TECTONIC EVOLUTION OF A CALEDONIAN-AGED CONTINENTAL BASEMENT ECLOGITE TERRANE IN LIVERPOOL LAND, EAST GREENLAND 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 committee. This thesis does not include proprietary or classified information. ______________________________________ John Wesley Buchanan II Certificate of Approval: ____________________________ ________________________ Willis E. Hames Mark G. Steltenpohl, Chair Professor Professor Geology Geology ____________________________ ________________________ Ashraf Uddin Joe F. Pittman Associate Professor Interim Dean Geology Graduate School TECTONIC EVOLUTION OF A CALEDONIAN-AGED CONTINENTAL BASEMENT ECLOGITE TERRANE IN LIVERPOOL LAND, EAST GREENLAND John Wesley Buchanan II A Thesis Submitted to the Graduate Faculty of Auburn University in Partial Fulfillment of the Requirements for the Degree of Master of Science Auburn, Alabama May 10, 2008 iii TECTONIC EVOLUTION OF A CALEDONIAN-AGED CONTINENTAL BASEMENT ECLOGITE TERRANE IN LIVERPOOL LAND, EAST GREENLAND John Wesley Buchanan II Permission is granted to Auburn University to make copies of this thesis at its discretion, upon request of individuals or institutions and at their expense. The author reserves all publication rights. ______________________________ Signature of Author ______________________________ Date of Graduation iv VITA John Wesley Buchanan II, son of Jerry Wesley and Patricia Ann Buchanan was born on November 29, 1983 in Franklin, Tennessee. During Wesley?s middle and high school years, he was involved in the Boy Scouts of America and earned the rank of Eagle Scout. During his scouting years, he hiked in the southern Rocky Mountains, the Appalachians, and the Canadian interior, learning to navigate backcountry lands by map and compass a skill that would later become very valuable. He graduated with honors from Battle Ground Academy in Franklin, Tennessee in 2002. Upon graduation, Wesley enrolled at the University of Kentucky, where by a rather circuitous route found and fell in love with geology. While at the University of Kentucky, Wesley enjoyed geology based field trips in the states of Kentucky, Tennessee, North Carolina, South Carolina, Georgia, Alabama, Mississippi, Louisiana, Missouri, Kansas, Colorado, Utah, Arizona, and New Mexico. After completing almost all of his course work, he entered the graduate program at Auburn University in the fall of 2006. By the wonders of a correspondence course he graduated in August 2007 with a Bachelor of Science in Geology. While attending Auburn University, Wesley performed field work in East Greenland, North Norway, and the Southern Appalachians. In the spring of 2008, Wesley graduated from Auburn University with a Masters of Science in Geology. v THESIS ABSTRACT TECTONIC EVOLUTION OF A CALEDONIAN-AGED CONTINENTAL BASEMENT ECLOGITE TERRANE IN LIVERPOOL LAND, EAST GREENLAND John Wesley Buchanan II Master of Science, May 10, 2008 (M.S., Auburn University, 2008) (B.S., University of Kentucky, 2007) 122 Typed Pages Directed by Mark G. Steltenpohl Liverpool Land is located in an interior position within the East Greenland Caledonides. Due to the remoteness of the field locality, very little work has been published on the rocks and structures of Liverpool Land. The main focus of this thesis work, therefore, has been to aid in establishing a metamorphic and deformational framework for rocks in the area. Southern Liverpool Land is divided by the Gubbedalen Shear Zone, a greenschist-facies, ~500 m thick, N-dipping high-strain zone with a polyphase history, including tops-south (contraction) as well as tops-north (extension) displacement (discovered and documented in this study). The hanging wall to the north vi is characterized by the Krummedal Sequence, which is intruded by the Caledonian, Silurian Hurry Inlet Granite and Hodal-Storefjord Monzodiorite plutons. The Krummedal Sequence and Monzodiorite unit are intruded by several north-south striking lamprophyre dikes that are herein dated to 262 and 264 Ma by 40Ar/39Ar methods performed on crystals of phlogopite. The footwall block of the Gubbedalen Shear Zone is characterized by a migmatitic orthogneiss basement complex, with felsic and mafic phases. Included within the felsic orthogneiss are eclogites, garnet-pyroxenites, amphibolites, and ultramafic bodies. These mafic bodies occur as boudins and pods wrapped by crystal-plastic mylonites that overprint the gneissosity in the country rocks. Peak temperature and pressure conditions of eclogitization are herein constrained by geothermobarometry on minerals forming the eclogite-facies assemblage (i.e., garnet and omphacite), and are ~867?C and a minimum pressure of 18.2 kbars. Cutting across all lithologies in the footwall is a stockwork of granitic veins and dikes. Similarities between the orthogneiss complex of the footwall block and parts of the Western Gneiss Region in Norway imply that the footwall block may in fact be an orphaned crustal slice from the Baltic craton. This interpretation explains how the eclogites of southern Liverpool Land occur within the supposed upper plate of the Caledonian collisional event. vii ACKNOWLEDGEMENTS The author thanks the Geological Society of America for the financial support of this work. Many thanks are also extended to Dr. Muriel Erambert, University of Oslo, for her knowledge and guidance while performing microprobe analysis; Dr. David Moecher, University of Kentucky, for his knowledge of high pressure rocks and microprobe analysis and for conducting detailed mineral element mapping; Dr. Willis Hames, Auburn University, for use of his lab, ANIMAL, and for many discussions on mineral chemistry; Lars Eivind Augland and Dannena Bowman, for helping to unravel the complicated history of Liverpool Land; Per Inge Myhre, for helping us set up and run base camp in East Greenland; and Dr. Arild Andresen, University of Oslo, for being himself and everything that entails. viii Style manual used: United States Geological Survey Suggestions to Authors ? 6th Edition Computer software used: Microsoft Word 2003, Microsoft Excel 2003, Microsoft Powerpoint 2003, Adobe Photoshop, Isoplot, Corel Designer 12 ix TABLE OF CONTENTS LIST OF FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvi I. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 General Geology of East Greenland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Introduction to the Problem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Thesis Objectives and Methods of Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . 7 II. GEOLOGY OF SOUTHERN LIVERPOOL LAND . . . . . . . . . . . . . . . . . . . . . . . . . . 9 General Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Northern Hanging Wall Block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Southern Footwall Block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13 Gubbedalen Shear Zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 III. PETROLOGY AND PETROGRAPHY OF ECLOGITES . . . . . . . . . . . . . . . . . . . . 34 Petrography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Mineral Chemistry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 Geothermobarometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Thermometry Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Barometry Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 IV. 40Ar/39Ar GEOCHRONOLOGY OF LAMPROPHYRE DIKES . . . . . . . . . . . . . . . 46 Petrography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 40Ar/39Ar Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 40Ar/39Ar Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 V. DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 Alternate Explanation of Liverpool Land Eclogites . . . . . . . . . . . . . . . . . . . . . . 58 VI. CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 REFERENCES CITED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 APPENDIX A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 x APPENDIX B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 APPENDIX C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 xi LIST OF FIGURES Figure 1. Map showing the extent of the Caledonian-Appalachian mountain belt (blue areas). The yellow-orange areas represent basement shield rocks (Stampfli, 2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Figure 2. Cartoon representing the subduction of Baltica beneath the Laurentian margin (modified from H. Fossen, personal communication to Steltenpohl, 2005) . . . . . 2 Figure 3. Geologic map of the East Greenland Caledonides, showing the major rock units and fault structure (Modified after Mandler and Jokat, 1998). Black rectangle outlines the area of the Liverpool Land geologic map shown in Figure 4. Cross section along red line is illustrated in color beneath the geologic map (Henricksen et al., 2000) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Figure 4. Geologic map of the central portion of Liverpool Land East Greenland with northern and southern field areas outlined with black boxes (Modified from Friderichsen and Surlyk, 1976) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Figure 5. Images of rocks from the hanging wall of the Gubbedalen Shear Zone. A. Krummedal Sequence showing weak gneissic foliation with a metasedimentary biotite schist inclusion. B. Boulder of Hurry Inlet Granite showing lighter felsic injections into a mafic-rich phase with inclusion of coarse grained granite in the top of boulder. C. Photomicrograph in cross polars of Hodal-Storefjord Monzodiorite showing little internal deformation. D. Lamprophyre dike located within the northern field area. Notice the inclusions of country wall rock within the dike. E. Phlogopite and plagioclase phenocrysts contained within the lamprophyre dike. F. Dolerite dike intruding the Hodal-Storefjord Monzodiorite with contact metamorphic areoles. Notice fining (darkening) of igneous fabric in the dolerite as the contact (in red) is approached . . . . . . . . . . . . . . . . . . . . . . . . . 