. In this study, uncertainty in age measurements range from 20,000 to 50,000 years, and variations between individual crystals for each deposit range from 0.1 to 1 Ma. These data indicate that future geochronology work should be conducted with the understanding that the difference in time between individual mineralizing events may approach the margin of uncertainty of current geochronology methods. Within sample groups some plateau ages do not overlap, this may be explained by the analysis of crystals individually, rather than a group of crystals as a bulk sample. If a bulk sample had been analyzed the imperfections in individual crystals, such as excess Ar or loss of Ar due to weathering, would likely have been masked. Thus, a more ?average? gas composition would have been analyzed. This average gas composition would not likely give the correct age for a deposit but rather an age that was slightly older or younger, and the effects of Ar gain or loss would be masked such that it may not be detectable. By using a smaller amount of material (single crystals) with an instrument designed to analyze the smaller sample, less error is introduced into the measurement and a more accurate age can be determined. The single crystals ages for each sample can be viewed as a group and a weighted averaged used to calculate a preferred age. Using this method, crystals that yield statistically anomalous ages or show signs of Ar gain or loss can be ignored. If these same crystals had been part of a bulk sample, they may have adversely affected the accuracy of the analysis, yet this effect may not have been obvious. 81 For the purposes of understanding the formation of these deposits, precision may be less important than the geologic ?accuracy.? If the loss of 40Ar has been heterogeneous in a given population of crystals, then the precise average for a group (bulk sample) may have less meaning than an accurate range of ages. Examination of sample petrography including alteration effects, or evidences for multiple vein forming events, can give geologic context to the range of ages and make them more meaningful. 82 CONCLUSIONS A number of lines of evidence suggest that mid-Miocene low-sulfidation epithermal precious metal mineralization in the northern Great Basin is related to the initial development of the Yellowstone hotspot. The mineralogy and geochemistry for the northern Great Basin deposits examined in this study show remarkable similarities, and may indicate a common source for the major metal and metalloid ore components. The earliest volcanism associated with the Yellowstone hotspot occurs in the nearby Steens Mountain basalts at 16.59 ? 0.10 Ma (Brueseke et al, 2007). The redefined age for the Jumbo deposit of 16.53 ? 0.04 Ma makes it the oldest known low-sulfidation deposit in the northern Great Basin, and clearly indicates mineralization began shortly after the first volcanism related to the Yellowstone hotspot. The data generated by this study and others indicates that mineralization continued at a reasonably steady rate until at least 15.1 Ma. Ore petrography compliments other studies and indicates that the deposits in this study contain precious metals as electrum or Ag-selenides, sulfides, and sulfosalts hosted in adularia ? quartz ? calcite veins. The intimate association of adularia with these precious metal minerals allows for unambiguous geochronology of the mineralization events. Adularia hosts a variety of precious metal minerals and occurs in these deposits as either thin adularia-only fracture encrustations with electrum as the almost exclusive 83 precious metal mineral or as much wider banded veins that contain multiple generations of adularia + quartz ? calcite along with much higher Se content. The presence of Se has a strong impact on the mineralogy of Ag. In Se-poor deposits Ag is mostly found in the mineral electrum, whereas in Se-rich deposits the Ag-selenide naumannite is the primary Ag-mineral. Multi-element geochemical analysis of samples from the northern Great Basin, and for comparison Colorado and Japan, indicates that nearly all samples contain variable but significant levels of Au, Ag, Pb, As, Sb, Se and Te. The most notable difference that exists between deposits of different regions is the amounts of Au, Ag, Se and Te present. Deposits located in the northern Carlin Trend (Midas and Hollister), National district (National and Buckskin National), War Eagle Mountain, ID, and Koryu, Japan all contain Se-rich ores that are nearly devoid of Te, along with typical Ag/Au ratios of 10 to 1. The deposits of Colorado contain very low amounts of Se, abundant Te, and Au concentrations that are often at least twice that of Ag. The deposits located in the Slumbering Hills (Jumbo, New Alma, Sandman, Sleeper, and Ten Mile) have ore chemistries that are considerably different from any of the other deposits in this study. The Au/Ag ratio is nearly 2 to 1 and all the deposits with the exception of Sleeper contain nearly no Se or Te, as well as having considerably lower levels of base metals. A statistical analysis of just the northern Great Basin deposits indicates that Au shows a strong to moderate statistical correlation with Hg, Sb, Ag, and Mo. A strong correlation also exists between Ag and Se. This may indicate a common source for all the elements. A new system was devised to classify low-sulfidation ores base on elemental ratios. An epithermal trilinear diagram using the metals Au, Ag, and Pb and metalloids 84 As, Sb, Se, and Te indicate that end members in composition exist amongst the low- sulfidation deposits. One end member is represented by the Au-Te ores of the Colorado epithermal deposits and the other end member is represented by the Ag-Se rich ?ginguro- type ores? as seen at Hishikari, Japan and Midas, Nevada. Multiple samples collected at a single deposit generally cluster well together, whereas the assortment in compositions amongst deposits ranges between both end members. If just the deposits of the northern Great Basin are considered, samples plot consistently in the Ag/Au-rich areas of the field and there is considerably more variability in the metalloids field especially related to the Sb+As versus Se levels. The geochronology data generated by this study and others indicate low- sulfidation epithermal mineralization in the northern Great Basin began around 16.5 Ma and continued until at least 15.1 Ma. This study found that in the Slumbering Hills, Nevada area, the earliest mineralization occurred in the Awakening district at Jumbo at 16.53 ? 0.04 Ma and continued within the district until at least 16.03 ? 0.07 Ma at New Alma. To the south of the Slumbering Hills, mineralization occurred at the Ten Mile and Sandman deposits at 16.52 ? 0.04 Ma and 16.17 ? 0.04 Ma respectively. On War Eagle Mountain, Idaho the Oro Fino vein dated at 16.31 ? 0.04 Ma and the area to the southwest (site 3 in this study) was found to be 15.61 ? 0.10 Ma. Jumbo is only slightly younger than the oldest magmatism thought to be associated with the Yellowstone hotspot (16.59 ? 0.10 Ma, Steens Mountain basalt, Brueseke et al., 2007). However, for the region as a whole, no discernable trend presents itself that would suggest deposits get generally younger to the east in line with the track of the Yellowstone hotspot. 85 The data in this study indicate that low-sulfidation epithermal deposits in the northern Great Basin share similar mineralogy, geochemistry, and formed just after early Yellowstone hotspot volcanism. This suggests that the two events are related and that the deposits all share a common source for the majority of ore-mineral constituents. On a broader scale if the deposits of Colorado and Japan are considered, deposits occur in a variety of tectonic settings but share a consistent mineralogy and geochemistry that varies between Se-rich and Te-rich end members. 86 SPECULATIONS AND IMPLICATIONS FOR EXPLORATION A growing body of research suggests that previous genetic models for epithermal precious metal systems, which suggest metals are sourced from host rock leaching or even ambiguous sources, are in need of revision. A compromise of genetic models seems reasonable based on indications that Au and possibly other elements have magmatic sources and that these systems form relatively rapidly. Rather than a strictly crustal or magmatic source for the components in epithermal systems; it appears the epithermal suite elements have a magmatic source, and more common elements that comprise the gangue minerals likely are leached from the local host rocks. This could explain why the mid-Miocene epithermal deposits of the northern Great Basin are relatively similar geochemically, yet have a variety of vein and gangue minerals associated with them. A number of other characteristics of low-sulfidation epithermal deposits can also be proposed. The fact that adularia is present in Se-poor and Se-rich deposits likely indicates that they have separate origins, such as Se is sourced from the mantle, whereas adularia forms when the surrounding host rocks contain enough K and Al to allow it. For the epithermal trilinear diagram, the elements Au, Ag, Se and Te were chosen because they may have a mantle source. The elements As and Sb may have both crustal and mantle sources, and Pb may be mostly leached from local host rocks. By using these 87 elements to evaluate epithermal ores, it may be possible to determine how crustal and mantle contributions influence ore geochemistry. Gold shows a strong to moderate statistical correlation with Hg, Sb, Ag, and Mo, and Ag correlates strongly with Se. This likely indicates the elements all have the same (magmatic?) source. Many of the spatially related deposits discussed above have remarkably consistent geochemistries. Other spatially related deposits such as the National and Buckskin National deposits have a larger degree of geochemical variation between them, thus a wider suite of samples is needed to fully quantify their geochemical differences. However, given that both of these deposits are situated within the National district and are in close proximity, several possibilities could explain their geochemical differences; 1) different pluses of magma carrying different ratios of ore forming elements (i.e. more Pb in the National ores, more Ag in the Buckskin National ores), 2) some type of fractionation occurs on a district-wide scale that results in chemically similar but still unique ores being formed in different deposits, or 3) interaction with local host rocks contribute varying amounts of different elements (i.e. more Sb and As at National, more Se at Buckskin National). One important question with exploration implications is; does epithermal precious metal mineralization associated with the Yellowstone hotspot continue to this day or were the events that created the deposits in the northern Great Basin a unique occurrence? If the Yellowstone hotspot continues to be an ore-forming system then other deposits would be expected along the hotspot?s track. On the other hand, the mantle may have been depleted early on and thus the Yellowstone hotspot did not remain an ore-forming system. 88 The importance of geochronology for exploration cannot be overlooked as well. This type of deposits appears to have only formed in a narrow window of time (ca 16.5- 15 Ma), thus volcanism of this age is has the potential to be a part of an ore-forming system that may not be exposed. Additionally, there is strong geochemical and geochronology evidence that the geologic processes that drove these precious metal epithermal systems were active over relatively large areas and durations of 0.5 Ma or more. This suggests locations such as the Slumbering Hills and the northern Carlin trend remain highly prospective for further exploration. 89 REFERENCES Anders, E., and Grevesse, N., 1989, Abundances of the elements: meteoritic and solar: Geochimica et Cosmochimica Acta, v. 53, p. 197-214. Armstrong, R.L., Taubeneck,W.P., Hales, P.O., 1977, Rb?Sr and K?Ar geochronology of Mesozoic granitic rocks and their Sr isotopic compositions, Oregon, Washington, and Idaho: Geologic Society of America Bulletin, v. 88, p. 397?411. Asher, R.R., 1968, Geology and mineral resources of a portion of the Silver City region, Owhyee County, Idaho: Idaho Bureau of Mines Geology Pamphlet 138, 106 p. Bartlett, M.W., Enders, M.S., and Hruska, D.C., 1991, Geology of the Hollister gold deposit, Ivanhoe district, Elko County, Nevada, in Raines, G.L., Lisle, R.E., Schafer, R.W., and Wilkinson, W.H., eds., Geology and ore deposits of the Great Basin: Geological Society of Nevada Symposium, Reno, 1990, Proceedings, p. 957-978. Bowell, R.J., Hunerlach, M.P., Parshley, J., and Sears, S., 2000, The Ten Mile district, Winnemucca, Nevada: Geology, mineralogy and supergene gold enrichment: Geological Society of Nevada, Geology and Ore Deposits 2000: The Great Basin and Beyond Symposium, May 15-18, 2000, Reno-Sparks, Nevada, Proceedings, p. 349-363. Brueseke, M.E., and Hart, W.K., 2004, The physical and petrologic evolution of a multi- vent volcanic field associated with Yellowstone-Newbery volcanism: Eos, Transactions of AGU, v. 87(47), p. V53A-0605. Brueseke, M.E., Heizler, M.T., Hart, W.K., and Mertzman, S.K., 2007, Distribution of Oregon Plateau (U.S.A.) flood basalt volcanism: The Steens Basalts revisited: Journal of Volcanology, v. 161, p. 187-214. Brueseke, M.E., Hart, W.K., Heizler, M.T., 2007, Chemical and physical diversity of mid-Miocene silicic volcanism in northern Nevada: Bulletin of Volcanology, in press. Brueseke, M.E., Heizler, M.T., Hart, W.K., and Mertzman, S.A., 2007, Distribution and geochronology of Oregon Plateau (U.S.A.) flood basalt volcanism: The Steens Basalt revisited: Journal of Volcanology and Geothermal Research, v. 161, p. 187-214. 