12 Figure 6. General geologic map of the southern field area depicting the location of the Gubbedalen Shear Zone. Refer to Figure 4 for location of the field area within Liverpool Land. Contour lines are represented as dashed lines (contour interval = 100 meters). Blue lines represent rivers and streams. Blue closed polygons represent lakes. A to A? indicates the location of the cross section produced in Figure 16B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Figure 7. Rocks within the footwall of the Gubbedalen Shear Zone. A. Mafic orthogneiss near the bottom of the shear zone. Note the sheared felsic stringers of xii quartz and feldspar, sigma clasts indicating tops right in the photo, S2 mylonitic foliation parallels pencil. B. Photomicrograph in plane light of mafic orthogneiss showing S0 gneissic foliation composed of alternating biotite layers with quartz- feldspar layers. C. Felsic orthogneiss preserving S0 gneissic foliation (looking perpendicular to foliation). D. Photomicrograph in plane light of felsic orthogneiss showing S0 gneissic foliation composed of less mafic alternating biotite and hornblende layers with quartz-feldspar layers. E. Highly folded and sheared felsic migmatite. F. Blebby migmatite gneiss with stretched cigar shaped neosomes (looking to the north, parallel to lineation). Note the migmatite foliation S1 sheared into a tops-left mylonitic shear zone in the top of the image. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Figure 8. Geologic map illustrating S0/S1 foliation planes measured in the southern field area. Inset is a lower hemisphere stereographic projection of poles to S0/S1; n = 22 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Figure 9. Geologic map illustrating L0/L1 lineations measured in the southern field area. Inset is a lower hemisphere stereographic projection of L0/L1 lineations; n = 11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Figure 10. Field images of eclogites and related mylonites within the footwall of the Gubbedalen Shear Zone. A. Boudinaged eclogite pod within the felsic orthogneiss. Note the mylonitization (S2) of the migmatite around the boudin and the presence of felsic veins interpreted to be decompressional melts. B. Eclogite CP-52A with garnet-rich layers (S2, eclogite-facies compositional layering) and felsic decompressional melt veins with large amphibole crystals . . . . . . . . . . . . 20 Figure 11. A. View of a sigmoidal shaped crystal-plastic mylonite wrapping over the top of a small mafic boudin (backpack for scale). B. Line drawing of a mylonite sheathed boudin in A. Solid lines represent mineral elongation lineation and dashed lines represent the vertical joint faces. C. Mylonite (looking perpendicular to foliation and parallel to lineation) from vertical face of a boudin sheathing a mafic lens with large (2.5 cm) potassium feldspar sigma clasts entrained and rotated with tops-right movement. D. Stereogram of data for outcrop shown in A, B, and C, with S2 mylonitic foliation in blue and L2 mineral elongation lineation in black. E. Photomicrograph in cross polarized light of a mylonite wrapping an eclogite boudin. S-C fabric is preserved indicating dextral movement. The shear fabric has been mostly recrystallized and annealed. F. Photomicrograph of myrmekite grains found throughout the boudin wrapping mylonites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Figure 12. Geologic map illustrating S2 and S3/S4 foliation planes measured in the southern field area. Inset is a lower hemisphere stereographic projection of poles to foliation planes. A. S3/S4 foliations within the Gubbedalen Shear Zone; n = 24. Dashed red line is an average S0/S1 foliation plane. Small circle fit through data xiii (red partial circle) indicates a cone axis at N32?W, 25?W. B. S2 foliations of mylonite shear zones associated with eclogite boudins and ?rogue? shears; n = 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Figure 13. Geologic map illustrating L2 and L3/L4 lineations. Inset is a lower hemisphere stereographic projection of elongation lineations. A. L3/L4 lineations within the Gubbedalen Shear Zone; n = 34. Dashed red line is an average S0/S1 foliation plane. B. L2 lineations of shear zones associated with eclogite boudins and ?rogue? shears; n = 25. Small circle fit through data (red circle) indicates a cone axis at N27?W, 19?NW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Figure 14. Images and photomicrographs of the contractional lower part of the Gubbedalen Shear Zone. All photos perpendicular to foliation and parallel to lineation. A. Mylonitized migmatitic gneiss and syntectonic granite found within the lower part of the shear zone . B. Mafic-rich ultramylonites with feldspar sigma clasts indicating tops-right (south) thrust movement. C. Ultramylonite (S3) cutting across a mylonitized migmatite (S2), documenting tops-right (south) thrust movement. D. Photomicrograph in cross polarized light from granitic mylonite in image A. Micafish and sigma clasts indicate dextral (tops-up and south) reverse slip movement. Note quartz has subgrains and the shear fabric is dynamically recrystallized. E. Photomicrograph in cross polars from same thin section as D showing a dextral quartz and feldspar aggregate sigma clast . . . . . 27 Figure 15. Studies from the extensional overprint in the upper parts of the Gubbedalen Shear Zone. A. Ultramylonitic extensional shear zone (S4) cutting across and retrograding the prior contractional mylonitic fabric (S3). B. S4 extensional shear zone cutting a granitic injection. C. Reverse-slip crenulations documenting tops- down-to-the left (north) extension. D. Carbonate breccia zone at the northern margin of the shear zone in contact with the Hurry Inlet Granite. E. Photomicrograph in plane light of extensional overprint upon the S3 mylonitic fabric. Note the microfolds within the quartz ribbons, and C? shear bands. F. Photomicrograph in cross polarized light of dextral mica fish. Polycrystalline quartz ribbons contain sugbrains and recrystallized grain shape preferred orientation documenting sinistral extensional shear . . . . . . . . . . . . . . . . . . . . . . 29 Figure 16. A. Photo mosaic of the Gubbedalen Shear Zone (outlined in red) looking to the east along a valley wall. Extensional and contractional zones are separated by the blue line. B. Schematic cross section from A to A? of the Gubbedalen Shear Zone and surrounding terranes (location of cross section marked in Figure 6). Shear couples within the shear zone represent the direction of shear. Straight lines represent the mylonitic foliation and wavy lines represent the migmatitic foliation. C. Felsic dikes within the bottom of the shear zone (looking north) pulled into parallelism with the shear zone?s foliation. D. Unaffected felsic dikes from a canyon wall (looking east) well south of the shear zone . . . . . . . . . . . . . 31 xiv Figure 17. A. Stereographic projection of poles to planes from all foliation data (S0, S1, S2, S3, and S4) collected in the southern field area. B. Stereographic projection of all lineations (L0, L1, L2, L3, and L4) collected in the southern field area (n equals the number of measurements) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Figure 18. Simplified geologic map showing the location of eclogite samples that were petrographically and chemically analyzed (CP-47: 70? 34.937?N, 22? 13.770?W; CP-52A: 70? 34.633?N, 22? 15.220?W; and CP-92: 70? 35.362?N, 22? 12.106?W) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Figure 19. A. Eclogite CP-52A in plane light, notice the thin rim of retrograde hornblende growing on the omphacite grain. B. Eclogite CP-92 in plane light with fine-grained lamellar plagioclase-clinopyroxene-hornblende symplectites. C. Zoomed in Back Scatter Electron image of the area depicted in B. D. Eclogite CP-47 in plane light showing coarse grained wormy plagioclase-clinopyroxene- hornblende symplectites. E. Back Scatter Electron image of sample CP-47 (field of view is ~1 cm). F. Quartz exsolution rods within remnant omphacite grain and small low-sodium clinopyroxene nucleating in plagioclase within sample CP-47 in plane light. Abbreviations used in figure. Grt = Garnet, Cpx = low-Na clinopyroxene, Qtz = quartz, Plag = Plagioclase, Zr = Zircon, Omp = Omphacite, Hbl = Hornblende . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Figure 20. End member compositions of analyzed garnet grains from eclogite samples displayed on a ternary diagram (after Coleman et al., 1965) . . . . . . . . . . . . . . . .39 Figure 21. End member compositions of analyzed clinopyroxene grains from eclogite samples displayed on a ternary diagram (after Morimoto et al., 1988) . . . . . . . . 41 Figure 22. Element maps of calcium (left) and sodium (right) of eclogite CP-52A, with lighter colors being more enriched in the element. The central grain is an omphacite with a garnet grain to the top left of each image. Notice the fine grained symplectite that is forming along some fractures within the omphacite. Image is approximately 1 cm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 Figure 23. End member compositions of analyzed amphibole grains from eclogite samples on a Silicon versus Na+K diagram (after Deer et al., 1992) . . . . . . . . . 42 Figure 24. A. Photomicrograph in plane light from sample M-14C of euhedral phologopite and plagioclase phenocrysts within a matrix of phlogopite, plagioclase, and opaques (in images Phl = phlogopite and Plag = plagioclase). B. Optically zoned plagioclase phenocryst within M-14C (cross-polarized light). Steel blue birefringence of the plagioclase is believed to be a result of the thin section being slightly too think. C. Phlogopite and plagioclase phenocrysts within M-21 (plane light). Note the radiogenic halo within the tan-brown phlogopite grain in contact with matrix feldspar (lower right) . . . . . . . . . . . . . . 47 xv Figure 25. Plateau diagram produced from the incremental heating data collected from sample M-14C. Inset. Probability density diagram created from the SCTF data from sample M-14C. Individual crystal data represented as points with error bars (error bars are1?). Prob. = the probability that the SCTF data could be part of a normal distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 Figure 26. Plateau diagram produced from the incremental heating data collected from sample M-21. Inset. Probability density diagram created from the SCTF data from sample M-21. Individual crystal data represented as points with error bars (error bars are1?). Prob. = the probability that the SCTF data could be part of a normal distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Figure 27. A. Subduction of the Baltic lithospheric slab underneath Laurentia during continental subduction. B. Failure of the crust after reaching eclogite-facies conditions, resulting in the uplift of a crustal slice (orthogneiss footwall terrane), creating a sense of normal movement along the contact with the overriding plate. X?s represent brittle faulting occurring in the overriding Laurentian crust. C. Continued uplift of the crustal slice to shallow crustal levels (modified from Chemenda et al., 1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 Figure 28. Devonian detachment faults within the East Greenland and Scandinavian Caledonides (Ebbing et al., 2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57 Figure 29. Paleogeographic plate reconstruction during the Permian (~260 Ma) showing the Liverpool Land region (red star) against Lofoten, Norway (blue star) (Blakey, 2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 Figure 30. A and B. Location of the Lofoten Islands of northern Norway (Steltenpohl et al., 2004). C. Probability density diagram with hydrothermal muscovite age from Lofoten fault zone in black (data from Steltenpohl et al., 2004) and phlogopite crystallization age from Liverpool Land lamprophyres in blue and red. D. Diagram depicting the Permian metamorphic core complex of Lofoten (Steltenpohl et al., 2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 xvi LIST OF TABLES Table 1. Metamorphic and structural history of Liverpool Land comparing hanging wall and footwall blocks to the Gubbedalen Shear Zone (1This study; 2Bowman, 2008; 3Augland, 2007; 4personal communication to Augland, 2008; 5Strachan et al., 1995; 6Kalsbeek et al., 1998) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Table 2. Table contains averaged weight percent oxides from multiple (n = number) microprobe analyses of garnet, pyroxene, plagioclase, and amphibole . . . . . . . . 38 Table 3. Summary table of geothermobarometric calculations. . . . . . . . . . . . . . . . . . . . 45 1 I. INTRODUCTION General Geology of East Greenland The Caledonian mountain belt is the northern most continuation of the Appalachian mountain belt that stretches over 10,000 kilometers and represents the suturing together of the Pangaean supercontinent (Figure 1). This study focuses on East Greenland, which comprises the western side of the Caledonian collisional mountain belt; the eastern side of the mountain belt lies in Norway, Sweden, and the United Kingdom. The East Greenland Caledonides are dominated by Precambrian and Paleozoic metamorphic rocks that average ~300 kilometers wide and extend for 1,400 kilometers between 70? - 82? N and 20? - 30? W, roughly parallel to the coast (Haller, 1971). The classic model for the formation of the Caledonian orogen evokes the Silurian collision and partial subduction of the Baltic craton beneath the Laurentian craton (Figure 2). The polarity of the collisional zone is documented by a Caledonian-aged calc-alkaline plutonic arc in East Greenland and high pressure and ultra-high pressure eclogites exposed in the Western Gneiss Region of coastal Norway (Hodges et al., 1982). The collision emplaced a westward-verging thrust complex upon the ancient Laurentian margin (Figures 2 and 3). ?Thick-skinned? west-directed thrusting in coastal areas of East Greenland grade into multiple ?thin-skinned? fold and thrust belts farther west into the foreland (Higgins and Leslie, 2000). A mirror image east-verging fold and thrust belt is seen in the Scandinavian Caledonides (Figure 2; Roberts and Gee, 1985). 2 Figure 1. Map showing the extent of the Caledonian-Appalachian mountain belt (blue areas). The yellow-orange areas represent basement shield rocks (Stampfli, 2004). Figure 2. Cartoon representing the subduction of Baltica beneath the Laurentian margin (modified from H. Fossen, personal communication to Steltenpohl, 2005). 3 Figure 3. Geologic map of the East Greenland Caledonides, showing the major rock units and fault structures (modified from Mandler and Jokat, 1998). Black rectangle outlines the area of the Liverpool Land geologic map shown in Figure 4. Cross section along red line is illustrated in color beneath the geologic map (Henricksen et al., 2000). 4 Introduction to the Problem Liverpool Land is a horst-block (Figure 3) of Archean-Caledonian crystalline basement that is intruded by Caledonian plutons (Figure 4). Eclogites have been known to exist within the crystalline basement of Liverpool Land since the 1930?s (Kranck, 1935; Sahlstein, 1935). Eclogites are high temperature and (ultra-) high pressure metamorphic rocks formed under extreme crustal conditions, and are vital indicators of plate tectonic processes. Classically, eclogite formation is predicted to occur within the subducting crustal slab. Contrary to this prediction however, Liverpool Land eclogites occur within the supposed upper plate (Laurentian) of the collisional zone, posing a problem to the model of wholesale asymmetric subduction of Baltica beneath Laurentia. The Liverpool Land eclogites were recently ?rediscovered? using more modern analytical techniques, but all that is published is an abstract by Hartz et al. (2005). Hartz et al. (2005) report a ~395 Ma date on zircons from a Liverpool Land eclogite, using U- Pb TIMS analysis. Likewise, Hartz et al. (2005) report that these eclogites were formed under ultra-high pressure (~850?C and >25kbars). The presence of Caledonian (~395 Ma) eclogites poses another geologic problem in that an adjacent Caledonian granitic pluton imprecisely dated to ~435 Ma (Hansen and Steiger, 1971; Coe and Cheney, 1972; Coe, 1975) completely escaped the eclogite-facies metamorphism. The goal of present thesis research is to unravel the tectonic evolution of southern Liverpool Land in an attempt to explain the presence of Caledonian eclogites, possibly ultra-high pressure ones, within the supposed upper plate of the collisional orogen, and to reconcile the boundary between the eclogite-bearing basement terrane and its adjacent terrane containing earlier intruded and unmetamorphosed Caledonian plutons. 5 Figure 4. Geologic map of the central portion of Liverpool Land East Greenland with northern and southern field areas outlined with black boxes (modified from Friderichsen and Surlyk, 1976). 6 In the summer of 2006, field work was focused on two areas within Liverpool Land (Figure 4). The individual objectives for the two field areas varied and more field time was allotted to the southern one. The southern field area, containing the Gubbedalen Shear Zone, was the center of attention for my thesis study and geologic mapping and structural analysis was focused there. The goals for field work in the northern area were to understand the intrusive relationships and to characterize the lamprophyre dikes present in that area. Field investigations in Liverpool Land were performed in conjunction with a research expedition from the University of Oslo, Norway. The research team consisted of three Auburn University participants, Wesley Buchanan, Dannena Bowman, and Dr. Mark Steltenpohl, and three University of Oslo workers, Lars Eivind Augland, Per Inge Myhre, and Dr. Arild Andresen. Field and laboratory studies were divided among the three Master?s candidates, in an effort to piece together the tectonic evolution of the area. As part of the expedition, I was charged to characterize the structural and kinematic relationships of the different lithologic units and combine these observations with previous work to define the deformation sequence for southern Liverpool Land. I was also charged with the petrology and petrography of the eclogites and lamprophyre dikes. Dannena Bowman was responsible for petrographically describing the country rocks of the terrane and performing 40Ar/39Ar thermochronology to constrain their cooling history (Bowman, 2008). Lars Eivind Augland was charged with conducting U-Pb isotopic studies to determine the absolute ages of igneous crystallization and eclogitization (Augland, 2007). 