90 Bussey, S.D., 1996, Gold mineralization and associated rhyolitic volcanism at the Hog Ranch district, northwest Nevada: Geological Society of Nevada, Geology and Ore deposits of the American Cordillera Symposium, Reno-Sparks, Nevada, April 1995, Proceedings, p. 181-207 Camp, V.E., and Ross, M.E., 2004, Mantle dynamics and genesis of mafic magmatism in the intermontane Pacific Northwest: Journal of Geophysical Research, v. 109, B08204, 14p. Cline, J.S., Hofstra, A.H., Muntean, J.L., Tosdal, R.M., and Hikey, K.A., 2005, Carlin- type gold deposits in Nevada: critical geologic characteristics and viable models: Economic Geology 100th Anniversary Volume, p. 451-484. Connors, K.A., Noble, D.C., Bussey, S.D., and Weiss, S.I., 1993, Initial gold contents of silicic volcanic rocks: Bearing on the behavior of gold in magmatic systems: Geology, v. 21, p. 937-940. Conrad, J.E., and McKee, E.H., 1996, High-precision 40Ar/39Ar ages of rhyolitic host rock and mineralized veins at the Sleeper deposit, Humboldt County, Nevada: Geological Society of Nevada, Geology and Ore Deposits of the American Cordillera Symposium, Reno-Sparks, Nevada, April 1995, Proceedings, p. 257-262 Conrad, J.E. McKee, E.H., Rytuba, J.J., Nash, J.T., and Utterback, W.C., 1993, Geochronology of the Sleeper deposit, Humboldt County, Nevada: Epithermal gold- silver mineralization following emplacement of a silicic flow-dome complex: Economic Geology, v. 88, p. 81-91 Crafford, E.E.J., and Grauch, V.J.S., 2002, Geologic and geophysical evidence for the influence of deep crustal structures on Paleozoic tectonics and the alignment of world- class gold deposits, north-central Nevada, USA: Ore Geology Review, v. 21, p. 157? 184. Cummings, M.L., Evans, J.G., Ferns, M.L., Lees, K.R., 2000. Stratigraphic and structural evolution of the middle Miocene synvolcanic Oregon?Idaho graben: Geology Society of America Bulletin: v. 112, p. 668?682. Dalrymple, G.B., Alexander, E.C., Lanphere, M.A., and Kraker, G.P., 1981, Irradiation of samples for 40Ar/39Ar dating using the Geological Survey TRIGA Reactor: USGS Professional Paper 1176, 55 p. Ekren, E.B., McIntyre, D.H., Bennett, E. H., and Malde, H.E., 1981, Geologic map of Owyhee County, Idaho, west of longitude 116? W, W.S. Geologic Survey Map 1-1256. Fetter, C.W., 2001, Applied Hydrogeology: Prentice-Hall, New Jersey, 374p. 91 Garwin, S., Hall, R., and Watanabe, Y., 2005, Tectonic setting, geology, and gold and copper mineralization in Cenozoic magmatic arcs of southeast Asia and the west Pacific: Economic Geology 100th Anniversary Volume, p. 891-930. Glen, J.M.G., and Ponce, D.A., 2002, Large-scale fractures related to inception of the Yellowstone hotspot: Geology, v. 30, p. 647-650. Goldstrand, P.M., and Schmidt, K.W., 2000, Geology, mineralization, and ore controls at the Ken Snyder gold-silver mine, Elko County, Nevada: Geological Society of Nevada, Geology and Ore Deposits 2000: The Great Basin and Beyond Symposium, May 15-18, 2000, Reno-Sparks, Nevada, Proceedings, p. 265-287 Guilbert, J.M., and Park, C.F., 1985, The geology of ore deposits: W. H. Freeman and Company, New York, 535 p. Halsor, S.P., Bornhorst, T.J., Beebe, M., Richardson, K., and Strowd, W., 1988, Geology of the DeLamar silver mine, Idaho?a volcanic dome complex and genetically associated hydrothermal system: Economic Geology, v. 83, p. 1159-1169. Hart, W.K., and Carlson, R.W., 1985, Distribution and geochronology of Steens Mountain-type basalts from the northwestern Great Basin: Isochron-West, v. 43, p. 5- 10. Hedenquist, J.W., and Lowenstern, J.B., 1994, The role of magmas in the formation of hydrothermal ore deposits: Nature, v. 370, p. 519-527 Heinrich, C.A., 2005, The physical and chemical evolution of low-salinity magmatic fluids at the porphry to epithermal transition; a thermodynamic study: Mineralium Deposita, v. 39, p. 864-889. Heinrich, C.A., 2006, How fast does gold trickle out of volcanoes?: Science, v. 314, p. 263-264. Heinrich, C.A., Driesner, T., Stefansson, A., Seward, T.M., 2004, Magmatic vapor contraction and the transport of gold from the porphyry environment to epithermal ore deposits: Geology, v. 32, p. 761-764. Hollister, V., Hruska, D., and Morre, R., 1992, A mine-exposed host spring deposit and related epithermal gold resource: Economic Geology, v. 87, p. 421-424. Hooper, P.R., 1997, The Columbia River flood basalt provinces; current status, in Mahoney, J.J., and Coffin, M., eds., Large igneous provinces: continental, oceanic, and planetary flood volcanism: Geophysical Monograph, v.100, p.1-27. 92 Hudson, D.M., John, D.A., and Fleck, R.J., 2006, Geologic setting, geochemistry, and geochronology of epithermal gold-silver deposits in the Seven Troughs District, northwest Nevada: Abstracts with Programs - Geological Society of America, v. 37, no. 7, p. 380. Izawa E, Urashima Y, Ibaraki K, Suzuki, R, Yokohama T, Kawasaki K, Koga A, and Taguchi S, 1990, The Hishikari gold deposit: high-grade epithermal veins in Quaternary volcanics of southern Kyushu, Japan: Journal of Geochemical Exploration, v. 36, p. 1-56. John, D.A., Garside, L.J., and Wallace, A.R., 1999, Magmatic and tectonic setting of late Cenozoic epithermal gold-silver deposits in northern Nevada, with an empasis on the Pah Rah and Virginia Ranges and the northern Nevada rift: Geological Society of Nevada Special Publication 29, p. 65-158. John, D.A., Wallace, A.R., Ponce, D.A., Fleck, R., and Conrad, J.E., 2000, New perspectives on the geology and origins of the northern Nevada rift: Geological Society of Nevada, Geology and Ore Deposits 2000: The Great Basin and Beyond Symposium, May 15-18, 2000, Reno-Sparks, Nevada, Proceedings, p. 127-154. John, D.A., 2001, Miocene and early Pliocene epithermal gold-silver deposits in the northern Great Basin, western USA: Characteristics, distribution and relationship to magmatism: Economic Geology, v. 96, p. 1827-1853. John, D.A., Hofstra, A.H., Fleck, R.J., Brummer, J.E., and Saderholm, E.C., 2003, Geologic setting and genesis of the Mule Canyon low-sulfidation epithermal gold-silver deposit, north-central Nevada: Economic Geology, v. 98, p. 425-464. Jordan, B.T., Grunder, A.L., Duncan, R.A., and Deino, A.L., 2004, Geochronology of age-progressive volcanism of the Oregon High Lava Plains: implications for the plume interpretation of Yellowstone: Journal of Geophysical Research, v. 109, B10202., 19 p. Kamenov, G.D., Perfit, M.R., Jonasson, I.R., and Mueller, P.A., 2005, High-precision Pb isotope measurements reveal magma recharge as a mechanism for ore deposit formation: Examples from Lihir Island and Conical seamount, Papau New Guinea: Chemical Geology, v. 219, p. 131-148. Kamenov, G.D., Saunders, J.A., Hames, W.E., and Unger, D.L., Mafic magmas as sources for gold in middle-Miocene epithermal deposits of northern Great Basin, USA: Evidence from Pb isotopic compositions of native gold: Economic Geology, in press. Kistler, R.W., and Peterman, Z.E., 1978, Reconstruction of crustal California on the basis of initial strontium isotopic compositions of Mesozoic granitic rocks: U. S. Geological Survey Professional Paper, v. 107, p. 1-17. 93 Laurettea, D.S., Klaue, B., Blum, J.D., and Buseck, P.R., 2001, Thermal analysis of labile trace elements in CM and CV carbonaceous chondrites using ICP-MS: Lunar and Planetary Science XXXII, n. 1356. Laurettea, D.S., Klaue, B., and Blum, J.D., 2002, Thermal analysis of volatile trace elements of carbonaceous and ordinary chondrites: Lunar and Planetary Science XXXIII, n. 16002. Leavitt, E.D., Spell, T.L., Goldstrand, P.M., and Arehart, G.G., 2004, Geochronology of the Midas low-sulfidation gold-silver deposit, Elko County Nevada: Economic Geology, v. 99, p. 1665-1986. Leeman, W.P., Oldow, J.S., and Hart, W.K., 1992, Lithosphere-scale thrusting in the western U.S. Cordillera as constrained by Sr and Nd isotoic transitions in Neogene volcanic rocks: Geology, v. 20, p. 63-66. Lindgren, W., 1898, Orthoclase as gangue mineral in a fissure vein: American Journal of Science, v. 5, p. 418-420. Lindgren, W., 1900, The gold and silver veins of Silver City, DeLamar, and other mining districts in Idaho: U. S. Geol. Survey 20th Ann. Rept., pt. IIIc, p. 77 - 189. Lindgren, W., 1915, Geology and mineral deposits of the National mining district, Nevada: U. S. Geological Survey Bulletin 601, 58 p. Ludwig, K.R., 2003, User?s manual for Isoplot, v. 3.0, a geochronological tool kit for Microsoft Excel: Berkeley Geochronological Center, Special Publication no. 4. McKee, E.H., and Moring, B.C., 1996, Cenozoic mineral deposits and related rocks: Nevada Bureau of Mines and Geology Open-File Report 96-2, p. 6-1 to 6-8 Muntean, J., Tarnocai, C., Coward, M., Rouby, D., and Jackson, A., 2001, Styles and restorations of Tertiary extension in north-central Nevada: Reno, Geological Society of Nevada Special Publication 33, p. 55-69. Muntean, J.L., Cline, J., Johnston, M.K., Ressel, M.W., Seedorff, E., and Barton, M.D., 2004, Controversies on the origin of world-class gold deposits, part I: Carlin-type gold deposits in Nevada: SEG Newsletter, n. 59, p. 1-17. Nash, J.T., 1972, Fluid inclusion studies of some gold deposits in Nevada: U.S. Geological Survey Professional Paper 800-C, p. C15-C19. Nash, J.T., Utterback, W.C., and Trudel, W.C., 1995, Geology and geochemistry of Tertiary volcanic host rocks, Sleeper gold-silver deposit, Humboldt County, Nevada: U.S. Geological Survey Bulletin 2090, 63 p. 94 Neill, W. M., 1975, Geology of the southeastern Owyhee Mountains and environs, Owyhee County, Idaho: Unpublished M.S. thesis, Stanford University, 111p. Noble, D.C., McCormack, J.K., McKee, E.H., Silberman, M.L., and Wallace, A.B., 1988, Time of mineralization of the evolution of the McDermitt caldera complex, Nevada- Oregon, and the relation of middle Miocene mineralization in the northern Great Basin to coeval regional basaltic magmatic activity: Economic Geology, v. 83, p. 859-863. Pansze, A.J., 1975, Geology and ore deposits of the Silver City-DeLamar-Flint region, Owyhee County, Idaho: Idaho Bureau of Mines Geology Pamphlet 161, 79 p. Peppard, B., 2002, Geology and geochemistry of the Ivanhoe vein system, Elko, Nevada: Unpublished M.S. thesis, Ann Arbor, University of Michigan, 49 p. Peregoedova, A., Barnes,S.J., and Baker, D.R., 2006, An experimental study of mass transfer of platinum-group elements, gold, nickel and copper in sulfur-dominated vapor at magmatic temperature: Chemical Geology, v. 235, p. 59-75. Pierce, K.L., Morgan, L.A., and Saltus, R.W., 2000, The Yellowstone plume head: Postulated tectonic relations to the Vancouver slab, continental boundaries, and climate: U.S. Geological Survey Open-File Report 00-498, 39 p. Ponce, D.A., and Glen, J.M.G., 2002, Relationship of epithermal gold deposits to large- scale fractures in northern Nevada: Economic Geology, v. 97, p. 3-9. Renne, P.R ., Swisher, C.C., Deino, A.L., Karner, D. B., Owens, T. L., and DePaolo, D.J., 1998, Intercalibration of standards, absolute ages, and uncertainties in 40Ar/39Ar dating: Chemical Geology, v. 145, p. 117-152. Roberts, R.J., 1940, Quicksilver deposit at Buckskin Peak National mining district, Humboldt County, Nevada: U.S. Geological Survey Bulletin 922-E, p. 111-133. Rytuba, J.J., and McKee, E. H., 1984, Peralkaline ash-flow tuffs of the McDermitt volcanic field, southeast Oregon and north Entral Nevada: Journal of Geophysical. Research, v. 89, p. 8616-8628. Rytuba, J.J., 1989, Geology of volcanic-hosted Sleeper deposit, Humboldt County, Nevada: Geological Society of America Abstracts with Programs, v. 21, n. 5 p. 138. Sanematsu, K., Watanabe, K., Duncan, R A., and Izawa, E., 2006, The history of vein formation determined by super 40Ar/super 39Ar dating of adularia in the Hosen-1 vein at the Hishikari epithermal gold deposit, Japan: Economic Geology, v. 101, p. 685-698. 95 Saunders, J.A., and Romberger, S.B., 1985, Ore petrology and geochemistry of Tertiary gold telluride deposits of the Colorado mineral belt: Geological Society of America Abstracts and Programs, v. 17, no. 7, p. 707. Saunders, J.A., 1990, Colloidal transport of gold and silica in epithermal precious metal systems: Evidence from the Sleeper deposit, Nevada: Geology, v. 18, p. 757-760. Saunders, J.A., 1994, Silica and gold textures in bonanza ores of the Sleeper Deposit, Humboldt County, Nevada; evidence for colloids and implications for epithermal ore- forming processes: Economic Geology, v. 89, p. 628-638. Saunders, J.A., and Schoenly, P.A., 1995, Boiling, colloid nucleation and aggregation, and the genesis of bonanza Au-Ag ores of the Sleeper deposit, Nevada: Mineralium Deposita, v. 30, p. 199-210. Saunders, J.A., Cook, R.B., and Schoenly, P.A., 1996, Electrum disequilibrium crystallization textures in volcanic-hosted bonanza epithermal gold deposits in northern Nevada: Geological Society of Nevada, Geology and Ore Deposits of the American Cordillera Symposium, Reno-Sparks, Nevada, April 1995, Proceedings, p. 173-179. Sillitoe, R.H., 1989, Gold deposits in western Pacific island arcs; the magmatic connection: Economic Geology Monographs, v. 6, p. 274-291. Sillitoe, R.H., 2002, Some metallogenic featues of gold and copper deposits related to alkaline rocks and consequences for exploration: Mineralium Deposita, v. 37, p. 4-13. Sillitoe, R.H., and Hedenquist, J.W., 2003, Linkages between volcanotectonic settings, ore fluid compositions, and epithermal precious metal deposits: Society of Economic Geologists Special Publication 10, p. 315-343. Simmons, S. F., and Brown, K.L., 2000, Hydrothermal minerals and precious metals in the Broadlands Ohaaki geothermal system: Implicatoins for understanding low- sulfidation epithermal environments: Economic Geology, v. 95, p. 971-999. Simmons, S. F., and Brown, K.L., 2006, Gold in magmatic hydrothermal solutions and the rapid formation of a giant ore deposit: Science, v. 314, no.5797, p. 288-291. Simmons, S.F., and Christenson, B.W., 1994, Origins of calcite in a boiling geothermal system: American Journal of Science, v. 294, p. 361-400. Simmons, S.F., White, N.C., and John, D.A., 2005, Geological characteristics of epithermal precious and base metal deposits: Economic Geology 100th Anniversary Volume, p. 485-522. 96 Teal, L., and Jackson, M., 1997, Geologic Overview of the Carlin Trend gold deposits and descriptions of recent deep discoveries, Vikre, P., Thompson, T.B., Bettles, K., Christensen, O., and Parratt, R., eds., in Carlin-Type Gold Deposits Field Conference: Society of Economic Geologists Guidebook Series, v. 28, p. 3-38. Tewalt, N, A., 1998, Subtle surface expression of high grade veins at the Ivanhoe project: Fall 1998 Field Trip Guidebook, Geological Society of Nevada Special Publication 28, p. 149-161. Thomason, R. E., 1983, Volcanic stratigraphy and epithermal mineralization of the DeLamar silver mine, Owyhee County, Idaho: Unpublished M.S. thesis, Oregon State University, 70 p. Vikre, P.G., 1985, Precious metal vein systems in the National district, Humboldt County, Nevada: Economic Geology, v. 80, p. 360-393. Vikre, P.G., 1987, Paleohydrology of Buckskin Mountain, National district, Humboldt County, Nevada: Economic Geology, v. 82, p. 934-950. Vikre, P.G., 2007, Sinter-vein correlations at Buckskin Mountain, National district, Humboldt County, Nevada: Economic Geology, v. 102, p. 193-224. Wallace, A.R., 2003, Geology of the Ivanhoe Hg-Au district, northern Nevada: Influence of Miocene volcanism, lakes, and active faulting on epithermal mineralization: Economic Geology, v. 98, p. 409-424. Wendt, C.J., 2003, Nevada Mineral Trends: Nevada Bureau of Mines, Open-file report 03-2. Willden, R., 1964, Geology and mineral deposits of Humboldt County, Nevada: Nevada Bureau of Mines and Geology Bulletin 59, 154 p. Winchell, A, N., 1912, Geology of the National district: Mining Scientific Press, Nov. 23. p. 655-658. Winters, J.D., 2001, An introduction to igneous and metamorphic petrology: Prentice Hall, New Jersey, 699 p. Zhang, Z., Mao, J., Fusheng, W., and Pirajno, F., 2006, Native gold and native copper grains enclosed by olivine phenocrysts in a picrite lava of the Emeishan large igneous province, SW China: American Mineralogist, v. 91, p. 1178-1183. Zoback, M.L., and Thompson, G.A., 1978, Basin and Range rifting in northern Nevada: Clues from a mid-Miocene rift and its subsequent offsets: Geology, v. 6, p. 111-116. 97 Zoback, M.L., McKee, E.H., Blakely, R.J., and Thompson, G.A., 1994, The northern Nevada rift: Regional tectono-magmatic relations and middle Miocene stress direction: Geological Society of America Bulletin, v. 106, p. 371-382. 98 APENDICES 99 APENDIX 1 Analytical Facility Description The Auburn Noble Isotope Mas Analysis Laboratory (ANIMAL) was utilized for age determinations in this study: a. This facility is equipped with an ultra-high vacuum, 90-degre sector, 10 cm radius spectrometer optimized for 40 Ar/ 39 Ar research (single-crystal and multigrain sample incremental heating). The spectrometer employs second-order focusing (Cross, 1951), and is fited with a high sensitivity electron-impact source and a single ETP electron multiplier (with signal amplification through a standard pre-amplifier). Analyses of this study were made using a filament current of 2.250 A, and potentials for the source and multiplier of 2000 V and 1250 V, espectively. The total volume of the spectrometer is 400 c. Resolution in the instrument (with fixed slits for the source and detector) is constrained to ~150, and the high sensitivity and low blank of the instrument permits measurement of 10 -14 mole samples to within 0.2% precision. Analyses comprised 10 cycles of measurement over the range of mases and half-mases from m/e=40 to m/e=35.5, and baseline corrected values were extrapolated to the time of inlet, or averaged, depending upon signal evolution. b. The extraction line for this system utilizes a combination of Varian ?mini? and Nupro pneumatic valves, and Varian turbomolecular and ion pumps. Analysis of samples and blanks is fully automated and can be controlled via computer. Pumping of residual and sample reactive gases is acomplished through use of SAES AP-10 non-evaporable geters. Presures in the spectrometer and extraction line, as measured with an ionization gauge, are routinely below ~5x10 -9 torr. A pipete delivers standard aliquots of air for use in measuring sensitivity and mas fractionation. Mas discrimination was typicaly 1.0026?0.0014 per amu (95% confidence level) in November of 2006. c. The extraction line is fited with a 50W Synrad CO2 IR laser for heating and fusing silicate minerals and glases. The sample chamber uses a Cu planchet, KBr cover slips, and low-blank UHV ZnS window (manufactured at Auburn University and based on the design of Cox et al., 2003). In the present configuration, this laser system is suitable for incremental heating and fusion analysis of single crystals and multigrain samples. The laser beam delivery system utilizes movable optical mounts and a fixed sample chamber to further minimize volume and improve conductance of the extraction line. (The time required to inlet, or equilibrate, a ?half-split? of a sample is les than 7 s, and the inlet time for a full sample is ca. 20 s.) Typical blanks for the entire system (4 minute getering time) in November of 2006 are as follows (in moles): 40 Ar, 5.7x10 -17 ; 39 Ar, 1.3x10 -17 ; 38 Ar, 2.8x10 -18 ; 37 Ar, 2.0x10 -18 ; 36 Ar, 1.2x10 -18 . 100 d. Computer control of the laser, laser optics, extraction line, mas spectrometer, and data recording is enabled with National Instruments hardware and the Labview programing environment. Initial data reduction is acomplished through an in- house Excel spreadsheet, with final reduction using Isoplot (Ludwig, 2003). 101 APPENDIX 2 Incremental heating data for the Sandman, New Alma, Jumbo, Ten Mile, and War Eagle Moutain deposits. Sandman deposit step heating increments for 5 single adularia crystals (14-20, 1.2-0.75 mm) of sample: HCN-1 Irradiation filename: au5.1a.adl.ih1 %P 40Ar(*?atm) 39Ar(K) 38Ar(Cl?atm) 37Ar(Ca) 36Ar(Atm) %Rad R Age (Ma) 3.0 3.64E-15 ? 3.38E-18 1.14E-17 ? 4.38E-19 2.5E-18 ? 2.7E-19 -1.5E-18 ? 5.9E-19 1.24E-17 ? 1.48E-19 0% -1.2771 -6.45 ? -90 3.3 1.10E-15 ? 6.15E-18 1.61E-16 ? 1.18E-18 7.5E-19 ? 6.5E-20 5.6E-19 ? 3.9E-19 2.01E-18 ? 8.83E-20 46% 3.1759 15.93 ? 0.88 3.6 1.81E-15 ? 4.98E-18 4.08E-16 ? 9.36E-19 1.1E-18 ? 6.9E-20 -3.0E-19 ? 5.0E-19 1.55E-18 ? 9.60E-20 75% 3.3040 16.57 ? 0.36 4.0 1.65E-15 ? 5.31E-18 4.78E-16 ? 1.45E-18 1.3E-18 ? 5.3E-20 -1.3E-19 ? 4.7E-19 2.91E-19 ? 9.23E-20 95% 3.2630 16.37 ? 0.30 4.3 1.58E-15 ? 4.98E-18 4.64E-16 ? 1.49E-18 1.4E-18 ? 3.8E-20 5.7E-20 ? 5.6E-19 3.35E-19 ? 8.15E-20 94% 3.1987 16.05 ? 0.27 4.5 3.97E-15 ? 4.84E-18 1.17E-15 ? 3.14E-18 2.7E-18 ? 4.7E-20 3.5E-19 ? 4.4E-19 9.35E-19 ? 1.72E-19 93% 3.1654 15.88 ? 0.22 4.8 1.23E-14 ? 1.29E-17 3.39E-15 ? 6.30E-18 8.6E-18 ? 1.4E-19 -3.0E-20 ? 4.6E-19 4.78E-18 ? 1.77E-19 89% 3.2123 16.11 ? 0.09 5.0 1.31E-14 ? 1.07E-17 3.56E-15 ? 5.70E-18 8.9E-18 ? 1.0E-19 -8.9E-19 ? 5.0E-19 5.54E-18 ? 1.80E-19 87% 3.2071 16.09 ? 0.08 5.3 9.43E-15 ? 1.11E-17 2.69E-15 ? 8.12E-18 6.2E-18 ? 7.2E-20 1.3E-19 ? 4.7E-19 2.42E-18 ? 1.64E-19 92% 3.2343 16.22 ? 0.11 5.5 1.02E-14 ? 1.35E-17 2.95E-15 ? 8.41E-18 6.1E-18 ? 7.8E-20 9.7E-20 ? 4.4E-19 2.59E-18 ? 9.99E-20 93% 3.2121 16.11 ? 0.07 5.8 1.56E-14 ? 1.50E-17 4.61E-15 ? 9.84E-18 1.0E-17 ? 7.5E-20 -1.1E-18 ? 5.8E-19 2.19E-18 ? 1.00E-19 96% 3.2352 16.23 ? 0.05 6.0 5.39E-16 ? 2.84E-18 1.58E-16 ? 1.03E-18 2.9E-19 ? 3.4E-20 -7.5E-19 ? 4.0E-19 4.43E-20 ? 6.96E-20 98% 3.3345 16.72 ? 0.67 6.5 6.30E-16 ? 3.20E-18 1.82E-16 ? 1.10E-18 4.4E-19 ? 4.3E-20 -6.5E-19 ? 3.6E-19 3.70E-20 ? 7.92E-20 98% 3.3938 17.02 ? 0.66 7.0 2.76E-16 ? 3.07E-18 7.99E-17 ? 7.49E-19 1.7E-19 ? 4.0E-20 2.5E-20 ? 4.2E-19 7.48E-20 ? 7.36E-20 92% 3.1721 15.91 ? 1.39 8.0 1.89E-16 ? 3.02E-18 5.58E-17 ? 7.17E-19 -5.2E-20 ? -2.4E-20 -1.1E-18 ? 4.3E-19 3.96E-20 ? 6.37E-20 94% 3.1826 15.97 ? 1.73 9.0 1.90E-16 ? 3.18E-18 5.48E-17 ? 5.27E-19 -3.5E-19 ? -4.0E-19 -4.6E-19 ? 3.7E-19 4.70E-20 ? 6.96E-20 93% 3.2073 16.09 ? 1.91 10.0 3.37E-17 ? 2.03E-18 8.76E-18 ? 3.62E-19 -5.3E-19 ? -2.2E-19 -5.5E-20 ? 3.3E-19 2.64E-20 ? 8.13E-20 77% 2.9501 14.80 ? 13 11.0 1.13E-17 ? 2.12E-18 2.88E-18 ? 3.86E-19 -3.6E-19 ? -2.1E-19 9.5E-20 ? 4.6E-19 -2.35E-19 ? -1.17E-19 715% 28.0900 136.26 ? 60 12.0 1.27E-17 ? 2.25E-18 2.37E-18 ? 3.75E-19 -4.9E-19 ? -1.9E-19 -3.5E-19 ? 4.2E-19 -1.43E-19 ? -1.33E-19 432% 23.0992 112.79 ? 82 14.0 1.83E-16 ? 2.34E-18 1.57E-18 ? 3.48E-19 -2.1E-19 ? -2.0E-19 5.7E-19 ? 4.1E-19 5.35E-19 ? 8.63E-20 13% 15.6469 77.17 ? 186 Note: %P = percentage of total laser output (60 w). 102 Irradiation filename: au5.1a.adl.ih2 %P 40Ar(*?atm) 39Ar(K) 38Ar(Cl?atm) 37Ar(Ca) 36Ar(Atm) %Rad R Age (Ma) 3.0 1.07E-15 ? 3.91E-18 4.63E-18 ? 4.01E-19 7.6E-19 ? 1.6E-19 2.5E-19 ? 3.4E-19 3.85E-18 ? 1.21E-19 -7% -14.9832 -77.12 ? -154 3.3 1.12E-15 ? 3.86E-18 1.23E-16 ? 8.68E-19 8.8E-19 ? 8.6E-20 1.0E-19 ? 5.3E-19 2.84E-18 ? 1.25E-19 25% 2.2698 11.40 ? 1.57 3.6 1.44E-15 ? 3.49E-18 4.08E-16 ? 1.50E-18 1.2E-18 ? 5.0E-20 9.0E-19 ? 5.2E-19 8.11E-19 ? 1.19E-19 83% 2.9324 14.72 ? 0.44 4.0 1.50E-15 ? 6.75E-18 4.49E-16 ? 1.58E-18 1.4E-18 ? 5.0E-20 2.5E-19 ? 3.1E-19 1.46E-19 ? 1.40E-19 97% 3.2366 16.24 ? 0.47 4.3 8.09E-15 ? 6.48E-18 2.34E-15 ? 3.28E-18 6.6E-18 ? 1.1E-19 7.3E-19 ? 4.0E-19 2.01E-18 ? 1.62E-19 93% 3.2042 16.07 ? 0.11 4.5 1.50E-14 ? 1.63E-17 4.11E-15 ? 6.46E-18 1.0E-17 ? 1.1E-19 -1.7E-19 ? 4.4E-19 6.47E-18 ? 1.81E-19 87% 3.1853 15.98 ? 0.07 4.8 7.89E-15 ? 5.62E-18 2.30E-15 ? 4.91E-18 5.8E-18 ? 9.1E-20 1.0E-19 ? 4.2E-19 2.03E-18 ? 1.33E-19 92% 3.1603 15.85 ? 0.09 5.0 8.07E-15 ? 9.30E-18 2.33E-15 ? 3.52E-18 5.6E-18 ? 1.3E-19 1.4E-19 ? 4.4E-19 2.08E-18 ? 1.32E-19 92% 3.1983 16.04 ? 0.09 5.3 2.14E-15 ? 5.15E-18 6.17E-16 ? 1.50E-18 1.9E-18 ? 5.3E-20 2.7E-19 ? 3.7E-19 5.26E-19 ? 1.87E-19 93% 3.2121 16.11 ? 0.45 5.5 4.94E-16 ? 4.67E-18 1.43E-16 ? 7.53E-19 4.4E-20 ? 6.9E-21 3.0E-19 ? 3.9E-19 1.53E-19 ? 7.16E-20 91% 3.1469 15.79 ? 0.77 5.8 3.35E-16 ? 3.89E-18 9.69E-17 ? 1.19E-18 2.0E-19 ? 3.1E-20 1.9E-19 ? 4.4E-19 5.16E-20 ? 8.12E-20 95% 3.2972 16.54 ? 1.28 6.0 6.76E-17 ? 2.53E-18 1.78E-17 ? 4.14E-19 1.1E-19 ? 6.9E-20 -2.0E-19 ? 4.7E-19 3.92E-20 ? 7.57E-20 83% 3.1358 15.73 ? 6.35 6.5 2.09E-17 ? 2.73E-18 2.08E-18 ? 3.00E-19 -1.0E-21 ? -8.7E-21 -2.5E-19 ? 3.7E-19 -2.77E-19 ? -1.48E-19 492% 49.3967 233.17 ? 103.3 7.0 3.28E-17 ? 2.92E-18 3.61E-18 ? 2.53E-19 -7.4E-20 ? -3.8E-19 1.7E-19 ? 4.4E-19 2.54E-20 ? 7.50E-20 77% 7.0108 34.99 ? 31.09 8.0 2.12E-17 ? 2.36E-18 2.50E-18 ? 3.38E-19 2.4E-19 ? 1.3E-19 -1.6E-19 ? 4.1E-19 3.80E-20 ? 7.46E-20 47% 3.9613 19.85 ? 44.85 9.0 7.15E-19 ? 1.51E-18 1.07E-19 ? 2.99E-19 -2.0E-19 ? -2.2E-19 7.9E-19 ? 4.4E-19 5.00E-20 ? 6.86E-20 -1966% -131.7752 -827.99 ? -2712. 10.0 2.17E-18 ? 2.24E-18 6.34E-19 ? 3.35E-19 -1.7E-19 ? -1.9E-19 -7.8E-20 ? 5.0E-19 -7.15E-20 ? -7.36E-20 1074% 36.7539 176.30 ? 185.9 11.0 1.15E-19 ? 1.94E-18 -9.15E-19 ? -4.02E-19 -2.9E-19 ? -1.9E-19 2.3E-19 ? 3.5E-19 -2.91E-19 ? -1.25E-19 74925% -94.2096 -550.87 ? -337 12.0 1.33E-17 ? 1.83E-18 6.26E-19 ? 3.16E-19 -2.6E-19 ? -1.9E-19 5.8E-19 ? 4.9E-19 -8.17E-20 ? -6.85E-20 282% 59.8454 278.85 ? 183 14.0 2.98E-16 ? 2.65E-18 5.29E-19 ? 3.19E-19 -1.7E-19 ? -1.9E-19 2.9E-19 ? 4.7E-19 8.64E-19 ? 8.17E-20 14% 79.8724 363.30 ? 2041 103 Irradiation filename: au5.1a.adl.ih3 %P 40Ar(*?atm) 39Ar(K) 38Ar(Cl?atm) 37Ar(Ca) 36Ar(Atm) %Rad R Age (Ma) 3.0 1.58E-15 ? 4.96E-18 2.17E-18 ? 4.14E-19 7.6E-19 ? 2.3E-19 2.4E-19 ? 4.4E-19 5.26E-18 ? 1.30E-19 2% 11.2053 55.60 ? 9 3.3 9.66E-16 ? 4.29E-18 1.66E-17 ? 4.22E-19 7.3E-19 ? 1.5E-19 -5.0E-21 ? 4.3E-19 3.04E-18 ? 8.48E-20 7% 4.0022 20.05 ? 12 3.6 1.93E-15 ? 6.71E-18 2.86E-16 ? 1.23E-18 1.2E-18 ? 6.5E-20 2.6E-19 ? 5.5E-19 2.79E-18 ? 2.13E-19 57% 3.8886 19.49 ? 1.12 4.0 1.98E-15 ? 5.23E-18 3.92E-16 ? 1.97E-18 1.3E-18 ? 5.5E-20 1.5E-19 ? 4.6E-19 2.24E-18 ? 7.73E-20 67% 3.3681 16.89 ? 0.33 4.3 4.89E-16 ? 4.32E-18 1.14E-16 ? 5.03E-19 2.5E-19 ? 3.8E-20 8.7E-19 ? 4.8E-19 4.78E-19 ? 8.72E-20 71% 3.0387 15.25 ? 1.15 4.5 1.31E-15 ? 5.09E-18 3.04E-16 ? 8.22E-19 1.1E-18 ? 5.4E-20 7.5E-19 ? 4.4E-19 1.48E-18 ? 1.37E-19 67% 2.8536 14.32 ? 0.68 4.8 2.89E-15 ? 3.96E-18 7.88E-16 ? 2.74E-18 2.3E-18 ? 5.5E-20 -3.6E-19 ? 4.1E-19 1.54E-18 ? 1.25E-19 84% 3.0817 15.46 ? 0.24 5.0 3.25E-15 ? 2.81E-18 9.26E-16 ? 2.21E-18 2.1E-18 ? 7.3E-20 -7.3E-20 ? 4.7E-19 1.27E-18 ? 1.32E-19 88% 3.0999 15.55 ? 0.22 5.3 8.95E-15 ? 1.02E-17 2.42E-15 ? 7.17E-18 6.7E-18 ? 5.1E-20 -2.4E-19 ? 5.1E-19 4.29E-18 ? 1.51E-19 86% 3.1760 15.93 ? 0.11 5.5 2.15E-14 ? 1.58E-17 5.77E-15 ? 9.92E-18 1.7E-17 ? 1.6E-19 -4.2E-19 ? 5.2E-19 9.70E-18 ? 1.74E-19 87% 3.2252 16.18 ? 0.06 5.8 7.20E-15 ? 5.77E-18 2.07E-15 ? 4.60E-18 5.3E-18 ? 1.0E-19 7.1E-20 ? 4.9E-19 1.66E-18 ? 8.88E-20 93% 3.2346 16.23 ? 0.08 6.0 1.25E-15 ? 4.30E-18 3.56E-16 ? 1.84E-18 1.4E-18 ? 6.0E-20 -2.7E-19 ? 4.4E-19 3.12E-19 ? 1.01E-19 93% 3.2592 16.35 ? 0.43 6.5 2.49E-15 ? 8.55E-18 7.13E-16 ? 2.49E-18 1.6E-18 ? 5.1E-20 1.2E-19 ? 5.9E-19 7.41E-19 ? 8.49E-20 91% 3.1892 16.00 ? 0.20 7.0 4.35E-17 ? 1.66E-18 1.17E-17 ? 3.59E-19 1.4E-19 ? 1.1E-19 -4.0E-19 ? 5.1E-19 8.78E-20 ? 9.20E-20 40% 1.4982 7.53 ? 11 8.0 2.01E-17 ? 1.79E-18 9.40E-18 ? 3.27E-19 -2.5E-19 ? -3.4E-19 -1.6E-19 ? 5.1E-19 -6.71E-20 ? -7.99E-20 199% 4.2490 21.28 ? 12 9.0 5.99E-18 ? 2.05E-18 1.48E-18 ? 2.91E-19 1.4E-19 ? 2.0E-19 4.8E-20 ? 4.9E-19 8.40E-20 ? 