7 Thesis Objectives and Methods of Investigation Five objectives of the present investigation needed to resolve the tectonic evolution of Liverpool Land are as follows: (1) to map and describe the lithologies and structures within the region; (2) to characterize the structural framework of the eclogites; (3) to estimate the pressure and temperature of eclogitization; (4) to constrain the timing of the lamprophyre dikes; and (5) to synthesize the results and incorporate them with those of the 2006 expedition colleagues to develop a tectonic model for the region. Standard structural mapping techniques were used in the field to characterize the kinematic and geometric relationships of lithologic units. A Brunton compass was used to obtain attitudes of pertinent rock features (i.e., foliation planes and lineations). The structural data was analyzed using lower-hemisphere stereographic projection software to characterize meso- and macroscopic relationships. Rock samples were collected from eclogites, lamprophyres, and mylonites for laboratory analysis. Sample locations were recorded with a handheld GPS unit. Polished thin sections of eclogite samples and standard thin sections of lamprophyre samples were commercially made. Oriented samples of mylonites were collected and thin sections commercially made in order to determine the kinematics of the samples. Using petrographic microscopes at Auburn University, mineralogical, textural, kinematic, and microstructural analyses were performed to characterize the metamorphic and structural framework of the field area. Microprobe analysis was performed on eclogite samples using the facilities at the University of Oslo under the direct supervision of Dr. Muriel Erambert, an expert on Caledonian eclogites. Further microprobe analysis was performed using the facilities at 8 the University of Kentucky, with the guidance of Dr. David Moecher. The chemical compositions of garnet, pyroxene, plagioclase, and amphibole were determined using Wavelength-Dispersive System (WDS) analysis. Other previously unknown minerals were identified using Energy-Dispersive System (EDS) analysis. The wavelength- dispersive system analyses were used to quantify the temperature and pressure of eclogite formation, using elemental partitioning geothermobarometry and Excel? worksheets developed by the author. Phlogopite grains were separated from lamprophyre dikes and dated using 40Ar/39Ar techniques in the Auburn Noble Isotope Mass Analysis Laboratory (ANIMAL), under the supervision of Dr. Willis Hames. 9 II. GEOLOGY OF SOUTHERN LIVERPOOL LAND General Statement Field investigations conducted in 2006, revealed the presence of a major east-west trending, north-dipping ductile shear zone bisecting southern Liverpool Land, hereafter named the Gubbedalen Shear Zone (Figure 4; Buchanan et al., 2007). This shear zone juxtaposes two vastly distinct terranes both in terms of lithology and their structural and metamorphic development. The hanging wall (Figure 4) is characterized by a partially migmatized metasedimentary package (i.e., Krummedal Sequence) and several Caledonian plutons (i.e., Hurry Inlet Granite and Hodal-Storefjord Monzodiorite). The Caledonian plutons are in contact with the shear zone and are mostly undeformed except where the margin of the shear zone is approached. The footwall block (Figure 4) to the south is a highly deformed basement orthogneiss complex that contains the eclogites reported by Hartz et al. (2005). Rocks contained within the footwall block record peak and retrograde metamorphic events. An eclogite and granulite-facies event is recorded within the rarely preserved boudinaged eclogites. Amphibolite-facies metamorphic minerals and textures are clearly retrograde within the eclogites, and although it is less obvious in their encapsulating orthogneisses, the latter must have followed the same metamorphic path. Table 1 contains an outline of the structural and metamorphic history of Liverpool Land developed from the results of the 2006 expedition and provides the context of the structural nomenclature used. 10 Hanging Wall Block Age Footwall Block Dolerite dikes and flood basalts 65 Ma Dolerite dikes and flood basalts Sedimentation in Jameson Land Jurassic and Triassic Sedimentation in Jameson Land Intrusion of lamprophyre dikes 262, 264 Ma1 Devonian sediments deposited on top of the Hurry Inlet Granite 380-350 Ma D4 ? Extensional Gubbedalen Shear Zone dated by 40Ar/39Ar ? S4 mylonites extend and cut S3 ? Formation of L4 mineral elongation lineation 380 Ma2 D4 ? Extensional Gubbedalen Shear Zone dated by 40Ar/39Ar ? S4 mylonites extend and cut S3 ? Formation of L4 mineral elongation lineation D3 ? Contractional Gubbedalen Shear Zone dated by syntectonic granitic dikes ? S3 mylonitic foliation cuts S1 and S2 ? Formation of L3 mineral stretching lineation 386 Ma3 D3 ? Contractional Gubbedalen Shear Zone dated by syntectonic granitic dikes ? S3 mylonitic foliation cuts S1 and S2 ? Formation of L3 mineral stretching lineation Joining of the hanging wall and footwall blocks along the Gubbedalen Shear Zone 388 Ma3 Late D2 ? Amphibolite-facies retrogression - Formation of S2 shear zones around boudins, rogue shears, and L2 mineral stretching lineations 399-388 Ma Middle D2 ? Granulite-facies retrogression preserved in eclogites 399 Ma3 Early D2 ? Eclogite-facies metamorphism 400-410 Ma (Caledonian)4 D1 ? Formation of S1 migmatitic foliation and L1 constrictional neosome fold axes Intrusion of Hodal-Storefjord Monzodiorite 424 Ma3 Hurry Inlet Granite magma pulses 445, 438 Ma3 Amphibolite-facies metamorphism of Krummedal Sequence ? formation of weak gneissic foliation 950 Ma5 1660-410 Ma (Relative) D0 ? Formation of S0 gneissic foliation and L0 mineral aligning lineations within the orthogneiss ? Must postdate protolith emplacement and predate D1 Maximum age for the deposition of the Krummedal Sequence 1100 Ma6 1660 Ma3 Protolith age for eclogites Table 1. Metamorphic and structural history of Liverpool Land comparing hanging wall and footwall blocks to the Gubbedalen Shear Zone (1This study; 2Bowman, 2008; 3Augland, 2007; 4personal communication to Lars E. Augland, 2008; 5Strachan et al., 1995; 6Kalsbeek et al., 1998). 11 Northern Hanging Wall Block The northern hanging wall block to the Gubbedalen Shear Zone is characterized by the Krummedal Sequence, a supracrustal sequence containing Grenvillian and Caledonian rocks and structures. Detrital zircon dates indicate a maximum age of deposition of 1100 Ma, with a major amphibolite-facies metamorphic event at 950 Ma (Strachan et al., 1995; Kalsbeek et al. 1998). Multiple phases of deformation and metamorphism have completely erased pre-existing sedimentary structures. The sequence is known to be roughly 5 to 10 km thick (Higgins, 1988). Compositionally the Krummedal Sequence in the northern study area is mostly a hornblende-biotite-garnet paragneiss folded together with layers of marbles, meta-psammitic rocks (Figure 5A), calc-silicates, and mafic gneisses. The Krummedal Sequence is vertically and laterally a highly variable sequence and correlation between local successions is not possible (Henriksen et al., 2000). Weak gneissic foliation planes measured within the paragneiss record a roughly northwest strike and a moderate northeast dip, and are interpreted to be of Grenvillian origin. In the study area, the Krummedal Sequence has been intruded by two different Caledonian plutons. The Hurry Inlet Granite (Figures 4 and 5B) is a batholith sized non- deformed pluton with two magma pulses occurring at 445 Ma and 438 Ma (Augland, 2007). Sediments of Devonian age are in unconformable contact with the Hurry Inlet Granite (Figure 4). The fairly homogeneous Hodal-Storefjord Monzodiorite (Figures 4 and 5C) has been dated to 424 Ma (Augland, 2007). Cutting across both the Krummedal Sequence and the Hodal-Storefjord Monzodiorite in the northern study area are several NNE-SSW trending, vertical 12 Figure 5. Images of rocks from the hanging wall of the Gubbedalen Shear Zone. A. Krummedal Sequence showing weak gneissic foliation with a metasedimentary biotite schist inclusion. B. Boulder of Hurry Inlet Granite showing lighter felsic injections into a mafic-rich phase with inclusion of coarse-grained granite in the top of boulder. C. Photomicrograph in cross polars of Hodal-Storefjord Monzodiorite showing little internal deformation. D. Lamprophyre dike located within the northern field area. Notice the inclusions of country wall rock within the dike. E. Phlogopite and plagioclase phenocrysts contained within the lamprophyre dike. F. Dolerite dike intruding the Hodal-Storefjord Monzodiorite with contact metamorphic areoles. Notice fining (darkening) of igneous fabric in the dolerite as the contact (in red) is approached. 