7.76E-20 -314% -12.7128 -65.22 ? -81 10.0 2.98E-18 ? 1.55E-18 1.16E-18 ? 3.70E-19 -6.8E-20 ? -2.3E-19 4.0E-19 ? 4.7E-19 1.11E-19 ? 8.86E-20 -998% -25.6109 -133.90 ? -127 104 Irradiation filename: au5.1a.adl.ih4 %P 40Ar(*?atm) 39Ar(K) 38Ar(Cl?atm) 37Ar(Ca) 36Ar(Atm) %Rad R Age (Ma) 3.0 6.66E-16 ? 4.41E-18 7.80E-19 ? 3.32E-19 1.4E-19 ? 1.7E-19 2.5E-19 ? 4.7E-19 2.06E-18 ? 2.05E-19 9% 74.4690 340.90 ? 2285 3.3 2.50E-16 ? 3.00E-18 1.25E-17 ? 4.56E-19 -7.6E-20 ? -3.3E-19 1.0E-19 ? 5.4E-19 1.01E-18 ? 8.37E-20 -19% -3.7349 -18.92 ? -12 3.6 2.48E-16 ? 1.93E-18 4.51E-17 ? 5.07E-19 -2.5E-19 ? -2.5E-19 -2.9E-21 ? 4.7E-19 3.88E-19 ? 8.69E-20 54% 2.9538 14.82 ? 2.89 4.0 1.08E-15 ? 2.21E-18 3.17E-16 ? 1.18E-18 4.3E-19 ? 2.4E-20 9.1E-20 ? 3.6E-19 1.42E-19 ? 7.85E-20 96% 3.2550 16.33 ? 0.37 4.3 5.75E-16 ? 3.67E-18 1.76E-16 ? 1.57E-18 9.0E-19 ? 8.5E-20 -2.6E-20 ? 4.6E-19 -5.81E-20 ? -1.17E-19 103% 3.3699 16.90 ? 1.00 4.5 7.77E-16 ? 3.78E-18 2.38E-16 ? 1.49E-18 3.9E-19 ? 2.6E-20 -5.0E-19 ? 6.1E-19 4.98E-20 ? 1.92E-19 98% 3.2070 16.09 ? 1.20 4.8 1.43E-15 ? 4.25E-18 4.30E-16 ? 1.01E-18 8.3E-19 ? 5.5E-20 -4.5E-19 ? 4.4E-19 1.71E-19 ? 1.46E-19 96% 3.1946 16.03 ? 0.51 5.0 4.64E-15 ? 6.10E-18 1.39E-15 ? 2.12E-18 2.3E-18 ? 4.7E-20 -3.2E-19 ? 4.5E-19 4.97E-19 ? 1.39E-19 97% 3.2236 16.17 ? 0.15 5.3 1.14E-14 ? 8.80E-18 3.36E-15 ? 1.26E-17 7.0E-18 ? 5.2E-20 2.3E-19 ? 4.5E-19 1.70E-18 ? 1.78E-19 96% 3.2276 16.19 ? 0.10 5.5 1.17E-14 ? 8.80E-18 3.52E-15 ? 7.00E-18 7.7E-18 ? 7.4E-20 2.3E-19 ? 3.8E-19 1.62E-18 ? 9.51E-20 96% 3.1906 16.01 ? 0.05 5.8 1.17E-15 ? 5.35E-18 3.51E-16 ? 8.28E-19 7.0E-19 ? 3.8E-20 -6.6E-20 ? 4.2E-19 1.70E-19 ? 8.32E-20 96% 3.2009 16.06 ? 0.36 6.0 3.64E-16 ? 2.11E-18 1.05E-16 ? 9.21E-19 3.9E-19 ? 6.5E-20 1.7E-19 ? 3.4E-19 -5.42E-20 ? -8.43E-20 104% 3.6244 18.17 ? 1.21 6.5 7.57E-18 ? 2.12E-18 1.50E-18 ? 4.70E-19 4.1E-19 ? 1.8E-19 -3.5E-19 ? 4.2E-19 -8.96E-20 ? -9.11E-20 450% 22.7664 111.22 ? 92 7.0 2.72E-17 ? 2.58E-18 6.74E-18 ? 4.21E-19 6.1E-20 ? 1.0E-19 -3.4E-19 ? 3.9E-19 -1.29E-19 ? -9.06E-20 240% 9.6663 48.06 ? 19 8.0 7.49E-18 ? 2.08E-18 7.54E-19 ? 3.71E-19 2.4E-19 ? 1.9E-19 1.8E-19 ? 4.0E-19 -4.52E-20 ? -8.42E-20 279% 27.6782 134.34 ? 167 9.0 7.24E-18 ? 1.90E-18 1.80E-18 ? 4.92E-19 1.6E-19 ? 1.9E-19 -3.2E-19 ? 3.5E-19 -1.17E-19 ? -8.53E-20 578% 23.2122 113.33 ? 73 10.0 9.97E-18 ? 2.29E-18 -3.40E-19 ? -4.38E-19 -6.7E-21 ? -1.3E-19 -4.0E-19 ? 3.8E-19 -3.44E-19 ? -1.42E-19 1121% -329.1044 -4538.78 ? -5618 105 Irradiation filename: au5.1a.adl.ih5 %P 40Ar(*?atm) 39Ar(K) 38Ar(Cl?atm) 37Ar(Ca) 36Ar(Atm) %Rad R Age (Ma) 3.0 1.16E-15 ? 3.57E-18 4.26E-18 ? 3.49E-19 7.7E-19 ? 2.1E-19 -8.3E-19 ? 3.8E-19 4.07E-18 ? 1.51E-19 -3% -9.4739 -48.38 ? -173 3.3 4.26E-16 ? 3.41E-18 8.81E-17 ? 8.09E-19 4.3E-19 ? 5.5E-20 5.1E-21 ? 4.8E-19 5.74E-19 ? 1.50E-19 60% 2.9068 14.59 ? 2.54 3.6 6.43E-16 ? 4.31E-18 1.65E-16 ? 8.15E-19 1.7E-19 ? 1.9E-20 1.6E-19 ? 4.9E-19 3.91E-19 ? 1.49E-19 82% 3.1958 16.03 ? 1.35 4.0 3.21E-15 ? 6.72E-18 9.35E-16 ? 3.31E-18 1.8E-18 ? 5.0E-20 -5.1E-19 ? 4.3E-19 6.90E-19 ? 1.42E-19 94% 3.2185 16.15 ? 0.24 4.3 8.16E-15 ? 6.66E-18 2.34E-15 ? 4.74E-18 5.9E-18 ? 1.2E-19 -1.3E-18 ? 5.7E-19 2.25E-18 ? 1.61E-19 92% 3.2007 16.06 ? 0.11 4.5 2.02E-14 ? 2.01E-17 6.02E-15 ? 1.01E-17 1.5E-17 ? 1.2E-19 4.1E-19 ? 4.2E-19 2.65E-18 ? 1.11E-19 96% 3.2254 16.18 ? 0.04 4.8 3.55E-15 ? 4.17E-18 1.08E-15 ? 4.72E-18 2.1E-18 ? 4.4E-20 -2.5E-19 ? 3.9E-19 3.49E-19 ? 8.42E-20 97% 3.1935 16.02 ? 0.14 5.0 4.10E-16 ? 2.89E-18 1.21E-16 ? 1.05E-18 -8.1E-20 ? -1.7E-20 5.3E-19 ? 3.5E-19 -1.69E-19 ? -1.12E-19 112% 3.7820 18.96 ? 1.38 5.3 1.83E-16 ? 2.76E-18 5.44E-17 ? 7.19E-19 -4.1E-19 ? -6.2E-19 1.7E-19 ? 3.3E-19 -1.38E-19 ? -1.17E-19 122% 4.1078 20.58 ? 3.21 5.5 8.98E-17 ? 1.99E-18 2.69E-17 ? 5.03E-19 -7.5E-20 ? -8.3E-20 1.3E-19 ? 3.4E-19 -7.54E-20 ? -7.73E-20 125% 4.1659 20.87 ? 4.28 5.8 2.40E-17 ? 2.04E-18 6.69E-18 ? 3.47E-19 -2.0E-19 ? -3.1E-19 3.2E-19 ? 4.0E-19 -2.56E-19 ? -1.38E-19 416% 14.9177 73.64 ? 30.38 6.0 8.97E-17 ? 2.66E-18 2.41E-17 ? 3.53E-19 4.3E-20 ? 2.4E-20 -4.1E-19 ? 3.8E-19 -3.22E-20 ? -8.67E-20 111% 4.1162 20.62 ? 5.36 6.5 3.93E-17 ? 2.51E-18 1.01E-17 ? 3.89E-19 -5.1E-20 ? -2.4E-19 -5.4E-19 ? 2.7E-19 -3.45E-19 ? -1.08E-19 359% 14.0192 69.29 ? 15 7.0 1.84E-17 ? 2.11E-18 5.09E-18 ? 2.49E-19 4.7E-20 ? 7.7E-20 -2.2E-19 ? 4.2E-19 -5.61E-22 ? -8.28E-20 101% 3.6509 18.30 ? 24 8.0 1.12E-17 ? 1.71E-18 1.28E-18 ? 3.01E-19 -6.6E-20 ? -2.0E-19 -3.4E-19 ? 2.8E-19 -3.74E-19 ? -1.45E-19 1082% 95.1714 425.26 ? 175 9.0 8.19E-18 ? 2.46E-18 1.03E-18 ? 3.87E-19 -3.2E-19 ? -1.8E-19 -9.4E-19 ? 2.5E-19 -4.46E-20 ? -7.88E-20 261% 20.8243 101.99 ? 115 106 New Alma deposit step heating increments for 5 single adularia crystals (14-20 mesh size, 1.2-0.75 mm) of sample: HCN-2 Irradiation filename: au5.1c.adl.ih1 %P 40Ar(*?atm) 39Ar(K) 38Ar(Cl?atm) 37Ar(Ca) 36Ar(Atm) %Rad R Age (Ma) 3.0 3.28E-16 ? 3.00E-18 1.12E-17 ? 5.82E-19 7.1E-20 ? 8.3E-20 1.4E-19 ? 5.3E-19 8.79E-19 ? 9.08E-20 21% 6.0812 30.38 ? 15 3.3 4.65E-16 ? 3.23E-18 9.45E-17 ? 4.94E-19 -1.1E-19 ? -2.8E-20 9.5E-20 ? 5.0E-19 3.27E-19 ? 8.60E-20 79% 3.8939 19.52 ? 1.37 3.6 5.85E-16 ? 2.78E-18 1.78E-16 ? 1.13E-18 3.4E-19 ? 4.0E-20 2.6E-19 ? 5.3E-19 -1.67E-19 ? -7.80E-20 108% 3.5533 17.82 ? 0.66 4.0 2.99E-15 ? 3.57E-18 8.02E-16 ? 2.62E-18 1.6E-18 ? 4.6E-20 5.7E-20 ? 5.2E-19 1.38E-18 ? 9.96E-20 86% 3.2184 16.14 ? 0.20 4.3 1.84E-15 ? 4.82E-18 5.64E-16 ? 1.92E-18 1.5E-18 ? 6.6E-20 -3.6E-19 ? 5.0E-19 1.01E-19 ? 8.17E-20 98% 3.2020 16.06 ? 0.23 4.5 1.60E-15 ? 4.23E-18 4.91E-16 ? 1.29E-18 7.4E-19 ? 2.5E-20 3.0E-19 ? 4.7E-19 2.33E-20 ? 1.88E-19 100% 3.2437 16.27 ? 0.57 4.8 6.14E-15 ? 3.72E-18 1.91E-15 ? 4.17E-18 4.7E-18 ? 9.6E-20 1.7E-19 ? 4.6E-19 4.05E-19 ? 1.54E-19 98% 3.1588 15.85 ? 0.13 5.0 4.97E-15 ? 4.31E-18 1.56E-15 ? 2.86E-18 3.6E-18 ? 6.2E-20 8.8E-20 ? 5.2E-19 3.40E-19 ? 1.64E-19 98% 3.1290 15.70 ? 0.16 5.3 4.73E-15 ? 4.89E-18 1.49E-15 ? 7.61E-18 2.8E-18 ? 4.8E-20 -1.6E-19 ? 4.5E-19 3.42E-19 ? 1.59E-19 98% 3.1021 15.56 ? 0.18 5.5 1.41E-14 ? 8.95E-18 4.40E-15 ? 6.11E-18 9.7E-18 ? 9.1E-20 1.4E-18 ? 4.4E-19 4.81E-19 ? 1.54E-19 99% 3.1627 15.87 ? 0.06 5.8 4.24E-15 ? 3.65E-18 1.32E-15 ? 3.00E-18 3.1E-18 ? 5.4E-20 5.1E-19 ? 4.8E-19 1.08E-19 ? 9.18E-20 99% 3.1740 15.92 ? 0.11 6.0 2.45E-15 ? 5.37E-18 7.60E-16 ? 1.87E-18 1.9E-18 ? 3.6E-20 -3.3E-20 ? 2.9E-19 1.89E-19 ? 1.45E-19 98% 3.1424 15.76 ? 0.29 6.5 1.73E-15 ? 5.44E-18 5.29E-16 ? 1.51E-18 1.5E-18 ? 7.3E-20 3.8E-19 ? 3.6E-19 2.80E-19 ? 1.43E-19 95% 3.1097 15.60 ? 0.41 7.0 1.09E-16 ? 2.13E-18 3.29E-17 ? 5.16E-19 -1.6E-19 ? -1.7E-19 -2.3E-19 ? 3.7E-19 3.61E-19 ? 1.39E-19 2% 0.0806 0.41 ? 6.33 8.0 1.86E-16 ? 2.45E-18 5.69E-17 ? 6.94E-19 1.1E-19 ? 4.3E-20 3.4E-20 ? 3.4E-19 2.12E-19 ? 1.43E-19 66% 2.1607 10.86 ? 3.74 9.0 2.00E-17 ? 2.07E-18 5.28E-18 ? 6.39E-19 -1.8E-19 ? -2.1E-19 1.7E-18 ? 5.7E-19 2.57E-19 ? 1.37E-19 -280% -10.6002 -54.22 ? -40 107 Irradiation filename: au5.1c.adl.ih2 %P 40Ar(*?atm) 39Ar(K) 38Ar(Cl?atm) 37Ar(Ca) 36Ar(Atm) %Rad R Age (Ma) 3.0 3.05E-16 ? 2.56E-18 3.48E-18 ? 3.62E-19 4.2E-19 ? 1.7E-19 2.1E-19 ? 5.5E-19 1.02E-18 ? 9.37E-20 1% 0.9187 4.62 ? 76 3.3 2.67E-16 ? 2.73E-18 3.80E-17 ? 5.13E-19 6.2E-19 ? 1.3E-19 -2.9E-19 ? 4.6E-19 3.81E-19 ? 7.78E-20 58% 4.0590 20.34 ? 3.09 3.6 6.61E-16 ? 3.70E-18 1.61E-16 ? 1.07E-18 1.1E-18 ? 7.5E-20 4.9E-19 ? 4.6E-19 7.59E-20 ? 1.38E-19 97% 3.9583 19.84 ? 1.28 4.0 2.15E-15 ? 5.38E-18 6.43E-16 ? 1.80E-18 1.5E-18 ? 4.3E-20 2.7E-19 ? 5.0E-19 2.23E-19 ? 9.79E-20 97% 3.2444 16.27 ? 0.23 4.3 1.05E-15 ? 5.51E-18 3.21E-16 ? 1.69E-18 9.6E-19 ? 5.2E-20 4.3E-19 ? 4.2E-19 2.06E-20 ? 8.58E-20 99% 3.2363 16.23 ? 0.41 4.5 1.12E-16 ? 2.09E-18 3.32E-17 ? 4.75E-19 3.9E-19 ? 1.2E-19 -4.2E-19 ? 4.7E-19 -3.14E-19 ? -1.36E-19 183% 6.1637 30.79 ? 6.05 4.8 6.32E-16 ? 2.87E-18 1.94E-16 ? 7.52E-19 4.9E-19 ? 5.3E-20 -3.9E-19 ? 4.8E-19 1.17E-19 ? 7.82E-20 95% 3.0715 15.41 ? 0.60 5.0 8.05E-16 ? 5.01E-18 2.53E-16 ? 1.54E-18 9.1E-19 ? 5.7E-20 -4.3E-19 ? 4.4E-19 -5.11E-20 ? -9.00E-20 102% 3.2311 16.21 ? 0.54 5.3 1.42E-15 ? 5.39E-18 4.37E-16 ? 1.11E-18 1.3E-18 ? 6.0E-20 3.4E-19 ? 5.5E-19 2.15E-19 ? 8.79E-20 96% 3.0960 15.53 ? 0.31 5.5 2.31E-15 ? 5.40E-18 7.15E-16 ? 2.36E-18 1.9E-18 ? 6.6E-20 -4.7E-19 ? 5.1E-19 7.60E-20 ? 8.93E-20 99% 3.1918 16.01 ? 0.20 5.8 4.69E-15 ? 8.01E-18 1.45E-15 ? 3.51E-18 3.5E-18 ? 5.2E-20 -4.0E-19 ? 3.6E-19 1.39E-19 ? 8.58E-20 99% 3.1963 16.03 ? 0.10 6.0 6.70E-15 ? 4.16E-18 2.07E-15 ? 3.35E-18 4.2E-18 ? 5.8E-20 -2.6E-19 ? 4.5E-19 2.50E-19 ? 7.79E-20 99% 3.1948 16.03 ? 0.06 6.5 1.72E-14 ? 1.94E-17 5.31E-15 ? 6.74E-18 1.2E-17 ? 1.3E-19 2.6E-19 ? 5.5E-19 4.18E-19 ? 8.48E-20 99% 3.2065 16.09 ? 0.04 7.0 1.56E-14 ? 1.10E-17 4.85E-15 ? 9.08E-18 1.2E-17 ? 6.5E-20 -4.4E-19 ? 5.0E-19 5.03E-19 ? 7.83E-20 99% 3.1806 15.96 ? 0.04 8.0 1.12E-14 ? 9.60E-18 3.50E-15 ? 3.97E-18 7.9E-18 ? 1.0E-19 3.2E-19 ? 4.8E-19 1.58E-21 ? 1.13E-19 100% 3.2101 16.10 ? 0.05 9.0 1.55E-15 ? 4.91E-18 4.81E-16 ? 1.51E-18 9.1E-19 ? 3.0E-20 4.4E-19 ? 5.1E-19 2.13E-19 ? 8.15E-20 96% 3.0990 15.55 ? 0.26 108 Irradiation filename: au5.1c.adl.ih3 %P 40Ar(*?atm) 39Ar(K) 38Ar(Cl?atm) 37Ar(Ca) 36Ar(Atm) %Rad R Age (Ma) 3.0 6.37E-17 ? 1.87E-18 2.57E-18 ? 2.85E-19 -7.1E-20 ? -4.5E-19 -5.1E-19 ? 3.9E-19 1.56E-19 ? 9.05E-20 28% 6.8747 34.31 ? 54 3.3 9.80E-17 ? 2.41E-18 1.30E-17 ? 4.35E-19 -6.4E-20 ? -2.7E-19 -5.0E-19 ? 4.2E-19 1.40E-19 ? 8.19E-20 58% 4.3335 21.70 ? 9.44 3.6 8.52E-16 ? 3.66E-18 2.18E-16 ? 7.00E-19 5.9E-19 ? 5.9E-20 -5.1E-19 ? 3.0E-19 -2.27E-20 ? -1.56E-19 101% 3.9294 19.69 ? 1.07 4.0 2.02E-15 ? 3.81E-18 6.16E-16 ? 2.26E-18 1.6E-18 ? 6.3E-20 -5.2E-19 ? 3.6E-19 9.88E-20 ? 8.28E-20 99% 3.2252 16.18 ? 0.21 4.3 2.80E-15 ? 3.69E-18 8.75E-16 ? 3.19E-18 2.2E-18 ? 7.9E-20 -6.9E-19 ? 3.5E-19 3.28E-20 ? 7.30E-20 100% 3.1895 16.00 ? 0.14 4.5 5.17E-15 ? 5.20E-18 1.62E-15 ? 4.87E-18 3.7E-18 ? 7.0E-20 3.4E-19 ? 4.3E-19 1.15E-19 ? 8.91E-20 99% 3.1662 15.88 ? 0.10 4.8 1.32E-14 ? 1.59E-17 4.09E-15 ? 5.67E-18 1.1E-17 ? 6.0E-20 3.1E-19 ? 4.3E-19 2.29E-19 ? 8.82E-20 99% 3.2093 16.10 ? 0.04 5.0 9.16E-15 ? 5.47E-18 2.84E-15 ? 4.02E-18 6.9E-18 ? 6.7E-20 -1.3E-19 ? 3.6E-19 2.87E-19 ? 7.51E-20 99% 3.1944 16.03 ? 0.05 5.3 7.33E-15 ? 7.03E-18 2.29E-15 ? 5.71E-18 5.1E-18 ? 8.2E-20 6.4E-20 ? 3.3E-19 -5.07E-20 ? -7.93E-20 100% 3.2079 16.09 ? 0.07 5.5 1.99E-15 ? 5.36E-18 6.22E-16 ? 3.68E-18 1.2E-18 ? 5.0E-20 1.6E-20 ? 3.9E-19 -4.60E-19 ? -1.39E-19 107% 3.4109 17.11 ? 0.35 5.8 2.68E-16 ? 2.74E-18 8.37E-17 ? 5.98E-19 1.3E-20 ? 3.3E-21 -2.5E-19 ? 4.1E-19 -1.40E-19 ? -7.87E-20 115% 3.6948 18.52 ? 1.41 6.0 3.35E-16 ? 2.64E-18 1.03E-16 ? 4.79E-19 3.4E-19 ? 5.2E-20 3.8E-19 ? 4.1E-19 1.32E-19 ? 1.59E-19 88% 2.8732 14.42 ? 2.29 6.5 1.46E-16 ? 2.51E-18 4.46E-17 ? 5.07E-19 -4.0E-20 ? -1.7E-20 7.8E-19 ? 4.2E-19 9.29E-20 ? 1.61E-19 81% 2.6616 13.36 ? 5.36 7.0 8.63E-17 ? 2.06E-18 2.69E-17 ? 2.60E-19 -6.4E-20 ? -6.2E-20 5.3E-19 ? 4.4E-19 1.69E-19 ? 1.71E-19 42% 1.3479 6.78 ? 9.48 8.0 2.33E-17 ? 1.99E-18 7.11E-18 ? 2.63E-19 6.6E-20 ? 9.1E-20 8.0E-19 ? 4.4E-19 4.30E-19 ? 1.25E-19 -445% -14.5843 -75.03 ? -26 9.0 8.04E-18 ? 2.28E-18 2.21E-18 ? 3.07E-19 -4.0E-19 ? -1.6E-19 7.5E-19 ? 4.5E-19 9.99E-20 ? 1.57E-19 -267% -9.7113 -49.61 ? -108 109 Irradiation filename: au5.1c.adl.ih4 %P 40Ar(*?atm) 39Ar(K) 38Ar(Cl?atm) 37Ar(Ca) 36Ar(Atm) %Rad R Age (Ma) 3.0 3.73E-16 ? 3.14E-18 7.01E-18 ? 2.73E-19 4.2E-19 ? 1.7E-19 1.5E-19 ? 3.9E-19 1.28E-18 ? 8.64E-20 -1% -0.5311 -2.68 ? -23 3.3 1.21E-16 ? 2.43E-18 1.62E-17 ? 3.93E-19 1.5E-19 ? 9.0E-20 -5.1E-19 ? 4.3E-19 3.12E-19 ? 7.09E-20 24% 1.7779 8.94 ? 6.66 3.6 3.37E-16 ? 3.63E-18 7.84E-17 ? 1.24E-18 -1.4E-19 ? -3.5E-20 9.2E-20 ? 3.5E-19 3.11E-19 ? 8.18E-20 73% 3.1235 15.67 ? 1.60 4.0 5.48E-16 ? 3.55E-18 1.55E-16 ? 6.79E-19 1.1E-19 ? 1.1E-20 -2.5E-19 ? 5.0E-19 1.69E-19 ? 8.17E-20 91% 3.2058 16.08 ? 0.79 4.3 3.86E-16 ? 3.71E-18 1.14E-16 ? 9.86E-19 -9.2E-19 ? -1.3E-18 -7.5E-19 ? 4.5E-19 1.44E-19 ? 7.97E-20 89% 3.0169 15.14 ? 1.06 4.5 4.85E-15 ? 3.51E-18 1.49E-15 ? 3.19E-18 3.4E-18 ? 6.4E-20 -2.2E-19 ? 3.3E-19 7.94E-20 ? 1.49E-19 100% 3.2422 16.26 ? 0.15 4.8 9.97E-15 ? 1.15E-17 3.11E-15 ? 7.34E-18 7.6E-18 ? 5.3E-20 -6.0E-20 ? 4.0E-19 8.98E-19 ? 1.63E-19 97% 3.1201 15.65 ? 0.09 5.0 9.39E-15 ? 1.30E-17 2.93E-15 ? 9.90E-18 6.7E-18 ? 7.9E-20 -3.1E-19 ? 3.5E-19 6.89E-19 ? 1.17E-19 98% 3.1381 15.74 ? 0.08 5.3 4.47E-15 ? 4.04E-18 1.39E-15 ? 6.26E-18 3.3E-18 ? 5.8E-20 -3.7E-19 ? 3.7E-19 5.27E-19 ? 1.18E-19 97% 3.1052 15.58 ? 0.15 5.5 8.53E-15 ? 5.81E-18 2.63E-15 ? 3.02E-18 5.7E-18 ? 5.4E-20 6.7E-20 ? 2.8E-19 5.98E-19 ? 1.19E-19 98% 3.1717 15.91 ? 0.07 5.8 6.08E-15 ? 7.13E-18 1.88E-15 ? 1.55E-18 3.9E-18 ? 7.7E-20 3.4E-19 ? 3.7E-19 5.49E-19 ? 1.15E-19 97% 3.1505 15.81 ? 0.09 6.0 7.44E-15 ? 5.03E-18 2.29E-15 ? 2.81E-18 6.5E-18 ? 1.2E-19 -3.2E-19 ? 3.3E-19 4.67E-21 ? 1.36E-19 100% 3.2424 16.26 ? 0.09 6.5 6.94E-15 ? 7.28E-18 2.16E-15 ? 6.04E-18 4.9E-18 ? 7.6E-20 -3.2E-19 ? 3.1E-19 2.86E-19 ? 7.82E-20 99% 3.1704 15.91 ? 0.07 7.0 4.79E-15 ? 3.24E-18 1.47E-15 ? 2.48E-18 3.5E-18 ? 5.6E-20 -4.1E-20 ? 3.3E-19 2.29E-19 ? 8.10E-20 99% 3.2116 16.11 ? 0.09 8.0 4.20E-15 ? 1.01E-17 1.31E-15 ? 3.39E-18 3.0E-18 ? 4.1E-20 -3.4E-19 ? 4.5E-19 -1.50E-19 ? -1.49E-19 101% 3.2482 16.29 ? 0.18 9.0 8.17E-15 ? 1.06E-17 2.54E-15 ? 6.07E-18 5.9E-18 ? 8.7E-20 1.3E-20 ? 3.2E-19 1.77E-19 ? 7.94E-20 99% 3.1905 16.01 ? 0.06 110 Irradiation filename: au5.1c.adl.ih5 %P 40Ar(*?atm) 39Ar(K) 38Ar(Cl?atm) 37Ar(Ca) 36Ar(Atm) %Rad R Age (Ma) 3.0 9.16E-17 ? 2.06E-18 5.74E-18 ? 4.26E-19 -9.6E-21 ? -4.0E-20 -3.1E-19 ? 4.0E-19 1.69E-19 ? 9.19E-20 46% 7.2856 36.34 ? 24 3.3 4.27E-16 ? 3.54E-18 9.66E-17 ? 6.90E-19 -8.5E-20 ? -2.0E-20 -1.1E-18 ? 5.4E-19 2.03E-19 ? 9.08E-20 86% 3.7914 19.00 ? 1.41 3.6 4.82E-16 ? 3.71E-18 1.43E-16 ? 8.08E-19 1.9E-19 ? 2.1E-20 -8.5E-19 ? 3.7E-19 -1.40E-19 ? -9.32E-20 109% 3.6616 18.36 ? 0.98 4.0 7.47E-16 ? 6.83E-18 2.28E-16 ? 7.34E-19 6.4E-19 ? 5.0E-20 -1.0E-18 ? 3.9E-19 -1.44E-19 ? -8.44E-20 106% 3.4572 17.34 ? 