13 lamprophyre dikes (Figure 4) ranging between 1 and 2 meters wide with prevalent inclusions of host wall rock (Figure 5D). The lamprophyre dikes contain phenocrysts of large (up to 3 cm across) phlogopite grains (Figure 5E). Mantle xenoliths were not observed within the dikes. Cutting the same units as the lamprophyre dikes are 1-2 meter wide dolerite dikes (Figure 5F). The dolerite dikes have contact metamorphic areoles that are 10-20 centimeters thick. These dikes are presumed to be related to Tertiary basalts and can be seen across Hurry Inlet concordantly and discordantly intruding the Jurassic sedimentary rocks of Jameson Land. Eocene flood basalts are the dominant rock unit exposed south of Liverpool Land, across Scoresby Sund (Figure 3) and are known to be related to the opening of the modern Atlantic Ocean. Southern Footwall Block Figure 6 is a lithologic map of the southern field area illustrating rock units of the southern footwall block to the Gubbedalen Shear Zone. A mafic gneiss unit (Figures 4, 6, 7A, and 7B) is structurally the uppermost part of the orthogneiss complex and makes up the lower region of the Gubbedalen Shear Zone. This mafic orthogneiss has a strong gneissic compositional layering (S0) and a lineation (L0) created by the alignment of amphibole and biotite grains (Figure 7B). A felsic orthogneiss unit (Figures 4, 6, 7C, and 7D) lies structurally below the mafic orthogneiss and is the main lithology of the gneissic complex within the southern field area. The felsic unit has the same gneissic banding and mineral aligning lineation of the mafic unit and it carries identical fabrics and structures, indicating synchronous formation. The felsic unit?s gneissosity is composed of alternating layers of quartz and 14 Figure 6. General geologic map of the southern field area depicting the location of the Gubbedalen Shear Zone. Refer to Figure 4 for location of the field area within Liverpool Land. Contour lines are represented as dashed lines (contour interval = 100 meters). Blue lines represent rivers and streams. Blue closed polygons represent lakes. A to A? indicates the location of the cross section produced in Figure 16B. 600m 500m 700m 700m 15 Figure 7. Rocks within the footwall of the Gubbedalen Shear Zone. A. Mafic orthogneiss near the bottom of the shear zone. Note the sheared felsic stringers of quartz and feldspar, sigma clasts indicating tops right in the photo, S2 mylonitic foliation parallels pencil. B. Photomicrograph in plane light of mafic orthogneiss showing S0 gneissic foliation composed of alternating biotite layers with quartz-feldspar layers. C. Felsic orthogneiss preserving S0 gneissic foliation (looking perpendicular to foliation). D. Photomicrograph in plane light of felsic orthogneiss showing S0 gneissic foliation composed of less mafic alternating biotite and hornblende layers with quartz-feldspar layers. E. Highly folded and sheared felsic migmatite. F. Blebby migmatite gneiss with stretched cigar shaped neosomes (looking to the north, parallel to lineation). Note the migmatite foliation S1 sheared into a tops-left mylonitic shear zone in the top of the image. 16 feldspar with biotite and amphibole. Garnet is present within both light and dark layers of the felsic orthogneiss (Figure 7D). The garnet + quartz + feldspar + biotite ? amphibole mineral assemblage of the felsic orthogneiss is indicative of widespread amphibolite-facies retrograde metamorphism within rocks of the footwall to the Gubbedalen Shear Zone. Augland (2007) reports U-Pb zircon data from pegmatites, which based on field relations, he interprets to constrain the age of the amphibolite-facies retrogression to 388 Ma. Evidence of migmatization is widespread within the felsic orthogneiss complex, although none were observed within the mafic orthogneiss (Figures 7E and 7F). Ongoing work by L. Augland (personal communication, 2008) indicates that migmatization was related to the Caledonian event as well. In some migmatites, constrictional strain has elongated the felsic neosomes into cigar-shaped ellipsoids, which are most prominently developed in areas associated with early fold axes (Figure 7F). It was not possible to confidently separate Caledonian metamorphic folia (i.e., gneissosity and schistosity), S1, from Precambrian folia, S0, and thus the author has combined them in S0/S1; likewise, mineral lineations within the orthogneiss and migmatites are combined into L0/L1. Both the mafic and felsic phases of the orthogneiss complex have been cross cut by several generations of granitic veins and dikes. These fine to coarse-grained granitic units have variable orientations and exhibit a stockwork intrusive pattern. These veins and dikes are not observed within the hanging wall block of the Gubbedalen Shear Zone. S0/S1 foliations measured within rocks of the southern field area are plotted on Figure 8. The S0/S1 gneissic foliations are variably striking and have shallow to moderate dips. L0/L1 lineations have mostly north-south orientations and mostly shallow to 17 Figure 8. Geologic map illustrating S 0/S1 foliation planes measured in the southern field area. Inset is a lower hemisphere stereographic projection of poles to S0/S1; n = 22. 18 moderate plunges (Figure 9) with a visually estimated point concentration trending due north and plunging 9?. Stereographic projections document a general domal, to weak north-south trending partial girdle pattern (Figure 8, inset) that defines a fold (?-) axis at N88?E, 5?NE; L0/L1 lineations lie loosely within this great circle. From the foliation and lineation maps and the stereograms, the influence of the Gubbedalen Shear Zone can be seen as all linear and planar fabrics in country rock units in the footwall block are dragged into parallelism with increasing proximity to the shear zone. Although rare mafic and ultramafic bodies exist within the felsic gneiss complex, the main objective of the present study was to clarify the relationship between the country rock hosts and the eclogites (Figures 10A and 10B). Many small (1-5 meter) bodies of pristine and variably retrograded eclogites were observed. The eclogite pods are interpreted to have originated as mafic injections or enclaves that were incorporated into the orthogneiss complex before eclogite-facies metamorphism. The eclogite pods have been internally deformed in a brittle manner, as evidenced by fractures occurring within them (Figure 10A). Felsic melts with large (3 cm) euhedral amphibole crystals are observed filling these fracture openings, and are interpreted to be decompressional melts developed during the exhumation of the eclogites (Figures 10A and 10B). Mylonitic shears (S2) outside of the Gubbedalen Shear Zone and within the orthogneiss footwall block fall into two categories. The first type occur along the margins of boudinaged mafic pods whereas the second type, herein referred to as ?rogue? shears, are not associated with mafic lenses at all but occur randomly throughout the footwall block. These ?rogue? shears are more tabular, subhorizontal mylonitic bodies that are documented to cut S0/S1 foliations within both the mafic (Figure 7A) and felsic 19 Figure 9. Geologic map illustrating L0/L1 lineations measured in the southern field area. Inset is a lower hemisphere stereographic projection of L0/L1 lineations; n = 11. 20 Figure 10. Field images of eclogites and related mylonites within the footwall of the Gubbedalen Shear Zone. A. Boudinaged eclogite pod within the felsic orthogneiss. Note the mylonitization (S2) of the migmatite around the boudin and the presence of felsic veins interpreted to be decompressional melts. B. Eclogite CP-52A with garnet-rich layers (S2, eclogite-facies compositional layering) and felsic decompressional melt veins with large amphibole crystals. 21 (Figure 7F) portions of the orthogneiss complex. They were also observed cutting across granitic veins and dikes. S2 shears along the margins of the eclogite pods are retrogressive, non-coaxial crystal-plastic mylonitic shear zones that have comminuted minerals and obliterated fabrics within their felsic orthogneiss hosts (Figures 10A, 11A, 11B, and 11C). These are generally narrow, 10-30 cm wide shear zones. The mylonitic foliation, S2, is defined by alternating layers of sheared fine-grained quartz, feldspar, and lesser amounts of muscovite, biotite, and amphibole. Quartz and feldspar mostly occur in elongated ribbons and sigma clasts, respectively (Figure 11C) defining a mineral stretching lineation, L2. One particularly well exposed mafic boudin that provided good three-dimensional control of the upper, domal-shaped surface containing S2 and L2 was carefully mapped and analyzed and is illustrated in Figure 11. The S2 mylonitic foliation that wraps over the top of this eclogite boudin is variably striking and has sub-horizontal dips (Figures 11D and 12), reflecting a domal geometry. L2 elongation lineations measured are subhorizontal and trend roughly N50?W/S50?E (Figure 11D). When plotted together with all L2 lineation readings from shear zones wrapping mafic pods and those measured for ?rogue? shears throughout the southern field area (Figure 13B), a conical fold distribution is documented with a cone-axis plunging 21o toward N27oW. Petrographic analysis of mylonites found wrapping the eclogite pods imply that the original mylonite fabric has been partially annealed (Figures 11E and 11F). S-C fabrics, however, are preserved within some of the mylonites. C-planes are defined by recrystallized, strain-free quartz and feldspar ribbons, and S-planes are defined by biotite 22 Figure 11. A. View of a sigmoidal shaped crystal-plastic mylonite wrapping over the top of a small mafic boudin (backpack for scale). B. Line drawing of a mylonite sheathed boudin in A. Solid lines represent mineral elongation lineation and dashed lines represent the vertical joint faces. C. Mylonite (looking perpendicular to foliation and parallel to lineation) from vertical face of a boudin sheathing a mafic lens with large (2.5 cm) potassium feldspar sigma clasts entrained and rotated with tops-right movement. D. Stereogram of data for outcrop shown in A, B, and C, with S2 mylonitic foliation in blue and L2 mineral elongation lineation in black. E. Photomicrograph in cross polarized light of a mylonite wrapping an eclogite boudin. S-C fabric is preserved indicating dextral movement. The shear fabric has been mostly recrystallized and annealed. F. Photomicrograph of myrmekite grains found throughout the boudin wrapping mylonites. 