0.57 4.3 2.62E-16 ? 2.46E-18 8.05E-17 ? 6.85E-19 3.7E-19 ? 6.6E-20 -8.1E-19 ? 4.3E-19 -8.65E-20 ? -8.55E-20 110% 3.5655 17.88 ? 1.59 4.5 4.28E-15 ? 5.12E-18 1.34E-15 ? 5.22E-18 3.1E-18 ? 4.0E-20 2.9E-19 ? 2.9E-19 -1.82E-20 ? -1.17E-19 100% 3.1994 16.05 ? 0.15 4.8 7.36E-15 ? 5.17E-18 2.31E-15 ? 5.49E-18 5.0E-18 ? 7.2E-20 -2.2E-19 ? 3.4E-19 2.96E-19 ? 7.16E-20 99% 3.1469 15.79 ? 0.06 5.0 2.32E-15 ? 6.12E-18 7.20E-16 ? 2.41E-18 2.0E-18 ? 7.6E-20 -3.5E-19 ? 3.5E-19 1.39E-19 ? 6.50E-20 98% 3.1647 15.88 ? 0.15 5.3 4.24E-15 ? 7.99E-18 1.33E-15 ? 2.14E-18 3.1E-18 ? 5.0E-20 -3.3E-19 ? 3.6E-19 7.78E-20 ? 7.00E-20 99% 3.1828 15.97 ? 0.09 5.5 2.80E-15 ? 4.32E-18 8.73E-16 ? 3.25E-18 2.4E-18 ? 8.5E-20 1.7E-19 ? 3.7E-19 3.92E-20 ? 6.57E-20 100% 3.1870 15.99 ? 0.13 5.8 1.40E-14 ? 8.98E-18 4.31E-15 ? 1.08E-17 9.8E-18 ? 1.0E-19 6.1E-21 ? 5.1E-19 9.67E-19 ? 8.06E-20 98% 3.1776 15.94 ? 0.05 6.0 1.99E-14 ? 3.39E-17 6.18E-15 ? 2.13E-17 1.6E-17 ? 2.3E-19 3.0E-19 ? 4.0E-19 7.74E-19 ? 8.65E-20 99% 3.1783 15.94 ? 0.07 6.5 8.88E-15 ? 1.11E-17 2.76E-15 ? 3.86E-18 6.7E-18 ? 5.6E-20 5.7E-19 ? 4.5E-19 1.03E-19 ? 6.28E-20 100% 3.2025 16.07 ? 0.05 7.0 1.67E-15 ? 5.73E-18 5.15E-16 ? 1.83E-18 1.1E-18 ? 4.6E-20 1.4E-18 ? 4.5E-19 -1.03E-19 ? -7.84E-20 102% 3.2907 16.51 ? 0.24 8.0 2.21E-15 ? 5.37E-18 6.85E-16 ? 2.01E-18 1.7E-18 ? 7.1E-20 -1.7E-19 ? 5.0E-19 8.89E-20 ? 7.69E-20 99% 3.1807 15.96 ? 0.18 9.0 8.74E-16 ? 3.28E-18 2.71E-16 ? 8.29E-19 8.0E-19 ? 5.3E-20 6.5E-19 ? 4.2E-19 7.32E-20 ? 7.99E-20 98% 3.1426 15.77 ? 0.44 111 Jumbo deposit step heating increments for 5 single adularia crystals (14-20 mesh size, 1.2-0.75 mm) of sample: HCN-3RE Irradiation filename: au5.1f.adl.ih.1 %P 40Ar(*?atm) 39Ar(K) 38Ar(Cl?atm) 37Ar(Ca) 36Ar(Atm) %Rad R Age (Ma) 3.0 3.42E-16 ? 3.70E-18 2.67E-18 ? 3.79E-19 4.4E-19 ? 1.7E-19 -5.2E-19 ? 3.5E-19 5.20E-19 ? 1.47E-19 55% 70.4089 323.89 ? 118 3.3 2.22E-16 ? 2.15E-18 2.79E-17 ? 4.13E-19 2.5E-19 ? 7.7E-20 1.0E-19 ? 4.5E-19 4.40E-19 ? 8.07E-20 42% 3.3163 16.63 ? 4.37 3.6 8.23E-16 ? 3.82E-18 2.19E-16 ? 9.69E-19 4.1E-19 ? 3.5E-20 -3.1E-19 ? 3.5E-19 2.00E-19 ? 8.55E-20 93% 3.4825 17.46 ? 0.59 4.0 2.14E-15 ? 3.81E-18 6.31E-16 ? 2.25E-18 1.8E-18 ? 5.1E-20 4.2E-19 ? 3.6E-19 -3.61E-21 ? -7.62E-20 100% 3.3862 16.98 ? 0.19 4.3 1.11E-15 ? 4.51E-18 3.38E-16 ? 2.04E-18 1.1E-18 ? 5.5E-20 4.3E-20 ? 3.2E-19 -9.26E-20 ? -8.16E-20 102% 3.3633 16.87 ? 0.38 4.5 3.77E-15 ? 4.57E-18 1.12E-15 ? 2.68E-18 2.8E-18 ? 8.0E-20 -4.5E-19 ? 2.8E-19 4.15E-19 ? 1.44E-19 97% 3.2498 16.30 ? 0.20 4.8 1.79E-14 ? 1.72E-17 5.36E-15 ? 1.30E-17 1.4E-17 ? 1.0E-19 -3.5E-19 ? 2.9E-19 7.39E-19 ? 1.82E-19 99% 3.2991 16.55 ? 0.07 5.0 8.10E-15 ? 1.07E-17 2.37E-15 ? 5.27E-18 5.6E-18 ? 7.4E-20 4.1E-19 ? 3.4E-19 1.09E-18 ? 1.42E-19 96% 3.2855 16.48 ? 0.10 5.3 7.53E-15 ? 6.49E-18 2.24E-15 ? 4.06E-18 5.2E-18 ? 8.3E-20 -9.7E-20 ? 3.5E-19 5.51E-19 ? 1.56E-19 98% 3.2919 16.51 ? 0.11 5.5 7.50E-15 ? 5.94E-18 2.23E-15 ? 6.30E-18 4.6E-18 ? 5.3E-20 -3.9E-19 ? 2.9E-19 3.00E-19 ? 8.96E-20 99% 3.3135 16.62 ? 0.08 5.8 7.33E-15 ? 5.94E-18 2.19E-15 ? 5.86E-18 5.2E-18 ? 9.9E-20 1.4E-19 ? 3.4E-19 3.42E-19 ? 8.94E-20 99% 3.2930 16.52 ? 0.08 6.0 1.09E-14 ? 8.21E-18 3.22E-15 ? 5.64E-18 6.8E-18 ? 7.9E-20 -5.8E-20 ? 4.3E-19 1.52E-19 ? 8.41E-20 100% 3.3527 16.82 ? 0.05 6.5 6.22E-15 ? 3.52E-17 1.81E-15 ? 4.42E-18 4.5E-18 ? 7.7E-20 -2.9E-19 ? 4.1E-19 1.35E-19 ? 7.33E-20 99% 3.4020 17.06 ? 0.12 7.0 1.09E-14 ? 8.21E-18 3.22E-15 ? 5.64E-18 6.8E-18 ? 7.9E-20 -5.8E-20 ? 4.3E-19 1.52E-19 ? 8.41E-20 100% 3.3527 16.82 ? 0.05 8.0 6.66E-16 ? 3.61E-18 1.95E-16 ? 1.16E-18 2.2E-19 ? 1.6E-20 -5.9E-19 ? 3.9E-19 -8.19E-20 ? -8.37E-20 104% 3.5297 17.70 ? 0.65 9.0 7.72E-17 ? 1.90E-18 2.09E-17 ? 4.63E-19 -3.1E-19 ? -7.3E-19 -6.7E-19 ? 3.9E-19 -4.70E-20 ? -7.73E-20 118% 4.3562 21.82 ? 5.51 112 Irradiation filename: au5.1f.adl.ih.2 %P 40Ar(*?atm) 39Ar(K) 38Ar(Cl?atm) 37Ar(Ca) 36Ar(Atm) %Rad R Age (Ma) 3.0 1.87E-16 ? 1.85E-18 2.99E-18 ? 4.15E-19 1.6E-19 ? 1.7E-19 -5.1E-19 ? 4.0E-19 6.31E-19 ? 8.29E-20 0% 0.1822 0.92 ? 74 3.3 1.49E-16 ? 2.23E-18 3.17E-17 ? 6.09E-19 2.9E-19 ? 1.0E-19 2.6E-19 ? 4.4E-19 4.75E-20 ? 8.46E-20 91% 4.2523 21.30 ? 3.99 3.6 2.39E-16 ? 3.12E-18 6.32E-17 ? 5.75E-19 7.8E-20 ? 2.2E-20 1.6E-18 ? 5.6E-19 1.35E-22 ? 1.94E-20 100% 3.7795 18.94 ? 0.55 4.0 3.24E-16 ? 1.81E-18 9.57E-17 ? 9.17E-19 2.2E-19 ? 3.0E-20 -2.4E-20 ? 4.4E-19 7.43E-21 ? 7.95E-20 99% 3.3576 16.84 ? 1.25 4.3 3.79E-16 ? 3.18E-18 1.10E-16 ? 9.66E-19 1.8E-19 ? 3.3E-20 5.0E-19 ? 5.1E-19 -1.14E-19 ? -1.17E-19 109% 3.7612 18.85 ? 1.59 4.5 1.91E-15 ? 5.08E-18 5.73E-16 ? 1.97E-18 2.0E-18 ? 6.3E-20 -2.8E-19 ? 4.0E-19 1.29E-19 ? 8.04E-20 98% 3.2721 16.41 ? 0.22 4.8 8.10E-15 ? 5.62E-18 2.46E-15 ? 4.50E-18 7.6E-18 ? 1.2E-19 1.6E-19 ? 3.9E-19 3.91E-19 ? 7.71E-20 99% 3.2393 16.25 ? 0.06 5.0 9.38E-15 ? 5.05E-18 2.84E-15 ? 1.07E-17 7.2E-18 ? 8.4E-20 -3.3E-19 ? 4.4E-19 2.95E-19 ? 7.44E-20 99% 3.2674 16.39 ? 0.07 5.3 9.81E-15 ? 7.07E-18 2.97E-15 ? 7.74E-18 6.7E-18 ? 6.6E-20 -7.0E-20 ? 3.5E-19 2.52E-19 ? 8.96E-20 99% 3.2803 16.45 ? 0.06 5.5 6.45E-15 ? 5.49E-18 1.95E-15 ? 7.14E-18 4.4E-18 ? 3.4E-20 -9.9E-20 ? 3.7E-19 6.40E-20 ? 6.72E-20 100% 3.2990 16.55 ? 0.08 5.8 5.33E-15 ? 4.41E-18 1.61E-15 ? 4.79E-18 4.0E-18 ? 5.7E-20 -5.3E-21 ? 4.3E-19 -2.03E-19 ? -1.42E-19 101% 3.3413 16.76 ? 0.14 6.0 3.55E-15 ? 4.91E-18 1.07E-15 ? 4.62E-18 1.8E-18 ? 4.3E-20 -3.7E-19 ? 4.6E-19 -5.75E-20 ? -8.04E-20 100% 3.3316 16.71 ? 0.13 6.5 6.32E-15 ? 3.74E-18 1.91E-15 ? 6.50E-18 4.2E-18 ? 4.9E-20 2.0E-19 ? 4.2E-19 2.19E-20 ? 8.60E-20 100% 3.3062 16.58 ? 0.09 7.0 6.02E-15 ? 5.12E-18 1.81E-15 ? 3.28E-18 4.1E-18 ? 5.4E-20 -4.2E-20 ? 3.5E-19 -5.67E-20 ? -8.26E-20 100% 3.3409 16.76 ? 0.08 8.0 6.47E-15 ? 4.56E-18 1.96E-15 ? 5.19E-18 3.7E-18 ? 5.8E-20 -1.3E-19 ? 3.1E-19 -2.37E-19 ? -1.40E-19 101% 3.3418 16.76 ? 0.12 9.0 5.34E-15 ? 3.71E-18 1.60E-15 ? 2.43E-18 4.6E-18 ? 1.5E-19 1.2E-19 ? 3.7E-19 1.01E-19 ? 8.90E-20 99% 3.3062 16.58 ? 0.09 113 Irradiation filename: au5.1f.adl.ih.3 %P 40Ar(*?atm) 39Ar(K) 38Ar(Cl?atm) 37Ar(Ca) 36Ar(Atm) %Rad R Age (Ma) 3.0 2.24E-16 ? 2.03E-18 3.64E-18 ? 3.86E-19 -8.6E-20 ? -2.9E-19 -1.0E-18 ? 3.9E-19 8.82E-19 ? 1.36E-19 -16% -10.1138 -51.70 ? -76 3.3 1.60E-16 ? 2.65E-18 3.76E-17 ? 4.21E-19 -3.2E-19 ? -8.6E-19 -3.7E-19 ? 4.0E-19 2.09E-19 ? 1.41E-19 61% 2.6192 13.15 ? 5.59 3.6 3.37E-16 ? 2.42E-18 9.36E-17 ? 4.84E-19 1.6E-19 ? 2.9E-20 -5.0E-19 ? 4.6E-19 1.90E-19 ? 1.40E-19 83% 2.9954 15.03 ? 2.22 4.0 6.85E-16 ? 3.50E-18 2.00E-16 ? 8.73E-19 5.3E-19 ? 5.0E-20 -7.1E-19 ? 3.6E-19 1.35E-19 ? 1.35E-19 94% 3.2295 16.20 ? 1.01 4.3 6.09E-16 ? 3.74E-18 1.81E-16 ? 7.92E-19 4.7E-19 ? 5.0E-20 -9.9E-20 ? 3.9E-19 2.29E-19 ? 8.59E-20 89% 2.9821 14.96 ? 0.71 4.5 2.15E-15 ? 6.01E-18 6.56E-16 ? 3.51E-18 1.2E-18 ? 2.8E-20 -5.5E-19 ? 5.3E-19 -9.35E-20 ? -1.40E-19 101% 3.3245 16.67 ? 0.33 4.8 1.04E-14 ? 9.46E-18 3.14E-15 ? 5.79E-18 7.4E-18 ? 7.8E-20 -5.5E-19 ? 5.0E-19 1.84E-19 ? 8.57E-20 99% 3.2994 16.55 ? 0.05 5.0 1.17E-14 ? 8.86E-18 3.51E-15 ? 4.67E-18 8.0E-18 ? 1.0E-19 -1.0E-18 ? 4.8E-19 5.08E-19 ? 9.80E-20 99% 3.2894 16.50 ? 0.05 5.3 4.97E-15 ? 3.68E-18 1.50E-15 ? 2.27E-18 3.6E-18 ? 5.7E-20 4.7E-19 ? 4.9E-19 1.18E-19 ? 8.36E-20 99% 3.2889 16.50 ? 0.09 5.5 3.27E-15 ? 3.31E-18 9.81E-16 ? 2.18E-18 1.8E-18 ? 5.3E-20 -2.0E-18 ? 6.2E-19 -5.22E-20 ? -1.07E-19 100% 3.3492 16.80 ? 0.17 5.8 1.83E-15 ? 5.94E-18 5.46E-16 ? 1.71E-18 1.0E-18 ? 3.7E-20 -1.5E-19 ? 4.8E-19 -2.78E-19 ? -1.35E-19 104% 3.4882 17.49 ? 0.37 6.0 1.80E-15 ? 7.03E-18 5.36E-16 ? 1.70E-18 1.3E-18 ? 5.3E-20 -5.4E-19 ? 4.9E-19 4.95E-21 ? 8.89E-20 100% 3.3566 16.83 ? 0.26 6.5 8.96E-15 ? 1.35E-17 2.71E-15 ? 5.48E-18 6.1E-18 ? 8.1E-20 -2.0E-19 ? 5.0E-19 1.32E-19 ? 9.07E-20 100% 3.2848 16.48 ? 0.06 7.0 1.59E-15 ? 7.24E-18 4.73E-16 ? 1.91E-18 1.0E-18 ? 3.3E-20 -9.3E-19 ? 4.0E-19 -1.35E-20 ? -1.01E-19 100% 3.3729 16.92 ? 0.33 8.0 2.76E-16 ? 2.28E-18 8.01E-17 ? 7.56E-19 -5.9E-20 ? -1.4E-20 -4.0E-19 ? 4.3E-19 -2.77E-19 ? -1.37E-19 130% 4.4644 22.36 ? 2.55 9.0 6.44E-17 ? 2.47E-18 1.90E-17 ? 4.72E-19 -6.7E-20 ? -1.0E-19 -4.2E-19 ? 4.5E-19 1.33E-20 ? 9.30E-20 94% 3.1824 15.96 ? 7.31 114 Irradiation filename: au5.1f.adl.ih.4 %P 40Ar(*?atm) 39Ar(K) 38Ar(Cl?atm) 37Ar(Ca) 36Ar(Atm) %Rad R Age (Ma) 3.0 5.96E-16 ? 2.72E-18 7.03E-18 ? 3.25E-19 5.8E-19 ? 2.5E-19 -1.8E-19 ? 4.1E-19 2.18E-18 ? 1.62E-19 -8% -6.8368 -34.78 ? -45 3.3 2.31E-16 ? 3.44E-18 5.40E-17 ? 5.26E-19 6.8E-20 ? 2.9E-20 -5.0E-19 ? 4.2E-19 4.54E-19 ? 1.52E-19 42% 1.7858 8.98 ? 4.19 3.6 9.08E-16 ? 4.71E-18 2.61E-16 ? 6.33E-19 3.7E-19 ? 3.8E-20 5.2E-22 ? 5.6E-19 4.31E-19 ? 1.54E-19 86% 2.9841 14.97 ? 0.88 4.0 7.60E-15 ? 3.66E-18 2.24E-15 ? 3.64E-18 4.5E-18 ? 4.7E-20 -2.1E-19 ? 5.6E-19 3.76E-19 ? 1.84E-19 99% 3.3360 16.73 ? 0.12 4.3 1.02E-14 ? 9.73E-18 2.97E-15 ? 4.53E-18 8.8E-18 ? 1.3E-19 -4.3E-19 ? 3.7E-19 1.54E-18 ? 1.70E-19 96% 3.2932 16.52 ? 0.09 4.5 3.69E-15 ? 8.96E-18 1.04E-15 ? 3.58E-18 2.9E-18 ? 8.1E-20 1.1E-18 ? 6.5E-19 1.21E-18 ? 1.51E-19 90% 3.2146 16.13 ? 0.23 4.8 5.06E-15 ? 7.31E-18 1.45E-15 ? 3.89E-18 3.9E-18 ? 6.6E-20 1.0E-18 ? 6.2E-19 1.10E-18 ? 1.49E-19 94% 3.2738 16.42 ? 0.16 5.0 3.78E-15 ? 6.31E-18 1.11E-15 ? 3.95E-18 3.0E-18 ? 8.8E-20 1.3E-18 ? 6.6E-19 3.34E-19 ? 1.85E-19 97% 3.3162 16.63 ? 0.26 5.3 4.53E-15 ? 7.08E-18 1.33E-15 ? 4.24E-18 3.1E-18 ? 5.2E-20 1.3E-18 ? 6.2E-19 4.26E-19 ? 1.44E-19 97% 3.3041 16.57 ? 0.17 5.5 7.21E-15 ? 6.34E-18 2.13E-15 ? 2.48E-18 6.4E-18 ? 1.3E-19 5.3E-19 ? 6.4E-19 5.05E-19 ? 1.46E-19 98% 3.3111 16.61 ? 0.10 5.8 2.69E-15 ? 5.74E-18 7.97E-16 ? 2.74E-18 1.7E-18 ? 4.3E-20 1.6E-18 ? 7.1E-19 4.17E-19 ? 1.43E-19 95% 3.2223 16.16 ? 0.27 6.0 2.22E-15 ? 2.96E-18 6.48E-16 ? 2.09E-18 2.1E-18 ? 7.3E-20 -6.7E-19 ? 4.2E-19 -2.14E-19 ? -1.27E-19 103% 3.5212 17.66 ? 0.30 6.5 8.73E-16 ? 4.13E-18 2.60E-16 ? 1.63E-18 3.5E-19 ? 2.1E-20 -4.5E-19 ? 4.1E-19 3.91E-20 ? 7.93E-20 99% 3.3078 16.59 ? 0.47 7.0 2.76E-16 ? 2.68E-18 8.01E-17 ? 9.28E-19 7.0E-20 ? 1.3E-20 -5.7E-19 ? 4.7E-19 -1.22E-19 ? -7.32E-20 113% 3.9008 19.55 ? 1.38 8.0 5.40E-17 ? 1.90E-18 1.57E-17 ? 4.09E-19 -7.4E-20 ? -1.4E-19 -6.0E-19 ? 4.0E-19 -1.75E-19 ? -7.40E-20 196% 6.7456 33.67 ? 7.02 9.0 2.73E-17 ? 1.41E-18 7.30E-18 ? 4.47E-19 -2.1E-19 ? -2.7E-19 -1.4E-18 ? 4.3E-19 -1.39E-19 ? -8.07E-20 251% 9.3775 46.64 ? 16 115 Irradiation filename: au5.1f.adl.ih.5 %P 40Ar(*?atm) 39Ar(K) 38Ar(Cl?atm) 37Ar(Ca) 36Ar(Atm) %Rad R Age (Ma) 3.0 3.93E-16 ? 3.38E-18 2.17E-18 ? 3.35E-19 -5.6E-20 ? -2.9E-19 2.7E-19 ? 4.2E-19 1.48E-18 ? 8.28E-20 -11% -20.3667 -105.66 ? -224 3.3 n/a ? n/a 3.49E-18 ? 2.88E-19 6.7E-19 ? 1.6E-19 -1.2E-19 ? 5.1E-19 3.94E-18 ? 1.10E-19 n/a n/a n/a ? n/a 3.6 3.49E-16 ? 2.56E-18 6.91E-17 ? 9.46E-19 6.5E-20 ? 1.4E-20 5.4E-19 ? 3.2E-19 3.67E-19 ? 6.80E-20 69% 3.4805 17.45 ? 1.51 4.0 7.37E-16 ? 4.45E-18 2.04E-16 ? 1.21E-18 4.9E-19 ? 3.9E-20 3.8E-19 ? 3.5E-19 1.20E-19 ? 7.23E-20 95% 3.4411 17.26 ? 0.55 4.3 6.31E-16 ? 5.03E-18 1.88E-16 ? 1.28E-18 2.9E-19 ? 3.4E-20 5.4E-19 ? 4.2E-19 8.86E-20 ? 8.60E-20 96% 3.2158 16.13 ? 0.70 4.5 6.81E-15 ? 9.27E-18 2.07E-15 ? 3.62E-18 4.7E-18 ? 9.3E-20 -4.1E-19 ? 3.0E-19 1.89E-19 ? 7.94E-20 99% 3.2541 16.32 ? 0.07 4.8 1.95E-14 ? 1.06E-17 5.86E-15 ? 1.07E-17 1.4E-17 ? 9.5E-20 1.1E-19 ? 2.7E-19 9.32E-19 ? 7.31E-20 99% 3.2768 16.44 ? 0.04 5.0 9.40E-15 ? 1.26E-17 2.79E-15 ? 4.59E-18 8.2E-18 ? 1.6E-19 7.2E-19 ? 2.8E-19 9.37E-19 ? 7.50E-20 97% 3.2690 16.40 ? 0.05 5.3 8.95E-15 ? 7.24E-18 2.65E-15 ? 3.83E-18 6.7E-18 ? 6.5E-20 5.0E-19 ? 3.6E-19 4.94E-19 ? 7.56E-20 98% 3.3222 16.66 ? 0.05 5.5 4.34E-15 ? 7.05E-18 1.32E-15 ? 3.23E-18 2.6E-18 ? 4.8E-20 2.7E-19 ? 4.3E-19 2.42E-19 ? 7.65E-20 98% 3.2245 16.17 ? 0.10 5.8 2.75E-15 ? 5.77E-18 8.18E-16 ? 2.25E-18 1.8E-18 ? 4.2E-20 -3.7E-19 ? 2.7E-19 1.83E-19 ? 9.13E-20 98% 3.2872 16.49 ? 0.18 6.0 4.24E-15 ? 7.29E-18 1.26E-15 ? 3.76E-18 1.9E-18 ? 3.2E-20 9.7E-20 ? 4.3E-19 4.07E-19 ? 8.43E-20 97% 3.2540 16.32 ? 0.11 6.5 7.69E-15 ? 1.06E-17 2.31E-15 ? 6.05E-18 6.0E-18 ? 1.3E-19 5.2E-19 ? 5.6E-19 3.00E-19 ? 7.10E-20 99% 3.2892 16.50 ? 0.07 7.0 1.02E-14 ? 8.61E-18 3.07E-15 ? 5.76E-18 9.0E-18 ? 2.0E-19 1.7E-18 ? 4.8E-19 1.09E-19 ? 8.65E-20 100% 3.3062 16.58 ? 0.05 8.0 1.07E-14 ? 1.21E-17 3.20E-15 ? 7.41E-18 5.6E-18 ? 8.3E-20 5.5E-19 ? 3.8E-19 -7.37E-20 ? -1.34E-19 100% 3.3336 16.72 ? 0.08 9.0 1.12E-15 ? 4.33E-18 3.35E-16 ? 1.21E-18 6.6E-19 ? 3.9E-20 7.8E-19 ? 4.9E-19 -6.30E-20 ? -1.27E-19 102% 3.3794 16.95 ? 0.57 116 Ten Mile deposit step heating increments for 5 single adularia crystals (14-20 mesh size, 1.2-0.75 mm) of sample: HCN-4 Irradiation filename: au5.1h.adl.ih1 %P 40Ar(*?atm) 39Ar(K) 38Ar(Cl?atm) 37Ar(Ca) 36Ar(Atm) %Rad R Age (Ma) 3.0 3.30E-15 ? 4.23E-18 3.86E-18 ? 4.06E-19 2.0E-18 ? 1.5E-19 -6.9E-19 ? 3.3E-19 1.11E-17 ? 1.58E-19 0% 2.3137 11.62 ? 640 3.3 3.19E-15 ? 5.21E-18 2.28E-17 ? 6.49E-19 1.8E-18 ? 1.6E-19 -4.5E-19 ? 4.2E-19 1.02E-17 ? 1.26E-19 5% 7.4235 37.02 ? 28 3.6 1.88E-15 ? 2.69E-18 1.19E-16 ? 7.25E-19 1.2E-18 ? 7.9E-20 2.8E-19 ? 4.0E-19 4.19E-18 ? 1.98E-19 34% 5.3753 26.88 ? 2.54 4.0 2.02E-15 ? 4.68E-18 3.19E-16 ? 1.23E-18 1.1E-18 ? 5.5E-20 -1.9E-19 ? 4.3E-19 2.94E-18 ? 1.05E-19 57% 3.6060 18.08 ? 0.51 4.3 1.04E-15 ? 1.68E-18 2.02E-16 ? 1.66E-18 4.9E-19 ? 4.5E-20 -1.0E-20 ? 3.6E-19 1.14E-18 ? 9.53E-20 67% 3.4610 17.36 ? 0.74 4.5 1.34E-15 ? 3.96E-18 2.42E-16 ? 1.45E-18 1.0E-18 ? 5.9E-20 1.2E-19 ? 3.2E-19 1.60E-18 ? 9.21E-20 65% 3.5858 17.98 ? 0.60 4.8 8.89E-16 ? 3.59E-18 2.25E-16 ? 2.51E-18 5.3E-19 ? 3.8E-20 3.4E-19 ? 4.3E-19 3.29E-19 ? 8.39E-20 89% 3.5184 17.64 ? 0.60 5.0 1.10E-15 ? 4.13E-18 2.41E-16 ? 1.26E-18 1.2E-18 ? 6.8E-20 4.5E-19 ? 4.5E-19 9.86E-19 ? 9.27E-20 74% 3.3659 16.88 ? 0.59 5.3 3.23E-15 ? 3.78E-18 7.71E-16 ? 2.18E-18 2.7E-18 ? 6.1E-20 4.4E-19 ? 4.4E-19 2.27E-18 ? 8.65E-20 79% 3.3143 16.62 ? 0.18 5.5 1.01E-14 ? 9.27E-18 2.78E-15 ? 2.71E-18 7.1E-18 ? 8.3E-20 -1.3E-19 ? 4.6E-19 2.98E-18 ? 1.03E-19 91% 3.3229 16.67 ? 0.06 5.8 1.91E-14 ? 2.07E-17 5.63E-15 ? 1.55E-17 1.3E-17 ? 1.4E-19 1.1E-19 ? 