23 Figure 12. Geologic map illustrating S 2 and S3/S4 foliation planes measured in the southern field area. Inset is a lower hemisphere stereographic projection of poles to foliation planes. A. S3/S4 foliations within the Gubbedalen Shear Zone; n = 24. Dashed red line is an average S0/S1 foliation plane. Small circle fit through data (red partial circle) indicates a cone axis at N32?W, 25?W. B. S2 foliations of mylonite shear zones associated with eclogite boudins and ?rogue? shears; n = 14. 24 Figure 13. Geologic map illustrating L 2 and L3/L4 lineations. Inset is a lower hemisphere stereographic projection of elongation lineations. A. L3/L4 lineations within the Gubbedalen Shear Zone; n = 34. Dashed red line is an average S0/S1 foliation plane. B. L2 lineations of shear zones associated with eclogite boudins and ?rogue? shears; n = 25. Small circle fit through data (red circle) indicates a cone axis at N27?W, 19?NW. 25 and lesser amounts of muscovite. Amphibole and garnet have grown within the previously formed mylonitic fabric (Figure 11E). Some feldspar grains have a myrmekitic texture with quartz exsolved out of the interior of grains (Figure 11F). Although no petrographic analysis on ?rogue? shears was performed, they are interpreted to have formed under the same D2 crustal and deformational conditions as the shears encompassing the eclogite pods. This interpretation is based on their similar fault rock types that are derived from the same protoliths and their co-planar and co-linear fabrics. Field relations combined with amphibolite-facies conditions for D2 mylonitization (i.e., dynamic recrystallization of feldspar) require that this shearing post-dated eclogitization. Microstructures indicate that the mylonites stayed at elevated, annealing temperatures during the amphibolite-facies retrogression event that Augland (2008) dated at 388 Ma. D2 shear zones are, therefore, interpreted to have formed in response to non- coaxial simple shearing during exhumation from eclogite-facies conditions to mid-crustal levels. The rigid eclogite bodies apparently were stretched and rotated along a present- day, shallow N50?W/S50?E axis during their ascent into the middle crust. Gubbedalen Shear Zone The Gubbedalen Shear Zone (Figures 4) is the boundary between the northern hanging wall and southern footwall blocks. The shear zone has an east-west trend, dips shallowly to moderately to the north, is approximately 500 meters thick, and records a complex polyphase history. The main lithologies in the lower 400 meters of the shear zone are footwall mafic gneisses and syntectonic felsic granites injected into the shear 26 zone. In the structurally higher levels (upper 100 meters) protoliths are derived from the Krummedal Sequence. The shear zone fabric comprises mylonites, ultramylonites, phyllonites and in the structurally upper most parts cataclasites and breccias. Shear sense indicators within the lower 400 meters of the Gubbedalen Shear Zone record tops-up-to-the-south reverse dip-slip motion. This contractional phase of the shear zone produced mylonitic and ultramylonitic shear fabrics (S3; Figures 14A-C). S-C fabrics and rotated porphyroclasts are the most common shear-sense indicators within mylonites. Mylonitic shears in the Gubbedalen Shear Zone were observed to cut and fold the previously formed gneissosity (S0), migmatitic foliation (S1), and mylonitic shears (S2) in the footwall block documenting tops-south thrust movement (Figure 14C). L3 is defined by pronounced quartz elongation lineations. Microstructures within the mylonites unambiguously confirm the tops-south thrusting. Dextral mica fish with connecting trails of sheared pieces of mica are prevalent within samples from the lower parts of the shear zone (Figure 14D). Sigma type porphyroclasts of single feldspar grains or aggregates of feldspars are common and preserve stepping up-to-the-right dextral geometries (Figure 14E). Feldspars have deformed brittlely by internal fracturing. Slight bulging of grain boundaries within some smaller feldspars and core-mantle structures in larger ones indicate some degree of crystal-plastic deformation. Most quartz within the mylonite has been dynamically recrystallized. Quartz ribbons with prominent subgrains are observed around the margins of competent feldspar porphyroclasts. Mineral assemblages (i.e., quartz + feldspar + biotite + muscovite) and microstructures (i.e., crystal-plastic quartz [~300?C] and crystal- brittle feldspars [~450?C]; Scholtz, 1988; Simpson and Wintsch, 1989) support upper 27 Figure 14. Images and photomicrographs of the contractional lower part of the Gubbedalen Shear Zone. All photos perpendicular to foliation and parallel to lineation. A. Mylonitized migmatitic gneiss and syntectonic granite found within the lower part of the shear zone. B. Mafic-rich ultramylonites with feldspar sigma clasts indicating tops- right (south) thrust movement. C. Ultramylonite (S3) cutting across a mylonitized migmatite (S2), documenting tops-right (south) thrust movement. D. Photomicrograph in cross polarized light from granitic mylonite in image A. Micafish and sigma clasts indicate dextral (tops-up and south) reverse slip movement. Note quartz has subgrains and the shear fabric is dynamically recrystallized. E. Photomicrograph in cross polars from same thin section as D showing a dextral quartz and feldspar aggregate sigma clast. 28 greenschist-facies conditions within the contractional, lower 400 meters of the Gubbedalen Shear Zone. These conditions contrast sharply with the high-temperature annealed mylonites in the footwall (i.e., shears around mafic pods and ?rogue? shears). The upper 100 meters of the Gubbedalen Shear Zone is characterized by tops- north, down-dip, extensional movement. Extensional strains were accommodated in several different fashions. In some places, new mylonites and ultramylonites (S4) formed that cut across the previous S3 mylonitic foliation (Figure 15A). Previous structures have been stretched by this extension. Syntectonic granitic dikes, for instance are excellent markers of this extensional strain (Figure 15B). Extension was largely accommodated parallel to the previously formed contractional structures and fabrics such as those preserved in the lower parts of the Gubbedalen Shear Zone away from the extensional overprint. Numerous reverse-slip crenulations (Figure 15C) and C? shears were observed in outcrops that document tops-north extension of the previously formed S3 mylonitic foliation. Like the structurally lower parts of the shear zone, L4 is defined by a pronounced quartz elongation lineation. The uppermost 20 meters of the shear zone has been chopped by several late-stage, brittle faults marked by carbonate-rich breccias (Figure 15D). Microstructures in rocks collected from within the upper shear zone mylonites also confirm tops-north extensional movement. Quartz ribbons have been pulled, stretched, and rotated (folded) into tops-down-to-the north reverse slip crenulations (Figures 15E and 15F). Subgrains within quartz ribbons preserve S-C composite fabrics indicating down-dip directional movement (Figure 15F). Elongated mica fish are stretched and sheared into a tops-north rotational sense. C? shear bands are common 29 Figure 15. Studies from the extensional overprint in the upper parts of the Gubbedalen Shear Zone. A. Ultramylonitic extensional shear zone (S4) cutting across and retrograding the prior contractional mylonitic fabric (S3). B. S4 extensional shear zone cutting a granitic injection. C. Reverse-slip crenulations documenting tops-down-to-the left (north) extension. D. Carbonate breccia zone at the northern margin of the shear zone in contact with the Hurry Inlet Granite. E. Photomicrograph in plane light of extensional overprint upon the S3 mylonitic fabric. Note the microfolds within the quartz ribbons, and C? shear bands. F. Photomicrograph in cross polarized light of dextral mica fish. Polycrystalline quartz ribbons contain sugbrains and recrystallized grain shape preferred orientation documenting sinistral extensional shear. 