4.0E-19 1.63E-18 ? 1.00E-19 97% 3.2967 16.54 ? 0.06 6.0 1.54E-14 ? 1.15E-17 4.61E-15 ? 8.85E-18 1.2E-17 ? 1.1E-19 -4.8E-19 ? 3.4E-19 8.99E-19 ? 8.33E-20 98% 3.2815 16.46 ? 0.04 6.5 7.57E-15 ? 8.82E-18 2.27E-15 ? 2.61E-18 4.5E-18 ? 6.2E-20 -4.1E-19 ? 3.5E-19 2.81E-19 ? 7.93E-20 99% 3.2985 16.54 ? 0.06 7.0 1.94E-15 ? 3.32E-18 5.77E-16 ? 2.75E-18 7.5E-19 ? 3.3E-20 -1.3E-19 ? 3.5E-19 2.09E-19 ? 7.51E-20 97% 3.2547 16.33 ? 0.21 8.0 1.35E-15 ? 3.43E-18 4.00E-16 ? 3.34E-18 4.9E-19 ? 2.3E-20 -8.2E-20 ? 3.6E-19 8.42E-20 ? 7.71E-20 98% 3.3041 16.57 ? 0.32 9.0 1.95E-15 ? 5.89E-18 5.86E-16 ? 3.54E-18 1.5E-18 ? 5.4E-20 -2.9E-19 ? 4.2E-19 3.76E-20 ? 8.97E-20 99% 3.3115 16.61 ? 0.25 117 Irradiation filename: au5.1h.adl.ih2 %P 40Ar(*?atm) 39Ar(K) 38Ar(Cl?atm) 37Ar(Ca) 36Ar(Atm) %Rad R Age (Ma) 3.0 9.51E-16 ? 2.68E-18 1.66E-19 ? 4.10E-19 1.2E-18 ? 2.9E-19 -6.9E-19 ? 4.0E-19 3.11E-18 ? 8.97E-20 3% 196.9579 790.78 ? 7936 3.3 4.08E-15 ? 7.99E-18 6.26E-18 ? 3.49E-19 3.2E-18 ? 3.2E-19 -3.0E-19 ? 3.4E-19 1.36E-17 ? 1.75E-19 1% 7.1064 35.46 ? 258 3.6 1.79E-15 ? 4.37E-18 6.84E-17 ? 1.36E-18 1.8E-18 ? 2.1E-19 -5.1E-19 ? 3.3E-19 5.19E-18 ? 1.20E-19 14% 3.7373 18.73 ? 4.33 4.0 1.37E-15 ? 2.72E-18 2.57E-16 ? 1.75E-18 1.4E-18 ? 1.1E-19 -4.8E-19 ? 3.8E-19 1.71E-18 ? 9.43E-20 63% 3.3759 16.93 ? 0.58 4.3 1.04E-15 ? 5.16E-18 1.54E-16 ? 7.69E-19 6.0E-19 ? 1.1E-19 -7.7E-19 ? 4.5E-19 1.47E-18 ? 1.73E-19 58% 3.8997 19.54 ? 1.68 4.5 1.60E-14 ? 2.12E-17 4.16E-15 ? 4.77E-18 1.2E-17 ? 1.3E-19 5.6E-19 ? 4.4E-19 8.04E-18 ? 1.31E-19 85% 3.2781 16.44 ? 0.06 4.8 1.75E-14 ? 1.57E-17 5.28E-15 ? 6.13E-18 1.2E-17 ? 6.5E-20 4.3E-19 ? 4.4E-19 1.03E-18 ? 8.71E-20 98% 3.2636 16.37 ? 0.03 5.0 1.21E-14 ? 9.48E-18 3.66E-15 ? 8.29E-18 8.6E-18 ? 6.7E-20 3.9E-19 ? 4.3E-19 2.64E-19 ? 7.64E-20 99% 3.2892 16.50 ? 0.05 5.3 3.57E-15 ? 5.45E-18 1.08E-15 ? 3.09E-18 2.4E-18 ? 4.0E-20 2.9E-20 ? 3.9E-19 4.42E-20 ? 8.69E-20 100% 3.2934 16.52 ? 0.13 5.5 1.50E-15 ? 2.69E-18 4.50E-16 ? 2.93E-18 7.9E-19 ? 2.3E-20 1.2E-19 ? 3.6E-19 -8.97E-20 ? -7.58E-20 102% 3.3922 17.01 ? 0.27 5.8 1.24E-15 ? 3.62E-18 3.66E-16 ? 1.80E-18 9.3E-19 ? 4.7E-20 1.8E-19 ? 4.3E-19 -5.46E-20 ? -7.37E-20 101% 3.4145 17.12 ? 0.31 6.0 6.17E-16 ? 5.11E-18 1.85E-16 ? 9.80E-19 2.0E-19 ? 1.7E-20 -8.8E-21 ? 4.0E-19 -3.02E-20 ? -7.22E-20 101% 3.3880 16.99 ? 0.60 6.5 8.43E-16 ? 4.48E-18 2.49E-16 ? 1.52E-18 4.2E-19 ? 3.5E-20 -2.2E-19 ? 3.9E-19 -2.39E-20 ? -8.07E-20 101% 3.4113 17.11 ? 0.50 7.0 4.63E-16 ? 4.71E-18 1.38E-16 ? 9.96E-19 -4.2E-20 ? -6.6E-21 -5.7E-19 ? 4.1E-19 -2.53E-19 ? -1.02E-19 116% 3.8842 19.47 ? 1.11 8.0 7.72E-16 ? 4.89E-18 2.27E-16 ? 1.17E-18 3.3E-19 ? 2.9E-20 -3.9E-20 ? 3.6E-19 -5.00E-20 ? -7.56E-20 102% 3.4576 17.34 ? 0.51 9.0 4.70E-16 ? 2.68E-18 1.43E-16 ? 1.23E-18 1.9E-20 ? 2.2E-21 -4.2E-19 ? 3.5E-19 -8.42E-21 ? -8.33E-20 101% 3.3012 16.56 ? 0.88 118 Irradiation filename: au5.1h.adl.ih3 %P 40Ar(*?atm) 39Ar(K) 38Ar(Cl?atm) 37Ar(Ca) 36Ar(Atm) %Rad R Age (Ma) 3.0 1.23E-15 ? 3.42E-18 2.62E-18 ? 3.39E-19 9.6E-19 ? 1.2E-19 5.6E-19 ? 4.3E-19 4.22E-18 ? 1.06E-19 -1% -5.6097 -28.49 ? -444 3.3 8.08E-16 ? 3.77E-18 4.59E-17 ? 4.85E-19 5.9E-19 ? 9.5E-20 7.8E-19 ? 4.9E-19 2.21E-18 ? 1.10E-19 19% 3.3909 17.01 ? 3.76 3.6 1.20E-15 ? 2.58E-18 2.66E-16 ? 2.23E-18 6.6E-19 ? 4.5E-20 3.2E-19 ? 4.3E-19 1.10E-18 ? 9.37E-20 73% 3.2899 16.50 ? 0.56 4.0 1.65E-14 ? 1.47E-17 4.67E-15 ? 7.83E-18 1.1E-17 ? 1.0E-19 -1.0E-19 ? 5.0E-19 4.28E-18 ? 1.15E-19 92% 3.2577 16.34 ? 0.05 4.3 9.17E-15 ? 9.73E-18 2.76E-15 ? 5.99E-18 6.1E-18 ? 8.7E-20 6.5E-19 ? 4.5E-19 1.74E-19 ? 1.43E-19 99% 3.3001 16.55 ? 0.09 4.5 2.09E-15 ? 4.96E-18 6.20E-16 ? 1.67E-18 1.5E-18 ? 5.9E-20 -5.8E-19 ? 3.7E-19 -3.68E-20 ? -7.39E-20 101% 3.3913 17.01 ? 0.19 4.8 6.91E-16 ? 2.70E-18 2.08E-16 ? 1.05E-18 2.5E-19 ? 2.1E-20 -7.4E-19 ? 3.0E-19 -6.18E-20 ? -7.80E-20 103% 3.4070 17.09 ? 0.57 5.0 4.18E-16 ? 2.37E-18 1.22E-16 ? 9.79E-19 -4.0E-19 ? -1.1E-19 -1.9E-20 ? 4.4E-19 -4.93E-20 ? -7.66E-20 103% 3.5326 17.71 ? 0.94 5.3 5.62E-17 ? 2.46E-18 1.62E-17 ? 3.48E-19 1.2E-19 ? 1.0E-19 -5.1E-19 ? 3.4E-19 -1.23E-20 ? -8.18E-20 106% 3.7019 18.56 ? 7.55 5.5 5.77E-18 ? 1.81E-18 1.29E-19 ? 3.57E-19 6.0E-21 ? 1.6E-19 -8.3E-19 ? 4.1E-19 -1.00E-19 ? -7.69E-20 613% 274.8279 1027.65 ? 2516 5.8 4.91E-18 ? 1.75E-18 -8.98E-20 ? -2.80E-19 4.9E-20 ? 2.1E-19 -4.8E-19 ? 3.8E-19 3.73E-20 ? 8.34E-20 -124% 68.7209 316.77 ? 2312 6.0 7.96E-19 ? 2.26E-18 8.72E-20 ? 3.07E-19 -1.1E-19 ? -2.0E-19 3.7E-19 ? 3.5E-19 1.57E-19 ? 1.99E-19 -5747% -525.8438 n/a ? n/a 6.5 3.42E-18 ? 1.97E-18 1.14E-19 ? 2.31E-19 -1.1E-19 ? -2.2E-19 3.9E-19 ? 4.4E-19 4.35E-19 ? 1.28E-19 -3661% -1096.3408 n/a ? n/a 7.0 1.51E-18 ? 2.15E-18 -9.21E-19 ? -4.27E-19 -4.0E-20 ? -1.9E-19 3.5E-19 ? 4.5E-19 5.05E-19 ? 1.33E-19 -9807% 160.3184 667.56 ? 359 8.0 1.36E-18 ? 1.97E-18 -3.16E-19 ? -3.06E-19 -1.8E-19 ? -2.0E-19 -1.4E-19 ? 4.4E-19 3.50E-19 ? 1.33E-19 -7479% 323.4493 1161.19 ? 1226 9.0 1.31E-18 ? 2.08E-18 6.47E-20 ? 2.61E-19 -2.6E-19 ? -2.1E-19 -2.9E-19 ? 3.5E-19 4.10E-19 ? 1.32E-19 -9125% -1852.5235 n/a ? na 119 Irradiation filename: au5.1h.adl.ih4 %P 40Ar(*?atm) 39Ar(K) 38Ar(Cl?atm) 37Ar(Ca) 36Ar(Atm) %Rad R Age (Ma) 3.0 1.25E-15 ? 7.03E-18 2.82E-18 ? 3.21E-19 6.2E-19 ? 1.7E-19 -7.5E-19 ? 4.9E-19 4.12E-18 ? 1.12E-19 3% 12.1610 60.26 ? 353 3.3 4.87E-16 ? 3.11E-18 2.07E-17 ? 4.11E-19 3.4E-19 ? 6.4E-20 -1.1E-18 ? 3.8E-19 1.29E-18 ? 8.56E-20 22% 5.1477 25.75 ? 6.83 3.6 3.89E-16 ? 3.20E-18 7.82E-17 ? 5.83E-19 8.3E-20 ? 1.7E-20 -1.1E-18 ? 4.1E-19 -1.58E-20 ? -1.34E-19 101% 5.0290 25.16 ? 2.55 4.0 1.97E-15 ? 3.75E-18 2.14E-16 ? 1.15E-18 1.2E-18 ? 4.4E-20 -7.7E-19 ? 4.0E-19 3.50E-18 ? 1.88E-19 47% 4.3608 21.84 ? 1.33 4.3 3.18E-15 ? 3.14E-18 4.33E-16 ? 1.06E-18 2.2E-18 ? 9.7E-20 1.5E-18 ? 5.1E-19 5.92E-18 ? 1.11E-19 45% 3.3074 16.59 ? 0.40 4.5 2.01E-14 ? 1.95E-17 5.78E-15 ? 9.83E-18 1.2E-17 ? 9.6E-20 3.1E-19 ? 4.6E-19 3.61E-18 ? 1.05E-19 95% 3.2837 16.47 ? 0.04 4.8 2.02E-14 ? 9.99E-18 6.12E-15 ? 6.81E-18 1.4E-17 ? 1.4E-19 1.2E-19 ? 5.4E-19 5.73E-20 ? 1.39E-19 100% 3.3043 16.57 ? 0.04 5.0 3.72E-15 ? 2.63E-18 1.11E-15 ? 2.80E-18 2.9E-18 ? 4.7E-20 -1.6E-19 ? 4.8E-19 -5.66E-20 ? -8.24E-20 100% 3.3622 16.86 ? 0.12 5.3 1.50E-15 ? 4.72E-18 4.46E-16 ? 1.03E-18 2.2E-18 ? 1.4E-19 -6.7E-20 ? 5.2E-19 -1.94E-19 ? -1.33E-19 104% 3.4894 17.50 ? 0.45 5.5 9.26E-16 ? 3.80E-18 2.80E-16 ? 2.01E-18 3.2E-19 ? 2.4E-20 1.6E-19 ? 5.2E-19 -4.29E-19 ? -1.28E-19 114% 3.7588 18.84 ? 0.69 5.8 7.19E-16 ? 3.91E-18 2.15E-16 ? 1.13E-18 2.9E-19 ? 2.7E-20 -3.9E-19 ? 4.7E-19 6.04E-20 ? 8.10E-20 98% 3.2603 16.35 ? 0.57 6.0 5.12E-16 ? 3.08E-18 1.54E-16 ? 8.13E-19 3.0E-19 ? 3.6E-20 -2.5E-19 ? 3.9E-19 8.50E-20 ? 8.41E-20 95% 3.1658 15.88 ? 0.82 6.5 8.34E-16 ? 2.86E-18 2.47E-16 ? 1.42E-18 4.8E-19 ? 4.8E-20 -5.5E-19 ? 5.2E-19 6.75E-21 ? 8.31E-20 100% 3.3682 16.89 ? 0.51 7.0 8.71E-16 ? 4.67E-18 2.57E-16 ? 1.06E-18 -1.7E-19 ? -1.8E-20 -2.9E-19 ? 2.6E-19 -6.10E-20 ? -8.05E-20 102% 3.4496 17.30 ? 0.48 8.0 8.60E-16 ? 2.72E-18 2.53E-16 ? 1.25E-18 6.2E-19 ? 3.9E-20 -2.7E-19 ? 3.7E-19 -2.94E-19 ? -1.02E-19 110% 3.7359 18.73 ? 0.60 9.0 2.62E-16 ? 2.41E-18 7.60E-17 ? 6.55E-19 2.0E-19 ? 3.7E-20 -3.0E-19 ? 3.8E-19 5.95E-20 ? 8.46E-20 93% 3.2063 16.08 ? 1.66 120 Irradiation filename: au5.1h.adl.ih5 %P 40Ar(*?atm) 39Ar(K) 38Ar(Cl?atm) 37Ar(Ca) 36Ar(Atm) %Rad R Age (Ma) 3.0 1.17E-15 ? 5.06E-18 3.26E-18 ? 2.13E-19 1.1E-18 ? 1.6E-19 -4.1E-20 ? 4.0E-19 3.69E-18 ? 1.08E-19 7% 24.6500 120.12 ? 163 3.3 7.90E-16 ? 3.56E-18 5.45E-17 ? 6.40E-19 8.6E-19 ? 1.3E-19 -1.9E-20 ? 4.3E-19 2.09E-18 ? 9.81E-20 22% 3.1822 15.96 ? 2.90 3.6 2.72E-16 ? 3.46E-18 5.22E-17 ? 5.08E-19 5.5E-19 ? 9.9E-20 -6.6E-19 ? 4.0E-19 3.23E-19 ? 7.71E-20 65% 3.3737 16.92 ? 2.23 4.0 5.44E-17 ? 3.00E-18 1.53E-17 ? 3.56E-19 9.2E-19 ? 2.3E-19 6.5E-19 ? 7.1E-19 7.68E-22 ? 6.47E-20 100% 3.5449 17.77 ? 6.36 4.3 5.96E-16 ? 3.01E-18 1.11E-16 ? 1.17E-18 7.7E-19 ? 8.6E-20 3.6E-19 ? 3.6E-19 7.48E-19 ? 8.56E-20 63% 3.3899 17.00 ? 1.20 4.5 1.60E-16 ? 2.79E-18 4.43E-17 ? 5.87E-19 3.4E-19 ? 8.0E-20 4.4E-20 ? 3.3E-19 -1.09E-19 ? -1.24E-19 120% 4.3303 21.69 ? 4.16 4.8 5.79E-16 ? 3.63E-18 1.50E-16 ? 6.80E-19 1.4E-19 ? 2.1E-20 -8.3E-19 ? 4.2E-19 -2.57E-20 ? -1.27E-19 101% 3.9086 19.59 ? 1.27 5.0 1.12E-14 ? 1.13E-17 3.17E-15 ? 4.85E-18 8.2E-18 ? 8.8E-20 -3.1E-19 ? 4.2E-19 2.23E-18 ? 2.01E-19 94% 3.3241 16.67 ? 0.10 5.3 1.44E-14 ? 2.14E-17 4.30E-15 ? 8.94E-18 1.1E-17 ? 7.1E-20 -5.7E-19 ? 4.0E-19 9.13E-19 ? 8.72E-20 98% 3.2771 16.44 ? 0.05 5.5 7.34E-15 ? 6.24E-18 2.20E-15 ? 4.53E-18 6.8E-18 ? 2.1E-19 -2.7E-20 ? 4.2E-19 1.18E-20 ? 1.33E-19 100% 3.3338 16.72 ? 0.10 5.8 1.67E-15 ? 4.45E-18 4.96E-16 ? 1.83E-18 1.8E-18 ? 1.2E-19 -4.0E-19 ? 3.6E-19 2.61E-19 ? 8.58E-20 95% 3.2087 16.10 ? 0.27 6.0 2.36E-15 ? 3.54E-18 7.08E-16 ? 2.51E-18 1.1E-18 ? 5.3E-20 -6.7E-19 ? 3.4E-19 1.87E-19 ? 8.74E-20 98% 3.2571 16.34 ? 0.19 6.5 2.13E-16 ? 2.32E-18 6.26E-17 ? 4.90E-19 3.7E-19 ? 7.8E-20 6.9E-19 ? 3.9E-19 2.44E-19 ? 1.33E-19 66% 2.2546 11.33 ? 3.16 7.0 1.45E-17 ? 1.81E-18 3.81E-18 ? 2.93E-19 1.4E-19 ? 1.6E-19 2.1E-19 ? 3.5E-19 3.56E-19 ? 1.32E-19 -623% -23.7740 -123.96 ? -54 8.0 1.55E-17 ? 1.46E-18 2.93E-18 ? 2.82E-19 1.7E-19 ? 1.7E-19 2.6E-19 ? 3.4E-19 -1.23E-19 ? -1.69E-19 334% 17.7467 87.28 ? 83 9.0 7.61E-18 ? 1.68E-18 1.08E-18 ? 3.78E-19 5.8E-20 ? 1.9E-19 2.6E-19 ? 3.5E-19 3.17E-19 ? 1.35E-19 -1131% -79.9909 -456.17 ? -274 10.0 5.54E-18 ? 2.32E-18 2.07E-19 ? 3.26E-19 8.8E-20 ? 1.8E-19 9.6E-19 ? 3.5E-19 -1.28E-19 ? -1.68E-19 780% 209.5503 831.25 ? 1487 121 Oro Fino deposit step heating increments for 5 single adularia crystals (14-20, 1.2-0.75 mm) of sample: OF-1 Irradiation filename:au8.adl.31 %P 40Ar(*?atm) 39Ar(K) 38Ar(Cl?atm) 37Ar(Ca) 36Ar(Atm) %Rad R Age (Ma) 6.0 1.43E-14 ? 4.23E-17 8.16E-16 ? 2.96E-18 8.8E-18 ? 1.4E-19 -4.9E-19 ? 8.2E-19 3.47E-17 ? 4.91E-19 28% 4.9117 17.17 ? 0.70 6.5 8.58E-15 ? 1.85E-17 1.76E-15 ? 3.81E-18 5.0E-18 ? 1.0E-19 1.0E-19 ? 8.5E-19 1.45E-18 ? 7.08E-20 95% 4.6209 16.16 ? 0.07 7.0 6.97E-15 ? 6.66E-18 1.41E-15 ? 5.14E-18 4.1E-18 ? 6.7E-20 6.0E-20 ? 7.5E-19 1.01E-18 ? 1.19E-19 96% 4.7254 16.52 ? 0.11 7.5 2.73E-15 ? 3.27E-18 5.38E-16 ? 1.33E-18 1.9E-18 ? 5.2E-20 1.4E-18 ? 1.0E-18 5.91E-19 ? 8.24E-20 94% 4.7521 16.61 ? 0.17 8.0 4.47E-15 ? 4.10E-18 7.27E-16 ? 2.75E-18 2.6E-18 ? 6.3E-20 -4.6E-19 ? 7.8E-19 3.61E-18 ? 9.50E-20 76% 4.6754 16.35 ? 0.16 8.5 2.25E-15 ? 6.62E-18 3.86E-16 ? 1.71E-18 1.3E-18 ? 4.6E-20 -7.2E-19 ? 9.6E-19 1.53E-18 ? 8.22E-20 80% 4.6679 16.32 ? 0.25 9.0 3.04E-15 ? 4.77E-18 5.40E-16 ? 3.33E-18 1.4E-18 ? 3.3E-20 -5.8E-19 ? 1.1E-18 1.70E-18 ? 8.42E-20 83% 4.6990 16.43 ? 0.21 9.3 5.32E-15 ? 7.19E-18 1.01E-15 ? 2.09E-18 2.9E-18 ? 5.3E-20 -2.1E-19 ? 9.6E-19 2.04E-18 ? 9.68E-20 89% 4.6827 16.37 ? 0.11 9.5 4.35E-15 ? 8.66E-18 8.81E-16 ? 1.79E-18 2.1E-18 ? 4.0E-20 -3.2E-19 ? 1.1E-18 8.00E-19 ? 7.69E-20 95% 4.6648 16.31 ? 0.10 9.8 4.85E-15 ? 1.11E-17 9.89E-16 ? 3.58E-18 2.1E-18 ? 5.1E-20 -9.1E-19 ? 9.8E-19 7.29E-19 ? 6.69E-20 96% 4.6841 16.38 ? 0.10 10.0 2.97E-15 ? 3.40E-18 6.21E-16 ? 2.45E-18 1.6E-18 ? 4.2E-20 -1.9E-18 ? 7.1E-19 2.38E-19 ? 5.95E-20 98% 4.6756 16.35 ? 0.12 10.3 9.17E-15 ? 9.00E-18 1.90E-15 ? 4.32E-18 4.6E-18 ? 8.2E-20 -9.5E-19 ? 7.2E-19 1.03E-18 ? 5.98E-20 97% 4.6697 16.33 ? 0.05 10.5 3.70E-15 ? 2.71E-18 7.78E-16 ? 1.80E-18 1.7E-18 ? 2.7E-20 -8.5E-19 ? 7.0E-19 2.37E-19 ? 6.24E-20 98% 4.6607 16.29 ? 0.09 11.0 1.09E-15 ? 3.04E-18 2.31E-16 ? 1.12E-18 2.3E-19 ? 1.5E-20 -8.5E-19 ? 7.5E-19 1.41E-19 ? 6.40E-20 96% 4.5295 15.84 ? 0.30 11.5 5.76E-16 ? 2.94E-18 1.20E-16 ? 6.27E-19 3.5E-19 ? 3.6E-20 -1.2E-18 ? 7.9E-19 -1.12E-19 ? -1.01E-19 106% 5.0730 17.73 ? 0.88 12.5 2.39E-16 ? 2.62E-18 4.94E-17 ? 4.52E-19 1.3E-19 ? 3.8E-20 1.8E-19 ? 6.7E-19 -1.29E-20 ? -6.99E-20 102% 4.9217 17.20 ? 1.48 13.5 1.85E-16 ? 2.64E-18 3.76E-17 ? 3.87E-19 6.5E-20 ? 2.3E-20 2.5E-19 ? 3.7E-19 -1.82E-19 ? -1.08E-19 129% 6.3528 22.17 ? 2.97 122 Irradiation filename:au8.adl.32 %P 40Ar(*?atm) 39Ar(K) 38Ar(Cl?atm) 37Ar(Ca) 36Ar(Atm) %Rad R Age (Ma) 5.0 2.57E-14 ? 1.39E-17 5.54E-17 ? 8.61E-19 1.7E-17 ? 2.9E-19 5.1E-19 ? 5.5E-19 8.50E-17 ? 3.52E-19 2% 10.8934 37.86 ? 35 6.0 8.06E-15 ? 9.79E-18 6.86E-16 ? 2.12E-18 4.6E-18 ? 1.3E-19 2.7E-18 ? 8.3E-19 1.57E-17 ? 1.20E-19 42% 4.9821 17.41 ? 0.24 6.3 3.19E-15 ? 3.13E-18 6.27E-16 ? 1.80E-18 1.7E-18 ? 3.3E-20 1.0E-19 ? 4.0E-19 8.43E-19 ? 7.59E-20 92% 4.6891 16.39 ? 0.14 6.7 6.30E-15 ? 7.11E-18 1.15E-15 ? 3.92E-18 3.2E-18 ? 7.5E-20 -6.8E-20 ? 5.6E-19 3.45E-18 ? 1.60E-19 84% 4.5819 16.02 ? 0.16 7.0 6.26E-15 ? 5.09E-18 1.30E-15 ? 3.41E-18 3.4E-18 ? 5.2E-20 8.3E-20 ? 4.7E-19 8.59E-19 ? 7.17E-20 96% 4.6184 16.15 ? 0.07 7.5 1.92E-14 ? 2.16E-17 2.85E-15 ? 6.81E-18 1.1E-17 ? 9.7E-20 1.5E-18 ? 5.7E-19 2.03E-17 ? 1.59E-19 69% 4.6478 16.25 ? 0.09 8.0 7.55E-15 ? 1.40E-17 1.35E-15 ? 3.78E-18 3.5E-18 ? 6.4E-20 1.2E-18 ? 6.6E-19 4.54E-18 ? 9.00E-20 82% 4.6099 16.12 ? 0.10 8.5 1.07E-14 ? 1.29E-17 1.77E-15 ? 7.71E-18 5.2E-18 ? 8.0E-20 -7.9E-19 ? 7.9E-19 8.31E-18 ? 1.12E-19 77% 4.6515 16.26 ? 0.12 9.0 1.01E-14 ? 1.35E-17 1.86E-15 ? 4.43E-18 5.3E-18 ? 4.5E-20 -6.1E-19 ? 7.1E-19 4.75E-18 ? 1.04E-19 86% 4.6770 16.35 ? 0.08 9.3 8.16E-15 ? 9.36E-18 1.53E-15 ? 3.92E-18 4.2E-18 ? 9.0E-20 -1.2E-18 ? 8.3E-19 3.25E-18 ? 8.58E-20 88% 4.6910 16.40 ? 0.08 9.5 4.26E-15 ? 2.68E-18 8.13E-16 ? 1.85E-18 2.0E-18 ? 5.5E-20 -1.1E-18 ? 8.8E-19 1.54E-18 ? 8.50E-20 89% 4.6721 16.33 ? 0.12 9.7 3.97E-15 ? 3.74E-18 7.55E-16 ? 3.52E-18 2.3E-18 ? 5.2E-20 -1.5E-18 ? 6.6E-19 1.57E-18 ? 9.19E-20 88% 4.6360 16.21 ? 0.15 10.0 6.18E-15 ? 9.83E-18 1.20E-15 ? 2.07E-18 3.1E-18 ? 6.9E-20 -5.6E-19 ? 9.1E-19 1.95E-18 ? 7.29E-20 91% 4.6829 16.37 ? 0.08 10.2 1.00E-14 ? 1.00E-17 1.98E-15 ? 5.30E-18 5.2E-18 ? 6.1E-20 -1.2E-18 ? 7.9E-19 2.63E-18 ? 6.62E-20 92% 4.6640 16.31 ? 0.06 10.5 9.67E-15 ? 4.95E-18 1.79E-15 ? 3.14E-18 4.9E-18 ? 6.0E-20 -1.2E-18 ? 7.1E-19 4.20E-18 ? 1.07E-19 87% 4.6966 16.42 ? 0.07 11.0 3.89E-15 ? 3.90E-18 7.94E-16 ? 2.10E-18 1.9E-18 ? 4.5E-20 1.0E-18 ? 