30 tops-north extensional shear indicators (Figure 15E). Brittle deformation of feldspar is indicated by microfaults and fractures (Figures 15E and 15F). Much more biotite occurs within the mylonites in the upper parts of the shear zone, which is interpreted to reflect incorporation of Krummedal Sequence metasedimentary rocks; Figures 15E and 15F could be referred to as phyllonites. The presence of crystal-plastic quartz and crystal- brittle feldspar within the upper part of the Gubbedalen Shear Zone documents a deformational temperature around ~300?C, indicating lower greenschist-facies conditions. The D4 structures and fabrics are interpreted to reflect further exhumation of the footwall and its mylonitic carapace into the upper crust and then to near Earth surface conditions to form the latest-stage brittle faults and carbonate breccias. The mylonitic and ultramylonitic foliations (S3/S4) and mineral elongation lineations (L3/L4) measured within the Gubbedalen Shear Zone are plotted on Figure 12 and Figure 13, respectively. Stereographic projections of S3/S4 mylonitic foliations indicate that the shear zone is east-west trending (Figure 12, Inset A), and L3/L4 mineral stretching lineations are almost exclusively down-dip to the north (Figure 13, Inset A). The Gubbedalen Shear Zone affects footwall block rocks for at least 1 kilometer structurally beneath the main zone of mylonites. Figure 16 is a composite figure including a profile across the shear zone documenting its widespread affects. Gneissosity (S0), migmatitic foliations (S1), and the brittle stockwork of granitic veins have been rotated into parallelism with the shear zone. Mineral lineations (L0), stretched neosomal ?cigars? (L1), and mineral elongation lineations (L2) have been elongated and stretched within the shear zone parallel to L3/L4. 31 Figure 16. A. Photo mosaic of the Gubbedalen Shear Zone (outlined in red) looking to the east along a valley wall. Extensional and contractional zones are separated by the blue line. B. Schematic cross section from A to A? of the Gubbedalen Shear Zone and surrounding terranes (location of cross section marked in Figure 6). Shear couples within the shear zone represent the direction of shear. Straight lines represent the mylonitic foliation and wavy lines represent the migmatitic foliation. C. Felsic dikes within the bottom of the shear zone (looking north) pulled into parallelism with the shear zone?s foliation. D. Unaffected felsic dikes from a canyon wall (looking east) well south of the shear zone. 32 Figure 17 is summarizes all the structural data that was collected within the southern field area. Figure 17A plots gneissosity (S0), migmatitic foliation (S1), and mylonitic foliation (S2). A great circle fits through the data, indicating that the Gubbedalen Shear Zone is a monocline with an axis oriented N88?E, 4?NE (Figure 16B); this monoclinal style for the hinge to the shear zone is expressed in the cross section in Figure 16B. Figure 17B depicts mineral alignment (L0), neosomal ?cigars? (L1), and elongation lineations (L2). A small circle fits through the data indicating the axis of a cone at N27?W, 21?NW. This cone axis likely reflects sheath fold geometries created by the Gubbedalen Shear Zone as rock fabric and structures of the footwall are swept into it. Another trend indicated in Figure 17B is that lineations trend progressively more toward the northwest as the dip of foliation shallows. As described above for the investigated shear zones illustrated in Figure 11A through 11D, it appears that the eclogite-pod and ?rogue? shears initiated with a more easterly-westerly trend that was rotated about this conical fold axis. Data are also skewed toward a preponderance of readings from the domal crest of the Liverpool Land eclogite-containing core, as the Gubbedalen Shear Zone projects just above the footwall block of the southern study area. In other words, the data are skewed towards more contractional measurements from the basal parts of the Gubbedalen Shear Zone reflecting the contractional history that may have been directed more towards the southeast rather than due south. 33 Figure 17. A. Stereographic projection of poles to planes from all foliation data (S0, S1, S2, S3, and S4) collected in the southern field area. B. Stereographic projection of all lineations (L0, L1, L2, L3, and L4) collected in the southern field area (n equals the number of measurements) 34 III. PETROLOGY AND PETROGRAPHY OF ECLOGITES Petrography Three eclogite samples (CP-47, CP-52A, and CP-92) were chosen for petrologic and petrographic analyses due to their differing levels of retrogression (Figure 18). The samples contain two mineral assemblages, one equilibrated under eclogite-facies and then a later one that was retrogressed to granulite-facies conditions. The eclogite-facies assemblage contains garnet + omphacite + quartz ? zircon ? rutile ? illmenite. The granulite-facies assemblage is garnet + low-sodium clinopyroxene + plagioclase + amphibole + quartz. Samples CP-47 and CP-92 both include pyroxene-plagioclase- amphibole symplectites. The symplectites formed after the breakdown of omphacite during decompression and can be used to infer prior, peak eclogite-facies conditions (Anderson and Moecher, 2007). Some mafic pods within the field area contain an amphibolite-facies retrogression assemblage, but this study focused on more pristine eclogite samples. Sample CP-52A (Figure 19A) is the most pristine and least retrograded eclogite sample. CP-52A contains light pink, heavily fractured, hypidioblastic garnets that have inclusions of quartz, zircon, rutile, monazite, and sparse omphacite. Quartz inclusions do not exhibit radial fracture patterns around the inclusions, which might be indicative of ultra-high pressure metamorphism. Hypidioblastic omphacite grains have a slight pale 35 Figure 18. Simplified geologic map showing the location of eclogite samples that were petrographically and chemically analyzed (CP-47: 70? 34.937?N, 22? 13.770?W; CP-52A: 70? 34.633?N, 22? 15.220?W; and CP-92: 70? 35.362?N, 22? 12.106?W). 36 Figure 19. A. Eclogite CP-52A in plane light, notice the thin rim of retrograde hornblende growing on the omphacite grain. B. Eclogite CP-92 in plane light with fine- grained lamellar plagioclase-clinopyroxene-hornblende symplectites. C. Zoomed in Back Scatter Electron image of the area depicted in B. D. Eclogite CP-47 in plane light showing coarse grained wormy plagioclase-clinopyroxene-hornblende symplectites. E. Back Scatter Electron image of sample CP-47 (field of view is ~1 cm). F. Quartz exsolution rods within remnant omphacite grain and small low-sodium clinopyroxene nucleating in plagioclase within sample CP-47 in plane light. Abbreviations used in figure. Grt = Garnet, Cpx = low-Na clinopyroxene, Qtz = quartz, Plag = Plagioclase, Zr = Zircon, Omp = Omphacite, Hbl = Hornblende. 37 green pleochroism and are also heavily fractured. Omphacite cores are still pristine, but grain boundaries are retrogressed into hornblende. Sample CP-92 (Figure 19B and 19C) is heavily retrogressed and contains few relict grains from the prograde mineral assemblage. Garnets are light pink, hypidioblastic, but not as heavily fractured as sample CP-52A. Garnets contain fewer inclusions of zircon, rutile, and monazite than CP-52A. Omphacite has been replaced by fine grained symplectites of lobate low-sodium clinopyroxene, plagioclase, and hornblende, and have a slight lamellar texture. Each symplectite is rimmed with a corona of quartz and plagioclase. Prograde quartz is more abundant in CP-92 than in CP-52A. Sample CP-47 has the same mineral assemblage as sample CP-92 but the symplectites have a very different texture. Symplectites have a wormy texture and are coarser grained than CP-92. Symplectic-grain cores still preserve richer omphacite compositions, but the edges of the symplectites are dominated by low-sodium pyroxenes and amphiboles (Figure 19D and 19E). Pyroxene grains contain quartz rods that have exsolved from the pyroxene, and very fine grained pyroxenes have nucleated in the plagioclase portions of the symplectites (Figure 19F). Both of these features demonstrate the mineral assemblages attempted to reach equilibrium as the rock was retrograded. Mineral Chemistry Mineral compositions for garnet, pyroxene, plagioclase, and amphibole were determined using quantitative Wavelength-Dispersive System (WDS) microprobe analysis. Table 2 contains averaged mineral compositions for garnet, pyroxene, plagioclase, and amphibole for all eclogite samples. Data from all microprobe analyses 38 are in Appendix B. Garnet formulae were recalculated based on 12 oxygens, pyroxene on 6 oxygens, plagioclase on 8 oxygens, and amphibole on 23 oxygens. Fe2+ and Fe3+ of garnet and pyroxene were estimated by stoichiometry (Droop, 1987); all Fe for plagioclase and amphibole were assumed to be Fe2+. S am pl e CP - 47 CP - 52 A CP - 92 CP - 47 CP - 52 A CP - 92 CP - 47 CP - 52 A CP - 92 CP - 47 CP - 52 A CP - 92 n 10 9 5 14 11 12 17 1 10 5 1 5 S i O2 39.22 39.49 39.05 50.47 53.74 50.26 59.82 68.56 63.48 43.72 41.30 41.30 T i O2 0.06 0.08 0.07 0.29 0.28 0.31 0.00 0.01 0.00 1.38 0.51 1.33 A l 2O 3 22.17 22.29 21.82 3.92 12.35 7.03 25.23 19.88 23.09 11.45 15.47 14.32 Cr 2O 3 0.01 0.00 0.01 0.02 0.01 0.01 0.01 0.00 0.01 0.01 0.00 0.01 F eO 19.58 18.62 22.23 10.32 4.81 10.53 0.21 0.11 0.23 14.07 11.77 13.65 M nO 0.30 0.21 0.36 0.11 0.03 0.12 0.01 0.07 0.01 0.06 0.06 0.09 M gO 7.60 7.76 6.64 12.28 8.41 10.60 0.00 0.00 0.00 12.22 13.23 12.21 CaO 11.17 11.98 10.29 21.57 15.08 19.17 7.32 0.32 4.44 11.61 11.10 11.31 Na2 O 0.02 0.01 0.05 0.61 5.61 1.94 7.44 11.56 9.28 1.68 2.65 3.13 K 2O 0.01 0.00 0.00 0.01 0.00 0.00 0.23 0.06 0.01 0.54 0.90 0.02 T ot al 100.16 100.45 100.53 99.60 100.33 99.98 100.29 100.57 100.57 96.75 96.99 97.38 Si 2.977 2.980 2.983 1.893 1.917 1.865 2.663 2.981 2.793 6.519 6.114 6.136 Ti 0.004 0.005 0.004 0.008 0.007 0.009 0.000 0.000 0.000 0.155 0.057 0.149 Al 1.983 1.983 1.964 0.173 0.519 0.307 1.324 1.019 1.198 2.013 2.700 2.508 Cr 0.001 0.000 0.001 0.001 0.000 0.001 0.000 0.000 0.001 0.004 0.000 0.004 T ot al F e 1.243 1.175 1.420 0.323 0.144 0.327 0.008 0.004 0.009 1.754 1.456 1.696 Mn 0.019 0.013 0.023 0.003 0.001 0.004 0.001 0.003 0.001 0.008 0.007 0.011 Mg 0.860 0.873 0.756 0.686 0.448 0.587 0.000 0.000 0.000 2.716 2.921 2.704 Ca 0.909 0.968 0.842 0.867 0.577 0.762 0.349 0.015 0.210 1.854 1.760 1.800 Na 0.003 0.002 0.007 0.044 0.387 0.139 0.642 0.975 0.791 0.487 0.762 0.902 K 0.001 0.000 0.000 0.000 0.000 0.000 0.013 0.003 0.000 0.104 0.170 0.004 T ot al 8.000 8.000 8.000 4.000 4.000 4.000 5.002 4.999 5.003 15.613 15.946 15.913 n - n um be r o f an al yses ave r ag ed G a r n e t P y r o x e n e P l a g i o c l a s e A m p h i b o l e Table 2. Table contains averaged weight percent oxides from multiple (n = number) microprobe analyses of garnet, pyroxene, plagioclase, and amphibole. The three eclogite samples had garnets with very similar average compositions of Alm+Sps42Grs30Prp28 for CP-47, Alm+Sps39Grs32Prp29 for CP-52A, and Alm+Sps47Grs28Prp25 for CP-92 (Figure 20). The differing garnet compositions between samples can be contributed to bulk composition, as opposed to chemical changes due to retrograde metamorphism. Elemental mapping of garnets show homogenous cores without zoning, indicating complete equilibrium at eclogite-facies conditions. There are slight differences in the iron and magnesium contents at grain boundaries with pyroxene as a result of re-equilibration during the retrograde event. 