9.0E-19 6.95E-19 ? 8.21E-20 95% 4.6360 16.21 ? 0.12 11.5 1.31E-15 ? 4.21E-18 2.74E-16 ? 1.03E-18 9.8E-19 ? 4.7E-20 -8.0E-19 ? 7.1E-19 1.81E-19 ? 6.86E-20 96% 4.5959 16.07 ? 0.27 12.5 1.25E-15 ? 3.06E-18 2.48E-16 ? 1.19E-18 7.1E-19 ? 3.7E-20 -4.2E-19 ? 1.1E-18 2.49E-19 ? 8.68E-20 94% 4.7585 16.63 ? 0.37 13.5 1.18E-16 ? 2.43E-18 2.41E-17 ? 5.46E-19 5.6E-20 ? 3.7E-20 3.1E-19 ? 1.1E-18 7.51E-20 ? 7.60E-20 81% 3.9678 13.88 ? 3.31 15.0 6.00E-17 ? 2.65E-18 1.25E-17 ? 5.47E-19 3.9E-19 ? 1.4E-19 -5.9E-19 ? 1.0E-18 -2.28E-19 ? -1.15E-19 212% 10.2384 35.60 ? 9.56 17.0 2.25E-17 ? 2.32E-18 5.45E-18 ? 5.51E-19 -1.5E-19 ? -3.4E-19 2.0E-18 ? 8.5E-19 -2.25E-19 ? -1.15E-19 395% 16.3227 56.43 ? 22 123 Irradiation filename:au8.adl.33 %P 40Ar(*?atm) 39Ar(K) 38Ar(Cl?atm) 37Ar(Ca) 36Ar(Atm) %Rad R Age (Ma) 5.0 1.77E-14 ? 1.73E-17 4.94E-16 ? 6.43E-19 1.1E-17 ? 2.0E-19 -2.6E-19 ? 6.8E-19 5.08E-17 ? 3.28E-19 15% 5.4937 19.19 ? 0.73 6.0 7.37E-15 ? 2.13E-17 1.51E-15 ? 5.95E-18 3.7E-18 ? 9.2E-20 3.3E-19 ? 6.8E-19 1.43E-18 ? 7.66E-20 94% 4.6136 16.13 ? 0.10 6.3 4.98E-15 ? 1.11E-17 9.36E-16 ? 1.22E-18 2.4E-18 ? 7.3E-20 4.7E-20 ? 4.6E-19 2.11E-18 ? 9.85E-20 87% 4.6494 16.25 ? 0.12 6.7 7.54E-15 ? 4.90E-18 1.37E-15 ? 3.17E-18 4.2E-18 ? 6.7E-20 2.5E-18 ? 1.0E-18 4.04E-18 ? 8.53E-20 84% 4.6385 16.22 ? 0.08 7.0 5.04E-15 ? 4.05E-18 8.90E-16 ? 2.66E-18 2.7E-18 ? 7.1E-20 2.4E-18 ? 9.9E-19 3.17E-18 ? 7.14E-20 81% 4.6094 16.12 ? 0.10 7.5 2.04E-14 ? 1.80E-17 3.51E-15 ? 1.11E-17 1.1E-17 ? 8.9E-20 5.5E-18 ? 1.5E-18 1.41E-17 ? 1.40E-19 80% 4.6347 16.20 ? 0.08 8.0 2.68E-15 ? 4.32E-18 4.56E-16 ? 1.32E-18 1.3E-18 ? 4.2E-20 3.3E-18 ? 1.0E-18 1.88E-18 ? 7.77E-20 79% 4.6644 16.31 ? 0.19 8.5 1.35E-14 ? 7.00E-18 2.29E-15 ? 3.35E-18 7.7E-18 ? 1.2E-19 6.9E-19 ? 6.7E-19 9.53E-18 ? 1.48E-19 79% 4.6565 16.28 ? 0.07 9.0 4.23E-15 ? 1.57E-17 7.27E-16 ? 2.09E-18 2.3E-18 ? 6.7E-20 5.3E-19 ? 5.7E-19 2.91E-18 ? 1.20E-19 80% 4.6356 16.21 ? 0.20 9.3 1.79E-15 ? 3.18E-18 3.22E-16 ? 8.50E-19 8.7E-19 ? 3.8E-20 -3.9E-19 ? 7.9E-19 1.23E-18 ? 1.18E-19 80% 4.4158 15.44 ? 0.38 9.5 1.68E-15 ? 3.90E-18 3.03E-16 ? 1.38E-18 6.5E-19 ? 3.4E-20 5.6E-19 ? 7.8E-19 1.23E-18 ? 1.10E-19 78% 4.3458 15.20 ? 0.39 9.7 5.42E-16 ? 4.09E-18 9.67E-17 ? 5.69E-19 2.0E-19 ? 2.7E-20 4.3E-19 ? 6.2E-19 6.48E-19 ? 1.07E-19 65% 3.6213 12.67 ? 1.16 10.0 1.28E-16 ? 1.62E-18 2.00E-17 ? 4.43E-19 -1.7E-19 ? -1.4E-18 6.7E-19 ? 8.3E-19 3.02E-19 ? 9.60E-20 30% 1.9513 6.84 ? 5.03 124 Irradiation filename:au8.adl.34 %P 40Ar(*?atm) 39Ar(K) 38Ar(Cl?atm) 37Ar(Ca) 36Ar(Atm) %Rad R Age (Ma) 5.0 1.46E-14 ? 9.17E-18 3.53E-16 ? 7.64E-19 9.3E-18 ? 1.4E-19 -6.5E-19 ? 8.2E-19 4.23E-17 ? 2.40E-19 14% 5.8679 20.49 ? 0.82 6.0 4.03E-15 ? 3.63E-18 6.91E-16 ? 2.67E-18 2.5E-18 ? 6.8E-20 5.0E-19 ? 7.2E-19 2.74E-18 ? 8.27E-20 80% 4.6647 16.31 ? 0.15 6.3 2.24E-15 ? 5.19E-18 4.53E-16 ? 1.26E-18 1.3E-18 ? 6.6E-20 4.3E-19 ? 8.2E-19 5.44E-19 ? 8.11E-20 93% 4.5904 16.05 ? 0.20 6.7 3.73E-15 ? 3.65E-18 7.93E-16 ? 2.13E-18 8.0E-19 ? 2.8E-20 2.6E-19 ? 7.0E-19 4.41E-19 ? 8.24E-20 97% 4.5323 15.85 ? 0.12 7.0 2.64E-15 ? 4.70E-18 5.40E-16 ? 8.78E-19 9.1E-19 ? 4.4E-20 1.2E-18 ? 9.9E-19 4.63E-19 ? 8.13E-20 95% 4.6294 16.19 ? 0.16 7.5 7.93E-15 ? 1.04E-17 1.55E-15 ? 3.94E-18 2.6E-18 ? 8.3E-20 1.2E-18 ? 1.1E-18 2.70E-18 ? 1.03E-19 90% 4.6074 16.11 ? 0.09 8.0 1.51E-14 ? 1.87E-17 2.55E-15 ? 4.16E-18 8.1E-18 ? 9.5E-20 3.7E-18 ? 1.1E-18 1.16E-17 ? 1.26E-19 77% 4.5747 15.99 ? 0.07 8.5 2.17E-15 ? 6.89E-18 2.58E-16 ? 1.28E-18 1.1E-18 ? 7.7E-20 1.5E-19 ? 1.1E-18 3.28E-18 ? 1.37E-19 55% 4.6727 16.34 ? 0.58 9.0 6.22E-15 ? 1.05E-17 8.65E-16 ? 3.17E-18 3.1E-18 ? 4.8E-20 -3.7E-19 ? 8.3E-19 7.49E-18 ? 1.48E-19 64% 4.6298 16.19 ? 0.21 9.3 3.31E-15 ? 2.98E-18 4.90E-16 ? 1.33E-18 1.3E-18 ? 3.8E-20 8.8E-19 ? 7.7E-19 3.56E-18 ? 1.37E-19 68% 4.6128 16.13 ? 0.30 9.5 1.82E-15 ? 5.82E-18 2.66E-16 ? 7.82E-19 9.4E-19 ? 5.9E-20 6.5E-20 ? 7.1E-19 2.17E-18 ? 1.28E-19 65% 4.4091 15.42 ? 0.51 9.7 5.65E-16 ? 3.64E-18 7.83E-17 ? 6.80E-19 1.4E-19 ? 3.0E-20 5.0E-19 ? 8.1E-19 7.87E-19 ? 1.28E-19 59% 4.2381 14.82 ? 1.71 10.0 2.31E-15 ? 7.42E-18 3.55E-16 ? 6.94E-19 1.1E-18 ? 4.0E-20 5.3E-19 ? 7.4E-19 1.99E-18 ? 1.53E-19 75% 4.8465 16.94 ? 0.45 10.2 2.54E-15 ? 6.05E-18 3.54E-16 ? 1.30E-18 1.5E-18 ? 5.3E-20 -5.3E-20 ? 5.3E-19 3.04E-18 ? 7.14E-20 65% 4.6401 16.22 ? 0.24 10.5 8.60E-16 ? 3.22E-18 1.31E-16 ? 8.32E-19 2.3E-19 ? 3.2E-20 8.8E-20 ? 6.9E-19 8.17E-19 ? 7.18E-20 72% 4.7411 16.57 ? 0.59 11.0 2.63E-15 ? 2.94E-18 4.27E-16 ? 1.19E-18 1.1E-18 ? 3.8E-20 3.5E-19 ? 8.6E-19 2.19E-18 ? 8.31E-20 75% 4.6427 16.23 ? 0.21 11.5 5.29E-15 ? 3.95E-18 8.83E-16 ? 2.99E-18 2.9E-18 ? 3.3E-20 -2.2E-18 ? 1.1E-18 3.79E-18 ? 1.07E-19 79% 4.7121 16.47 ? 0.15 12.5 3.87E-15 ? 3.50E-18 6.49E-16 ? 2.29E-18 1.9E-18 ? 5.6E-20 1.7E-19 ? 6.8E-19 2.97E-18 ? 1.60E-19 77% 4.6095 16.12 ? 0.27 13.5 3.03E-15 ? 2.12E-18 5.20E-16 ? 1.54E-18 9.6E-19 ? 3.1E-20 -1.8E-20 ? 6.9E-19 2.25E-18 ? 1.16E-19 78% 4.5401 15.87 ? 0.24 15.0 5.25E-16 ? 1.95E-18 7.99E-17 ? 6.37E-19 1.6E-19 ? 2.4E-20 1.6E-19 ? 6.3E-19 7.48E-19 ? 1.13E-19 58% 3.8094 13.33 ? 1.48 17.0 4.25E-17 ? 1.86E-18 7.01E-18 ? 3.90E-19 -2.2E-19 ? -2.3E-19 -4.6E-19 ? 8.2E-19 2.28E-19 ? 1.38E-19 -59% -3.5524 -12.52 ? -20 125 Irradiation filename:au8.adl.35 %P 40Ar(*?atm) 39Ar(K) 38Ar(Cl?atm) 37Ar(Ca) 36Ar(Atm) %Rad R Age (Ma) 5.0 2.10E-14 ? 3.78E-17 1.34E-15 ? 1.76E-18 1.5E-17 ? 2.4E-19 1.8E-19 ? 6.4E-19 5.06E-17 ? 5.02E-19 29% 4.5522 15.92 ? 0.41 6.0 1.26E-14 ? 1.70E-17 2.50E-15 ? 6.53E-18 7.5E-18 ? 7.3E-20 1.4E-19 ? 6.3E-19 3.68E-18 ? 8.69E-20 91% 4.5951 16.07 ? 0.06 6.3 2.32E-15 ? 6.93E-18 3.84E-16 ? 9.54E-19 1.9E-18 ? 7.4E-20 -2.5E-19 ? 6.7E-19 1.86E-18 ? 8.40E-20 76% 4.6159 16.14 ? 0.24 6.7 5.93E-15 ? 2.86E-18 9.62E-16 ? 2.26E-18 3.0E-18 ? 3.3E-20 2.2E-18 ? 1.3E-18 5.11E-18 ? 1.45E-19 75% 4.5915 16.05 ? 0.16 7.0 5.87E-15 ? 7.25E-18 1.13E-15 ? 3.27E-18 2.4E-18 ? 4.1E-20 -9.2E-19 ? 8.3E-19 2.38E-18 ? 1.40E-19 88% 4.5865 16.04 ? 0.14 7.5 7.85E-15 ? 9.05E-18 1.49E-15 ? 1.64E-18 4.1E-18 ? 5.4E-20 -1.3E-18 ? 7.7E-19 3.42E-18 ? 1.39E-19 87% 4.5853 16.03 ? 0.10 8.0 4.02E-15 ? 2.62E-18 7.78E-16 ? 2.18E-18 2.0E-18 ? 4.7E-20 1.4E-18 ? 7.2E-19 1.43E-18 ? 8.79E-20 89% 4.6167 16.14 ? 0.13 8.5 2.81E-15 ? 7.74E-18 5.72E-16 ? 3.17E-18 1.5E-18 ? 5.3E-20 1.3E-18 ? 8.0E-19 6.01E-19 ? 6.48E-20 94% 4.5999 16.08 ? 0.16 9.0 2.34E-15 ? 3.54E-18 4.45E-16 ? 1.40E-18 1.1E-18 ? 5.1E-20 9.9E-19 ? 7.6E-19 8.58E-19 ? 8.59E-20 89% 4.7009 16.43 ? 0.21 9.3 8.79E-16 ? 2.13E-18 1.79E-16 ? 1.08E-18 5.2E-19 ? 4.2E-20 3.6E-18 ? 1.4E-18 1.50E-19 ? 7.34E-20 95% 4.6617 16.30 ? 0.44 9.5 3.60E-16 ? 3.07E-18 7.07E-17 ? 6.31E-19 3.0E-19 ? 4.4E-20 8.7E-19 ? 7.6E-19 1.31E-19 ? 6.51E-20 89% 4.5417 15.88 ? 0.98 9.7 7.71E-17 ? 2.53E-18 1.54E-17 ? 2.76E-19 2.9E-19 ? 1.1E-19 1.0E-18 ? 7.5E-19 -1.05E-19 ? -1.09E-19 140% 7.0162 24.47 ? 7.32 126 War Eagle Mountain site 3 deposit step heating increments for 5 single crystals (14-20 mesh size, 1.2-0.75 mm) of sample: WEMS3-1 Irradiation filename: au8.2c.adl.41. %P 40Ar(*?atm) 39Ar(K) 38Ar(Cl?atm) 37Ar(Ca) 36Ar(Atm) %Rad R Age (Ma) 6.00 7.53E-15 ? 9.52E-18 5.40E-17 ? 9.45E-19 4.6E-18 ? 1.7E-19 -1.1E-18 ? 1.2E-18 2.45E-17 ? 2.13E-19 4% 5.5793 19.49 ? 12 6.50 2.87E-15 ? 5.27E-18 4.44E-16 ? 9.84E-19 8.8E-19 ? 3.3E-20 -1.7E-18 ? 7.3E-19 3.06E-18 ? 1.06E-19 68% 4.4193 15.45 ? 0.26 7.00 2.26E-16 ? 2.17E-18 4.14E-17 ? 4.35E-19 9.2E-20 ? 2.7E-20 -3.0E-18 ? 1.5E-18 1.71E-19 ? 8.30E-20 78% 4.2256 14.78 ? 2.09 7.50 1.42E-15 ? 2.44E-18 3.09E-16 ? 1.58E-18 8.2E-19 ? 3.5E-20 -5.3E-20 ? 6.5E-19 1.51E-19 ? 6.23E-20 97% 4.4426 15.53 ? 0.23 8.00 1.31E-15 ? 6.16E-18 2.87E-16 ? 1.93E-18 8.1E-19 ? 5.1E-20 -2.4E-19 ? 7.7E-19 3.24E-19 ? 6.65E-20 93% 4.2443 14.84 ? 0.27 8.50 1.87E-14 ? 1.24E-17 3.29E-15 ? 5.47E-18 1.0E-17 ? 6.4E-20 7.4E-19 ? 8.3E-19 1.38E-17 ? 1.57E-19 78% 4.4271 15.48 ? 0.06 9.00 1.49E-14 ? 2.33E-17 2.50E-15 ? 4.89E-18 8.1E-18 ? 7.6E-20 -1.0E-19 ? 7.8E-19 1.24E-17 ? 1.17E-19 75% 4.4789 15.66 ? 0.07 9.25 3.24E-15 ? 2.31E-18 5.81E-16 ? 1.68E-18 1.6E-18 ? 7.2E-20 -6.5E-19 ? 6.7E-19 2.39E-18 ? 1.21E-19 78% 4.3512 15.22 ? 0.22 9.50 6.15E-15 ? 9.56E-18 1.15E-15 ? 2.71E-18 2.8E-18 ? 4.6E-20 -4.1E-19 ? 7.2E-19 3.47E-18 ? 1.29E-19 83% 4.4664 15.62 ? 0.13 9.75 4.65E-15 ? 4.07E-18 9.14E-16 ? 2.71E-18 2.5E-18 ? 5.6E-20 -1.6E-18 ? 9.8E-19 1.89E-18 ? 1.65E-19 88% 4.4782 15.66 ? 0.19 10.00 2.69E-15 ? 4.19E-18 5.32E-16 ? 1.11E-18 1.0E-18 ? 4.0E-20 -8.2E-19 ? 5.4E-19 1.11E-18 ? 1.72E-19 88% 4.4315 15.50 ? 0.34 10.25 1.23E-15 ? 6.14E-18 2.48E-16 ? 8.71E-19 3.0E-20 ? 2.8E-21 -3.3E-19 ? 6.8E-19 3.48E-19 ? 9.18E-20 92% 4.5200 15.80 ? 0.40 10.50 5.95E-15 ? 8.19E-18 1.10E-15 ? 5.48E-18 3.3E-18 ? 5.8E-20 6.6E-19 ? 9.6E-19 3.59E-18 ? 9.73E-20 82% 4.4411 15.53 ? 0.13 11.00 3.58E-15 ? 6.87E-18 6.66E-16 ? 2.79E-18 1.9E-18 ? 5.7E-20 4.2E-19 ? 8.3E-19 1.98E-18 ? 8.80E-20 84% 4.4853 15.68 ? 0.16 11.50 5.06E-16 ? 2.67E-18 9.35E-17 ? 5.36E-19 2.8E-19 ? 4.3E-20 -1.7E-19 ? 7.0E-19 3.00E-19 ? 7.51E-20 83% 4.4666 15.62 ? 0.84 12.50 1.56E-16 ? 1.83E-18 2.97E-17 ? 4.58E-19 3.4E-19 ? 1.2E-19 -1.8E-18 ? 1.2E-18 -2.29E-19 ? -1.24E-19 143% 7.5409 26.29 ? 4.32 13.50 3.57E-17 ? 1.30E-18 5.77E-18 ? 6.80E-19 2.9E-19 ? 1.2E-19 -6.5E-20 ? 7.4E-19 2.32E-20 ? 7.66E-20 81% 4.9959 17.46 ? 13 15.00 1.65E-16 ? 2.92E-18 3.14E-17 ? 3.68E-19 1.2E-19 ? 3.9E-20 3.4E-19 ? 6.6E-19 7.83E-20 ? 1.84E-19 86% 4.5313 15.84 ? 6.08 17.00 1.55E-16 ? 1.46E-18 1.73E-17 ? 2.56E-19 1.3E-19 ? 7.1E-20 -1.5E-18 ? 5.8E-19 4.14E-19 ? 1.95E-19 21% 1.8704 6.56 ? 11 20.00 5.35E-17 ? 1.46E-18 7.70E-18 ? 1.97E-19 2.2E-20 ? 3.5E-20 1.6E-18 ? 6.9E-19 4.40E-19 ? 1.77E-19 -143% -9.9315 -35.22 ? -24 24.00 1.04E-16 ? 2.23E-18 1.23E-17 ? 3.87E-19 2.4E-19 ? 1.2E-19 1.1E-18 ? 4.8E-19 2.82E-19 ? 1.97E-19 20% 1.7384 6.09 ? 16 127 Irradiation filename: au8.2c.adl.42. %P 40Ar(*?atm) 39Ar(K) 38Ar(Cl?atm) 37Ar(Ca) 36Ar(Atm) %Rad R Age (Ma) 6.00 2.69E-15 ? 3.66E-18 9.49E-17 ? 4.85E-19 1.3E-18 ? 1.3E-19 -7.1E-19 ? 8.1E-19 7.85E-18 ? 1.61E-19 14% 3.8536 13.48 ? 1.89 6.50 7.77E-15 ? 6.86E-18 1.56E-15 ? 3.15E-18 3.7E-18 ? 4.4E-20 2.6E-18 ? 1.2E-18 2.62E-18 ? 1.46E-19 90% 4.4808 15.67 ? 0.10 7.00 5.28E-15 ? 6.07E-18 1.14E-15 ? 3.14E-18 2.8E-18 ? 5.1E-20 -2.2E-19 ? 6.4E-19 8.52E-19 ? 1.41E-19 95% 4.4157 15.44 ? 0.14 7.50 3.83E-15 ? 2.50E-18 8.06E-16 ? 1.89E-18 2.4E-18 ? 5.6E-20 6.8E-20 ? 4.6E-19 9.33E-19 ? 1.31E-19 93% 4.4098 15.42 ? 0.17 8.00 4.45E-15 ? 3.86E-18 9.19E-16 ? 1.80E-18 2.5E-18 ? 5.1E-20 5.2E-19 ? 6.2E-19 1.14E-18 ? 1.34E-19 92% 4.4751 15.65 ? 0.16 8.50 1.16E-14 ? 1.11E-17 2.40E-15 ? 3.60E-18 5.7E-18 ? 6.8E-20 9.8E-19 ? 4.9E-19 2.84E-18 ? 1.48E-19 93% 4.4837 15.68 ? 0.07 9.00 1.58E-14 ? 1.81E-17 3.16E-15 ? 4.78E-18 7.5E-18 ? 5.6E-20 1.4E-18 ? 6.7E-19 5.59E-18 ? 1.52E-19 90% 4.4695 15.63 ? 0.06 9.25 7.80E-15 ? 5.74E-18 1.48E-15 ? 5.08E-18 4.2E-18 ? 3.4E-20 -4.2E-20 ? 7.6E-19 3.84E-18 ? 9.26E-20 85% 4.5072 15.76 ? 0.09 9.50 3.50E-15 ? 6.81E-18 6.85E-16 ? 1.61E-18 1.6E-18 ? 2.9E-20 -1.4E-18 ? 7.3E-19 1.44E-18 ? 9.08E-20 88% 4.4860 15.69 ? 0.15 9.75 1.29E-15 ? 4.07E-18 2.33E-16 ? 9.26E-19 6.3E-19 ? 2.9E-20 -2.0E-19 ? 7.9E-19 7.66E-19 ? 8.33E-20 82% 4.5584 15.94 ? 0.38 10.00 2.71E-15 ? 4.94E-18 4.64E-16 ? 1.67E-18 1.3E-18 ? 5.7E-20 4.9E-21 ? 6.9E-19 2.04E-18 ? 9.86E-20 78% 4.5440 15.89 ? 0.23 10.25 4.44E-16 ? 3.28E-18 8.05E-17 ? 7.98E-19 2.3E-19 ? 2.8E-20 -7.1E-20 ? 8.7E-19 2.05E-19 ? 7.54E-20 86% 4.7558 16.62 ? 1.00 10.50 7.99E-16 ? 5.14E-18 1.34E-16 ? 5.33E-19 6.3E-19 ? 6.3E-20 -3.3E-19 ? 7.3E-19 7.75E-19 ? 7.95E-20 71% 4.2638 14.91 ? 0.64 11.00 3.17E-15 ? 4.67E-18 5.01E-16 ? 2.88E-18 1.8E-18 ? 3.9E-20 5.4E-20 ? 8.3E-19 2.97E-18 ? 9.19E-20 72% 4.5651 15.96 ? 0.23 11.50 1.23E-15 ? 4.39E-18 2.24E-16 ? 9.13E-19 6.5E-19 ? 5.4E-20 -1.0E-18 ? 8.1E-19 7.45E-19 ? 8.46E-20 82% 4.4799 15.66 ? 0.40 12.50 2.84E-15 ? 3.18E-18 5.04E-16 ? 5.61E-19 2.0E-18 ? 7.0E-20 1.1E-18 ? 7.5E-19 1.83E-18 ? 9.84E-20 81% 4.5538 15.92 ? 0.20 13.50 3.75E-15 ? 3.87E-18 6.85E-16 ? 1.33E-18 2.5E-18 ? 6.5E-20 1.1E-18 ? 8.8E-19 2.07E-18 ? 1.00E-19 84% 4.5714 15.98 ? 0.16 15.00 1.58E-15 ? 4.74E-18 3.03E-16 ? 1.39E-18 1.0E-18 ? 4.9E-20 -6.1E-19 ? 7.7E-19 8.39E-19 ? 7.54E-20 84% 4.4009 15.39 ? 0.28 17.00 3.21E-15 ? 3.20E-18 5.95E-16 ? 1.21E-18 1.8E-18 ? 5.4E-20 -1.9E-19 ? 7.2E-19 1.76E-18 ? 9.72E-20 84% 4.5120 15.78 ? 0.17 20.00 8.65E-16 ? 4.27E-18 1.54E-16 ? 5.83E-19 2.8E-19 ? 3.0E-20 -2.9E-19 ? 8.0E-19 9.22E-19 ? 7.82E-20 69% 3.8405 13.44 ? 0.54 24.00 7.57E-16 ? 2.82E-18 1.49E-16 ? 7.32E-19 3.1E-19 ? 3.3E-20 -1.4E-18 ? 7.1E-19 4.39E-19 ? 8.18E-20 83% 4.1926 14.66 ? 0.58 128 Irradiation filename: au8.2c.adl.43. %P 40Ar(*?atm) 39Ar(K) 38Ar(Cl?atm) 37Ar(Ca) 36Ar(Atm) %Rad R Age (Ma) 6.00 2.69E-15 ? 3.66E-18 9.49E-17 ? 4.85E-19 1.3E-18 ? 1.3E-19 -7.1E-19 ? 8.1E-19 7.85E-18 ? 1.61E-19 14% 3.8536 13.48 ? 1.89 6.50 5.53E-15 ? 7.68E-18 1.21E-15 ? 4.27E-18 3.0E-18 ? 5.7E-20 -2.6E-18 ? 1.6E-18 4.64E-19 ? 8.57E-20 98% 4.4452 15.54 ? 0.09 7.00 8.18E-15 ? 8.28E-18 1.74E-15 ? 4.37E-18 4.6E-18 ? 7.5E-20 1.6E-18 ? 9.3E-19 1.57E-18 ? 7.87E-20 94% 4.4292 15.49 ? 0.06 7.50 5.16E-15 ? 5.60E-18 1.02E-15 ? 3.98E-18 2.4E-18 ? 4.8E-20 1.4E-18 ? 1.1E-18 2.17E-18 ? 8.41E-20 88% 4.4305 15.49 ? 0.11 8.00 1.95E-15 ? 4.75E-18 4.00E-16 ? 1.47E-18 9.6E-19 ? 3.7E-20 -5.7E-19 ? 1.0E-18 5.96E-19 ? 7.84E-20 91% 4.4264 15.48 ? 0.22 8.50 7.08E-15 ? 5.67E-18 1.23E-15 ? 1.94E-18 3.8E-18 ? 6.8E-20 -5.6E-19 ? 1.0E-18 5.04E-18 ? 9.45E-20 79% 4.5218 15.81 ? 0.09 9.00 6.60E-15 ? 9.80E-18 1.38E-15 ? 3.57E-18 3.1E-18 ? 3.7E-20 -5.8E-19 ? 8.2E-19 1.41E-18 ? 1.31E-19 94% 4.4723 15.64 ? 0.11 9.25 1.81E-15 ? 4.06E-18 3.77E-16 ? 1.14E-18 1.0E-18 ? 4.2E-20 -6.3E-19 ? 9.4E-19 5.82E-19 ? 1.17E-19 91% 4.3498 15.21 ? 0.33 9.50 4.40E-15 ? 5.57E-18 8.92E-16 ? 1.87E-18 1.9E-18 ? 3.9E-20 1.2E-18 ? 9.2E-19 1.50E-18 ? 1.21E-19 90% 4.4348 15.51 ? 0.15 9.75 5.46E-15 ? 8.82E-18 1.18E-15 ? 4.01E-18 2.4E-18 ? 4.8E-20 1.7E-19 ? 7.7E-19 6.50E-19 ? 1.18E-19 96% 4.4460 15.55 ? 0.12 10.00 1.81E-15 ? 3.21E-18 3.90E-16 ? 5.11E-19 1.1E-18 ? 4.7E-20 -4.7E-19 ? 8.0E-19 2.27E-19 ? 1.16E-19 96% 4.4613 15.60 ? 0.31 10.25 1.02E-15 ? 4.13E-18 2.20E-16 ? 1.12E-18 3.4E-19 ? 2.0E-20 5.3E-19 ? 9.2E-19 2.61E-19 ? 1.12E-19 92% 4.3056 15.06 ? 0.54 10.50 2.19E-15 ? 4.50E-18 4.72E-16 ? 2.47E-18 1.0E-18 ? 4.0E-20 -1.9E-18 ? 8.5E-19 5.38E-19 ? 1.31E-19 93% 4.3026 15.05 ? 0.30 11.00 2.18E-15 ? 8.85E-18 4.70E-16 ? 1.17E-18 1.1E-18 ? 5.4E-20 5.8E-19 ? 7.9E-19 4.63E-19 ? 1.31E-19 94% 4.3352 15.16 ? 0.30 11.50 2.65E-16 ? 2.88E-18 5.62E-17 ? 4.77E-19 -5.5E-19 ? -8.5E-18 -6.6E-19 ? 9.6E-19 2.61E-19 ? 1.30E-19 71% 3.3395 11.69 ? 2.40 12.50 6.14E-16 ? 3.21E-18 1.33E-16 ? 8.94E-19 1.8E-19 ? 2.0E-20 -1.2E-18 ? 6.8E-19 2.03E-19 ? 1.26E-19 90% 4.1716 14.59 ? 0.99 13.50 2.77E-16 ? 2.95E-18 6.06E-17 ? 9.70E-19 1.4E-20 ? 5.0E-21 -1.2E-18 ? 7.7E-19 2.14E-19 ? 1.26E-19 77% 3.5147 12.30 ? 2.18 129 Irradiation filename: au8.2c.adl.44. %P 40Ar(*?atm) 39Ar(K) 38Ar(Cl?atm) 37Ar(Ca) 36Ar(Atm) %Rad R Age (Ma) 6.00 2.79E-15 ? 1.76E-18 2.16E-16 ? 7.97E-19 1.6E-18 ? 9.6E-20 3.9E-19 ? 7.8E-19 6.15E-18 ? 9.33E-20 35% 4.4991 15.73 ? 0.49 6.50 7.05E-15 ? 1.46E-17 1.50E-15 ? 3.98E-18 3.9E-18 ? 6.4E-20 6.3E-19 ? 7.3E-19 1.13E-18 ? 8.43E-20 95% 4.4917 15.71 ? 0.08 7.00 8.37E-15 ? 6.00E-18 1.71E-15 ? 3.50E-18 3.7E-18 ? 6.0E-20 1.8E-18 ? 1.1E-18 2.44E-18 ? 8.66E-20 91% 4.4675 15.62 ? 0.06 7.50 6.27E-15 ? 9.66E-18 1.27E-15 ? 4.30E-18 3.7E-18 ? 7.7E-20 9.1E-19 ? 1.0E-18 1.93E-18 ? 1.74E-19 91% 4.5005 15.74 ? 0.16 8.00 1.27E-15 ? 4.93E-18 2.31E-16 ? 8.79E-19 6.4E-19 ? 2.7E-20 -1.4E-18 ? 6.8E-19 9.75E-19 ? 1.10E-19 77% 4.2193 14.76 ? 0.50 8.50 6.86E-15 ? 3.15E-18 1.31E-15 ? 2.50E-18 3.6E-18 ? 5.9E-20 5.7E-19 ? 9.2E-19 3.21E-18 ? 1.05E-19 86% 4.4960 15.72 ? 0.09 9.00 9.42E-15 ? 1.16E-17 1.79E-15 ? 2.14E-18 5.1E-18 ? 6.0E-20 2.8E-18 ? 1.1E-18 4.57E-18 ? 1.22E-19 86% 4.4907 15.70 ? 0.08 9.25 5.68E-15 ? 1.79E-17 1.17E-15 ? 3.71E-18 2.2E-18 ? 4.1E-20 1.3E-18 ? 7.6E-19 1.46E-18 ? 1.58E-19 92% 4.4963 15.72 ? 0.16 9.50 1.77E-15 ? 6.97E-18 3.73E-16 ? 1.66E-18 3.0E-19 ? 1.6E-20 5.4E-19 ? 9.0E-19 3.24E-19 ? 1.47E-19 95% 4.4913 15.70 ? 0.42 9.75 5.58E-18 ? 1.21E-18 1.21E-18 ? 3.38E-19 -4.5E-19 ? -1.6E-19 -9.8E-19 ? 1.1E-18 -1.60E-19 ? -1.80E-19 945% 43.6593 147.16 ? 153 10.00 1.80E-16 ? 1.57E-18 3.75E-17 ? 4.09E-19 -3.2E-19 ? -1.2E-18 1.4E-18 ? 8.8E-19 1.56E-19 ? 1.46E-19 74% 3.5604 12.46 ? 4.03 10.25 3.80E-16 ? 3.69E-18 8.15E-17 ? 5.73E-19 -3.5E-19 ? -1.5E-19 1.0E-18 ? 7.9E-19 1.12E-19 ? 1.46E-19 91% 4.2514 14.87 ? 1.86 10.50 4.38E-16 ? 2.37E-18 9.09E-17 ? 6.51E-19 1.5E-19 ? 2.9E-20 -1.1E-19 ? 5.4E-19 4.41E-19 ? 1.69E-19 70% 3.3767 11.82 ? 1.93 11.00 1.25E-16 ? 2.37E-18 2.52E-17 ? 2.85E-19 5.7E-20 ? 3.8E-20 -3.8E-19 ? 5.5E-19 7.44E-20 ? 1.78E-19 82% 4.0925 14.32 ? 7.30 11.50 4.48E-17 ? 1.94E-18 9.35E-18 ? 2.54E-19 -7.8E-20 ? -1.0E-18 -8.5E-19 ? 5.3E-19 4.09E-19 ? 1.65E-19 -170% -8.1284 -28.77 ? -18 12.50 1.36E-17 ? 1.37E-18 1.17E-18 ? 3.04E-19 1.6E-19 ? 1.8E-19 -1.9E-19 ? 7.7E-19 3.48E-19 ? 1.67E-19 -654% -76.4863 -290.84 ? -183 13.50 9.90E-18 ? 1.55E-18 1.93E-18 ? 3.01E-19 1.0E-20 ? 6.7E-20 -7.2E-20 ? 3.4E-19 4.72E-19 ? 1.66E-19 -1310% -67.1113 -252.57 ? -104 130 Irradiation filename: au8.2c.adl.45. %P 40Ar(*?atm) 39Ar(K) 38Ar(Cl?atm) 37Ar(Ca) 36Ar(Atm) %Rad R Age (Ma) 6.00 2.24E-15 ? 6.20E-18 1.79E-16 ? 1.27E-18 1.4E-18 ? 1.1E-19 1.8E-18 ? 6.9E-19 4.59E-18 ? 1.20E-19 40% 4.9697 17.37 ? 0.79 6.50 4.91E-15 ? 9.14E-18 1.05E-15 ? 2.80E-18 2.9E-18 ? 4.6E-20 2.1E-18 ? 9.9E-19 5.09E-19 ? 9.40E-20 97% 4.5106 15.77 ? 0.11 7.00 1.42E-15 ? 4.33E-18 3.08E-16 ? 2.98E-18 1.0E-18 ? 3.8E-20 -3.6E-19 ? 8.1E-19 5.32E-20 ? 7.79E-20 99% 4.5621 15.95 ? 0.31 7.50 1.24E-15 ? 2.96E-18 2.69E-16 ? 1.24E-18 6.8E-19 ? 4.1E-20 4.2E-20 ? 8.4E-19 1.49E-19 ? 8.71E-20 96% 4.4685 15.62 ? 0.35 8.00 2.85E-15 ? 3.02E-18 5.67E-16 ? 1.68E-18 1.9E-18 ? 8.0E-20 -1.4E-18 ? 8.1E-19 9.10E-19 ? 8.69E-20 91% 4.5561 15.93 ? 0.17 8.50 1.53E-15 ? 3.08E-18 3.27E-16 ? 1.49E-18 8.3E-19 ? 3.5E-20 -3.4E-19 ? 9.4E-19 1.62E-19 ? 9.70E-20 97% 4.5469 15.90 ? 0.32 9.00 4.21E-15 ? 8.14E-18 9.09E-16 ? 2.58E-18 2.2E-18 ? 3.1E-20 -1.3E-18 ? 7.6E-19 2.08E-19 ? 7.63E-20 99% 4.5611 15.95 ? 0.10 9.25 2.96E-15 ? 4.29E-18 6.43E-16 ? 4.60E-18 1.3E-18 ? 3.9E-20 -4.0E-19 ? 6.6E-19 2.32E-19 ? 6.42E-20 98% 4.4876 15.69 ? 0.16 9.50 3.78E-15 ? 5.93E-18 8.29E-16 ? 1.92E-18 1.2E-18 ? 4.3E-20 -4.7E-19 ? 7.8E-19 1.59E-19 ? 7.37E-20 99% 4.4967 15.72 ? 0.10 9.75 2.07E-15 ? 4.57E-18 4.49E-16 ? 1.94E-18 8.3E-19 ? 3.8E-20 -6.5E-19 ? 8.7E-19 2.28E-19 ? 7.37E-20 97% 4.4512 15.56 ? 0.19 10.00 1.42E-15 ? 4.27E-18 3.11E-16 ? 1.11E-18 3.7E-19 ? 3.1E-20 2.1E-19 ? 7.6E-19 1.76E-19 ? 6.74E-20 96% 4.4109 15.42 ? 0.24 10.25 7.68E-16 ? 3.17E-18 1.69E-16 ? 7.01E-19 -3.1E-20 ? -3.6E-21 -2.4E-19 ? 7.8E-19 1.00E-19 ? 7.13E-20 96% 4.3806 15.32 ? 0.45 10.50 2.91E-16 ? 2.53E-18 6.22E-17 ? 8.97E-19 5.6E-20 ? 1.1E-20 1.2E-19 ? 6.0E-19 -1.31E-19 ? -7.38E-20 113% 5.3033 18.53 ? 1.26 11.00 2.14E-16 ? 2.63E-18 4.61E-17 ? 5.00E-19 -1.7E-19 ? -9.1E-20 2.5E-18 ? 7.6E-19 -7.23E-21 ? -8.45E-20 101% 4.7022 16.44 ? 1.91 11.50 1.53E-16 ? 1.76E-18 3.29E-17 ? 5.08E-19 2.0E-20 ? 8.8E-21 -1.5E-19 ? 4.6E-19 -6.46E-20 ? -7.34E-20 112% 5.2295 18.27 ? 2.32 131 APPENDIX 3 Monitor and Air Data Monitor Data Sample %P 40Ar(*+atm) 39Ar(K) 38Ar(Cl+atm) 37Ar(Ca) 36Ar(Atm) %Rad R J-Value au5.1e.san.a 27 6.94E-14 ? 5.91E-17 1.23E-14 ? 1.22E-17 3.6E-17 ? 2.5E-19 1.9E-18 ? 4.1E-19 1.14E-20 ? 1.33E-19 1.000 5.6258 0.002782 ? 3.97E-06 b 27 4.03E-14 ? 2.18E-17 7.03E-15 ? 1.22E-17 1.8E-17 ? 1.2E-19 1.8E-18 ? 3.6E-19 3.61E-18 ? 1.10E-19 0.974 5.5850 0.002803 ? 5.73E-06 c 27 5.21E-14 ? 4.01E-17 9.26E-15 ? 1.14E-17 8.4E-17 ? 1.0E-18 1.9E-18 ? 3.4E-19 9.00E-19 ? 8.08E-20 0.995 5.5994 0.002795 ? 4.27E-06 d 27 5.94E-14 ? 1.39E-16 1.06E-14 ? 2.69E-17 2.7E-17 ? 1.3E-19 1.5E-18 ? 3.6E-19 9.58E-19 ? 8.70E-20 0.995 5.6010 0.002795 ? 9.79E-06 e 27 8.36E-14 ? 1.82E-16 1.49E-14 ? 2.97E-17 3.6E-17 ? 2.4E-19 1.2E-18 ? 3.0E-19 1.03E-18 ? 8.95E-20 0.996 5.6098 0.002790 ? 8.33E-06 au8.3k.san.21 21 3.09E-14 ? 2.96E-17 3.82E-15 ? 4.40E-18 9.4E-18 ? 1.2E-19 2.6E-17 ? 1.5E-18 4.74E-19 ? 1.09E-19 0.995 8.0516 0.001944 ? 3.57E-06 22 22 1.89E-14 ? 3.10E-17 2.33E-15 ? 2.35E-18 6.1E-18 ? 9.1E-20 1.1E-17 ? 8.6E-19 5.12E-19 ? 1.34E-19 0.992 8.0194 0.001952 ? 5.60E-06 23 23 1.15E-13 ? 1.32E-16 1.43E-14 ? 2.26E-17 7.2E-17 ? 4.6E-19 8.9E-17 ? 2.5E-18 1.76E-18 ? 1.20E-19 0.995 8.0043 0.001956 ? 3.88E-06 24 24 4.90E-14 ? 5.32E-17 6.04E-15 ? 1.85E-17 1.6E-17 ? 1.1E-19 3.6E-17 ? 1.4E-18 5.69E-19 ? 1.13E-19 0.997 8.0815 0.001937 ? 6.46E-06 25 25 6.01E-14 ? 6.31E-17 7.43E-15 ? 9.49E-18 1.9E-17 ? 1.8E-19 4.8E-17 ? 1.3E-18 8.33E-19 ? 1.11E-19 0.996 8.0487 0.001945 ? 3.40E-06 au8.1g.san.a 27 1.18E-13 ? 9.46E-17 1.48E-14 ? 2.49E-17 4.3E-17 ? 1.9E-19 1.1E-16 ? 7.8E-19 2.17E-18 ? 1.15E-19 0.995 7.9670 0.001965 ? 3.73E-06 b 27 3.47E-14 ? 6.55E-17 4.35E-15 ? 1.36E-17 1.1E-17 ? 1.2E-19 3.0E-17 ? 6.8E-19 1.96E-19 ? 7.08E-20 0.998 7.9769 0.001962 ? 7.26E-06 c 27 1.46E-13 ? 2.99E-17 1.82E-14 ? 1.99E-17 5.0E-17 ? 5.0E-19 1.4E-16 ? 1.5E-18 4.67E-18 ? 1.25E-19 0.991 7.9351 0.001973 ? 2.27E-06 d 27 8.82E-14 ? 1.16E-16 1.10E-14 ? 1.75E-17 2.5E-17 ? 1.8E-19 9.1E-17 ? 1.1E-18 4.66E-19 ? 7.10E-20 0.998 8.0062 0.001955 ? 4.07E-06 e 27 4.80E-14 ? 9.11E-17 5.79E-15 ? 1.16E-17 1.5E-17 ? 1.3E-19 7.1E-17 ? 7.9E-19 5.84E-18 ? 1.13E-19 0.964 8.0023 0.001956 ? 5.78E-06 au8.2j.san.a 27 6.65E-14 ? 5.26E-17 8.19E-15 ? 1.14E-17 2.1E-17 ? 1.9E-19 5.5E-17 ? 8.2E-19 2.39E-18 ? 9.27E-20 0.989 8.0229 0.001951 ? 3.26E-06 b 27 9.97E-14 ? 5.78E-17 1.13E-14 ? 5.53E-18 3.4E-17 ? 1.5E-19 7.4E-17 ? 8.6E-19 2.82E-17 ? 2.50E-19 0.917 8.0492 0.001945 ? 2.25E-06 c 27 5.05E-14 ? 1.78E-17 6.26E-15 ? 4.85E-18 1.5E-17 ? 7.8E-20 4.1E-17 ? 6.0E-19 5.02E-19 ? 9.27E-20 0.997 8.0359 0.001948 ? 1.97E-06 d 27 7.01E-14 ? 4.17E-17 8.49E-15 ? 1.59E-17 2.3E-17 ? 7.0E-20 5.5E-17 ? 1.0E-18 5.82E-18 ? 1.17E-19 0.975 8.0555 0.001943 ? 4.04E-06 e 27 6.13E-14 ? 2.91E-17 7.58E-15 ? 1.26E-17 1.8E-17 ? 1.4E-19 4.8E-17 ? 6.4E-19 2.25E-18 ? 1.13E-19 0.989 7.9960 0.001958 ? 3.58E-06 au8.3k.san.a 27 1.05E-13 ? 5.05E-16 1.34E-14 ? 2.20E-17 3.4E-17 ? 1.4E-19 8.4E-17 ? 8.3E-19 7.06E-20 ? 7.72E-20 1.000 7.8654 0.001933 ? 3.25E-06 b 27 4.18E-14 ? 2.82E-17 5.15E-15 ? 8.55E-18 1.3E-17 ? 8.2E-20 3.5E-17 ? 5.8E-19 2.15E-19 ? 9.03E-20 0.998 8.1084 0.001930 ? 3.68E-06 c 27 1.06E-13 ? 6.49E-17 1.31E-14 ? 2.09E-17 3.5E-17 ? 1.8E-19 8.2E-17 ? 1.1E-18 5.16E-19 ? 9.24E-20 0.999 8.0809 0.001937 ? 3.36E-06 d 27 6.06E-14 ? 3.80E-17 7.46E-15 ? 1.05E-17 1.8E-17 ? 1.8E-19 5.3E-17 ? 8.7E-19 6.20E-20 ? 7.33E-20 1.000 8.1241 0.001927 ? 3.05E-06 e 27 4.33E-14 ? 2.30E-17 5.35E-15 ? 6.78E-18 1.3E-17 ? 8.5E-20 3.1E-17 ? 5.1E-19 1.03E-19 ? 8.72E-20 0.999 8.0821 0.001937 ? 2.90E-06 au8.4a.san.a 27 3.64E-14 ? 2.35E-17 4.37E-15 ? 5.54E-18 1.2E-17 ? 5.2E-20 9.9E-17 ? 1.3E-18 3.25E-18 ? 1.17E-19 0.974 8.1142 0.001929 ? 3.39E-06 b 27 4.13E-14 ? 3.59E-17 5.11E-15 ? 1.19E-17 1.3E-17 ? 1.1E-19 3.4E-17 ? 7.5E-19 4.07E-19 ? 9.22E-20 0.997 8.0652 0.001941 ? 5.01E-06 132 Monitor Data (cont.) Sample %P 40Ar(*+atm) 39Ar(K) 38Ar(Cl+atm) 37Ar(Ca) 36Ar(Atm) %Rad R J-Value c 27 1.23E-13 ? 5.34E-17 1.52E-14 ? 1.43E-17 3.9E-17 ? 2.2E-19 1.0E-16 ? 1.1E-18 8.60E-19 ? 1.06E-19 0.998 8.0789 0.001937 ? 2.07E-06 d 27 1.38E-13 ? 5.38E-17 1.71E-14 ? 1.52E-17 4.3E-17 ? 2.1E-19 1.1E-16 ? 1.8E-18 1.10E-18 ? 1.16E-19 0.998 8.0691 0.001940 ? 1.95E-06 e 27 1.04E-13 ? 4.89E-17 1.24E-14 ? 1.01E-17 3.7E-17 ? 2.1E-19 2.4E-16 ? 1.5E-18 2.18E-18 ? 1.32E-19 0.994 8.3307 0.001879 ? 1.91E-06 au8.5i.san.a 27 3.31E-14 ? 2.11E-16 4.17E-15 ? 2.93E-17 9.7E-18 ? 8.0E-20 3.2E-17 ? 4.6E-19 4.30E-19 ? 1.06E-19 0.996 7.9014 0.001981 ? 1.90E-05 b 27 9.01E-14 ? 7.81E-17 1.13E-14 ? 2.04E-17 2.9E-17 ? 1.1E-19 7.2E-17 ? 1.4E-18 8.37E-19 ? 1.12E-19 0.997 7.9461 0.001970 ? 4.01E-06 c 27 3.70E-14 ? 3.03E-17 4.66E-15 ? 7.99E-18 1.1E-17 ? 1.0E-19 2.8E-17 ? 6.6E-19 7.22E-19 ? 1.10E-19 0.994 7.8992 0.001982 ? 4.18E-06 d 27 2.78E-14 ? 2.44E-17 3.49E-15 ? 1.00E-17 8.4E-18 ? 1.1E-19 2.5E-17 ? 7.4E-19 5.03E-19 ? 1.08E-19 0.995 7.9197 0.001976 ? 6.40E-06 e 27 4.14E-14 ? 3.95E-17 5.17E-15 ? 7.32E-18 1.5E-17 ? 1.9E-19 3.6E-17 ? 7.4E-19 5.67E-19 ? 1.07E-19 0.996 7.9804 0.001961 ? 3.68E-06 133 Air Standard Data Date 40Ar(*+atm) 39Ar(K) 38Ar(Cl+atm) 37Ar(Ca) 36Ar(Atm) (40/36)m (40/38)m M. Fract 1/26/07 a 1.15E-13 ? 4.92E-17 -5.79E-18 ? 4.86E-19 7.29E-17 ? 4.94E-19 5.00E-19 ? 1.37E-19 3.85E-16 ? 1.94E-18 298.7 1577 1.0027 b 1.12E-13 ? 7.40E-17 -4.56E-18 ? 7.28E-19 7.37E-17 ? 9.71E-19 -1.17E-19 ? 2.02E-19 3.76E-16 ? 1.59E-18 297.8 1519 1.0019 c 8.58E-14 ? 3.71E-17 -3.07E-18 ? 7.53E-19 5.42E-17 ? 5.75E-19 -1.64E-19 ? 1.84E-19 2.85E-16 ? 1.32E-18 300.7 1583 1.0044 1/27/07 b 1.11E-13 ? 5.77E-17 -7.68E-18 ? 5.35E-19 7.08E-17 ? 6.73E-19 4.91E-20 ? 2.03E-19 3.77E-16 ? 1.76E-18 295.7 1573 1.0002 1/28/07 a 1.16E-13 ? 1.00E-16 -3.90E-19 ? 3.10E-19 7.40E-17 ? 6.67E-19 8.32E-19 ? 1.81E-19 3.83E-16 ? 1.50E-18 301.7 1561.5 1.0052 b 1.15E-13 ? 1.41E-16 -5.93E-20 ? 2.57E-19 7.33E-17 ? 5.21E-19 9.75E-19 ? 1.63E-19 3.84E-16 ? 1.73E-18 299.1 1564.7 1.0 1/29/07 a 1.17E-13 ? 1.93E-16 -7.26E-18 ? 4.42E-19 7.39E-17 ? 7.39E-19 5.34E-19 ? 2.82E-19 3.91E-16 ? 9.14E-19 300.2 1590.1 1.0 b 1.14E-13 ? 7.18E-17 -6.75E-18 ? 4.47E-19 7.20E-17 ? 5.67E-19 2.04E-19 ? 1.35E-19 3.80E-16 ? 8.96E-19 299.6 1579.9 1.0 1/30/07 a 1.15E-13 ? 8.00E-17 -6.15E-18 ? 4.25E-19 7.30E-17 ? 7.83E-19 3.17E-19 ? 1.62E-19 3.85E-16 ? 6.52E-19 299.0 1577.0 1.0 b 1.14E-13 ? 1.70E-16 -7.03E-18 ? 4.07E-19 7.23E-17 ? 5.32E-19 2.22E-19 ? 1.82E-19 3.81E-16 ? 6.63E-19 299.0 1576.4 1.0 c 1.08E-13 ? 3.69E-17 -6.53E-18 ? 3.94E-19 6.95E-17 ? 5.41E-19 -1.19E-20 ? 1.91E-19 3.63E-16 ? 6.05E-19 298.9 1561.6 1.0 1/31/07 a 1.19E-13 ? 1.17E-16 -6.46E-18 ? 4.38E-19 7.80E-17 ? 1.34E-18 4.86E-20 ? 2.11E-19 4.00E-16 ? 1.98E-18 298.5 1531.6 1.0 b 1.16E-13 ? 3.39E-17 -6.37E-18 ? 4.98E-19 7.35E-17 ? 5.82E-19 4.41E-20 ? 1.26E-19 3.88E-16 ? 7.57E-19 297.8 1572.4 1.0 2/2/07 a 1.13E-13 ? 5.44E-17 -6.45E-18 ? 4.66E-19 7.22E-17 ? 4.95E-19 7.23E-20 ? 1.56E-19 3.77E-16 ? 7.86E-19 300.1 1568.4 1.0 2/4/07 a 1.17E-13 ? 4.41E-17 -6.22E-18 ? 3.06E-19 7.34E-17 ? 5.88E-19 1.86E-19 ? 2.04E-19 3.89E-16 ? 8.17E-19 299.3 1586.2 1.0 3/3/07 a 1.17E-13 ? 1.37E-16 -4.04E-18 ? 5.60E-19 7.50E-17 ? 6.70E-19 9.16E-20 ? 1.82E-19 4.02E-16 ? 1.60E-18 290.5 1558 0.9958 b 1.18E-13 ? 1.15E-16 -7.11E-18 ? 4.24E-19 7.68E-17 ? 7.26E-19 6.57E-19 ? 2.20E-19 4.06E-16 ? 1.10E-18 291.7 1542 0.9968 c 1.17E-13 ? 2.22E-16 -5.93E-18 ? 8.00E-19 7.76E-17 ? 1.40E-18 -9.92E-20 ? 3.17E-19 4.02E-16 ? 1.78E-18 291.0 1509 0.9962 3/4/07 a 1.15E-13 ? 3.66E-16 -7.33E-18 ? 4.62E-19 7.47E-17 ? 6.25E-19 4.27E-19 ? 2.45E-19 3.95E-16 ? 2.27E-18 291.2 1540 0.9963 b 1.15E-13 ? 2.00E-17 -7.05E-18 ? 5.56E-19 7.51E-17 ? 1.04E-18 2.10E-19 ? 2.03E-19 3.97E-16 ? 7.37E-19 289.0 1528.0 0.9945 3/5/07 a 1.18E-13 ? 4.46E-17 -6.90E-18 ? 4.95E-19 7.59E-17 ? 6.03E-19 -1.48E-21 ? 1.79E-19 4.07E-16 ? 9.19E-19 290.2 1556.1 0.9956 b 1.20E-13 ? 6.23E-17 -7.77E-18 ? 2.89E-19 7.56E-17 ? 9.63E-19 -6.21E-20 ? 1.25E-19 4.15E-16 ? 9.72E-19 289.3 1589.6 0.9948 3/6/07 a 1.16E-13 ? 8.35E-17 -6.44E-18 ? 5.50E-19 7.49E-17 ? 9.55E-19 -2.27E-21 ? 1.74E-19 4.03E-16 ? 1.69E-18 287.9 1548.6 0.9936 b 1.16E-13 ? 8.35E-17 -1.50E-17 ? 3.85E-19 7.33E-17 ? 9.54E-19 -1.26E-18 ? 1.76E-19 4.02E-16 ? 1.69E-18 288.5 1581.2 0.9941 3/7/07 a 6.95E-14 ? 6.85E-17 -3.88E-18 ? 4.69E-19 4.43E-17 ? 3.51E-19 -4.36E-19 ? 1.62E-19 2.40E-16 ? 1.09E-18 289.1 1566.7 0.9946 3/8/07 a 1.15E-13 ? 6.88E-17 3.02E-18 ? 7.28E-19 7.58E-17 ? 3.26E-19 1.23E-18 ? 1.49E-19 3.93E-16 ? 9.16E-19 292.0 1513.1 0.9971 b 6.65E-14 ? 2.46E-17 -2.05E-18 ? 5.55E-19 4.28E-17 ? 4.17E-19 8.59E-21 ? 1.24E-19 2.28E-16 ? 6.15E-19 291.8 1554.7 0.9968 3/9/07 a 6.81E-14 ? 7.06E-17 -3.98E-18 ? 2.21E-19 4.36E-17 ? 2.80E-19 3.09E-19 ? 1.48E-19 2.33E-16 ? 4.67E-19 292.0 1560.5 0.9971