39 Figure 20. End member compositions of analyzed garnet grains from eclogite samples displayed on a ternary diagram (after Coleman et al., 1965). Fe32+Al2Si3O12 + Mn3Al2Si3O12 Ca3Al2Si3O12 Mg3Al2Si3O12 30 Mol.% 55 Mol. % Sample CP-52A Sample CP-47 Sample CP-92 40 Compositions of minerals other than garnet change dramatically between the pristine and retrograde eclogites. Pyroxenes from the most pristine eclogite (CP-52A) plot in the omphacite field on the ternary diagram, whereas pyroxenes that make up the symplectites (CP-47 and CP-92) plot in the Quad end of the diagram (Figure 21). As omphacite chemically breaks down to form the symplectites, sodium is released from pyroxene and is accommodated by plagioclase, as seen in element maps where sodium is depleted at the grain boundary (Figure 22). The amphiboles are calcium and sodium-rich and belong to the hornblende group. Amphibole compositions were plotted on a silicon versus sodium plus potassium diagram (Figure 23), and are more Edenite and Pargasite- rich, which are higher temperature and pressure amphiboles. Geothermobarometry Eclogite sample CP-52A was chosen for geothermobarometric calculations because the sample contains the most pristine eclogite-facies assemblage. Microprobe analysis was performed on six pairs of garnet and omphacite grains. The cores of adjacent grains were analyzed, because they should preserve the peak pressure and temperature conditions of eclogitization. The following sections describe the calculations necessary for determining the P-T conditions. Thermometry Calculations The traditional Ellis and Green (1979) calibration of the Fe-Mg exchange thermometer between garnet and clinopyroxene could not be used. The grossular content of the garnets being used for geothermometry was upwards of 30%. The calibration of 41 Figure 21. End member compositions of analyzed clinopyroxene grains from eclogite samples displayed on a ternary diagram (after Morimoto et al,. 1988). NaAlSi2O6 (Jd) NaFe3+Si2O6 (Ac) Jadeite Aegirine Aegerine-Augite Omphacite Quad Wo, En, Fs Sample CP- 52A Sample CP- 47 Sample CP- 92 42 Figure 22. Element maps of calcium (left) and sodium (right) of eclogite CP-52A, with lighter colors being more enriched in the element. The central grain is an omphacite with a garnet grain to the top left of each image. Notice the fine grained symplectite that is forming along fractures within the omphacite. Image is approximately 1 cm. Figure 23. End member compositions of analyzed amphibole grains from eclogite samples on a Silicon versus Na+K diagram (after Deer et al., 1992). Edenite Pargasite Tremolite Hornblende Tschermakite Sample CP- 52A Sample CP- 47 Sample CP- 92 43 the Ellis and Green (1979) thermometer is not suited for calcium levels that high, and the newer updated calibration of Krogh Ravna (2000) was used. The peak temperature of the eclogite-facies event was estimated using the garnet-clinopyroxene Fe2+- Mg exchange thermometer according to the following mineral reaction (Ellis and Green, 1979): 3 Diopside + Almandine = 3 Hedenbergite + Pyrope The P-T compositional relationship was determined by the following equation (Krogh Ravna, 2000): XXXXX G r tMgG r tMnG r tMnG r tCaG r tCaCT #22 1105)(35353319)(139632709.1939[()( ? 3#2# )(2 3 2 4)(3 5 6 1 XX G r tMgG r tMg 2 7 3)]2 2 3.1/ ( l n))(4.1 6 9 DKG P aP where KD = (Fe2+/Mg)Grt/(Fe2+/Mg)Cpx, XGrtCa = Ca/(Ca + Man + Fe2++Mg) in garnet, XGrtMn = Mn/(Ca + Man + Fe2++Mg) in garnet, and XGrtMg# = Mg/(Mg+Fe2+) in garnet. Temperature calculations were based on the procedures outlined in Krogh Ravna (2000) and further information on the Fe-Mg thermometer can be found therein. Barometry Calculations Due to the absence of orthopyroxene in the eclogite-facies assemblage, absolute pressures of formation could not be estimated using a two pyroxene system. However, minimum pressures of formation could be calculated using the Jadeite component of omphacite grains following the equilibrium reaction: Albite = Jadeite + Quartz 44 The P-T compositional relationship was determined by the following equation (Holland, 1980): PCTP )(0 2 6 5.035.0 ? where pressure is in kbars and P is a pressure correction based on the Jadeite content of the clinopyroxene. The value of P is given by the equation (Holland, 1980): JdVRTP ln)/( ? where R is the gas constant, T is the absolute temperature of formation, the volume change of the reaction, ?V , was found to be 1.734 J/bar, and Jd is the activity of Jadeite in the pyroxene. The activity of Jadeite is given by (Holland, 1979): JdJdJd X 2 where XJd and Jd are the mole fraction and activity coefficient of Jadeite, respectively. The activity of Jadeite was determined by (Holland, 1979): ])1)(/e x p [ ( 2X JdJd RTW where the interaction energy, W, was found to be 24 KJ. Pressure calculations were based on the previous equations and procedures outlined in Holland (1979; 1980) and further information on the albite = jadeite + quartz reaction can be found therein. Results Calculations from the aforementioned thermometry and barometry sections are summarized in Table 3. The Pressure-Temperature equations were simultaneously solved using an Excel? spreadsheet developed by the author using 100 iterations and a tolerance of 0.001. A mean temperature of ~867?C and a minimum pressure of 18.2 45 kbars were estimated for the peak of eclogite formation. These conditions constrain the metamorphism to high pressure conditions, in contrast to the ultra high pressure conditions reported in the abstract by Hartz et al. (2005). High pressure eclogitization in Liverpool Land also contrast with the ultra high pressure event documented in the North Eastern Greenland Eclogite Province (Gilotti and Ravna, 2002), further to the north of the study area. Pressure - Temperature Calculations Grt-Cpx Pair #1 #2 #3 #4 #5 #6 XGrtCa 0.3220 0.3336 0.3244 0.3221 0.3266 0.3283 XGrtMn 0.0043 0.0051 0.0042 0.0046 0.0055 0.0048 XGrtMg# 0.4392 0.4330 0.4382 0.4329 0.4428 0.4556 KD 4.8285 4.8927 4.5103 5.3906 5.4011 3.9290 XCpxJd 0.3790 0.3702 0.3810 0.3861 0.3731 0.3792 ?Jd 2.7204 2.7815 2.6330 2.7584 2.8760 2.5215 ?Jd 0.3908 0.3812 0.3823 0.4113 0.4004 0.3626 P (kbar) 18.07 18.09 18.73 17.31 17.19 20.00 T (?C) 857.72 864.73 892.24 812.32 813.35 962.39 Table 3. Summary table of geothermobarometric calculations. 46 IV. 40Ar/39Ar GEOCHRONOLOGY OF LAMPROPHYRE DIKES Samples M-14C and M-21 are from two NNE-SSW trending lamprophyre dikes in Figure 4. Sample M-14C (70? 52.644?N, 22? 20.091?W) was collected near to where the lamprophyre intruded the contact between the Krummedal Sequence and the Hodal- Storefjord Monzodiorite pluton. Sample M-21 (70? 52.696?N, 22? 17.493?W) was collected where the lamprophyre intruded the Hodal-Storefjord Monzodiorite pluton. The two lamprophyre sampling locations are approximately 0.75 kilometers apart. Petrography Sample M-14C contains euhedral phenocrysts of plagioclase and phlogopite with very sharp grain boundaries and little to no alteration (Figure 24A). Phlogopite crystals are strongly pleochroic, changing from a tan-brown to colorless in plane light. Minor inclusions of plagioclase within the phlogopite are common. Phlogopite grains have very prominent mica cleavage traces. Some phlogopite grains may have a radial crystal form, which can be explained by the crystal being cut by the thin section at an odd angle, due to the large size of the phenocrysts. Compositional zoning is ubiquitous in plagioclase phenocrysts (Figure 24B). The matrix comprises very fine grained phlogopite, sodium plagioclase, and opaque minerals. Calcite can be seen filling late stage cracks with the matrix and in the interior portions of some mineral grains. Sample M-21 (Figure 24C) contains the same mineral assemblage as the M-14C lamprophyre. The only difference 47 Figure 24. A. Photomicrograph in plane light from sample M-14C of euhedral phologopite and plagioclase phenocrysts within a matrix of phlogopite, plagioclase, and opaques (in images Phl = phlogopite and Plag = plagioclase). B. Optically zoned plagioclase phenocryst within M-14C (cross-polarized light). Steel blue birefringence of the plagioclase is believed to be a result of the thin section being slightly too think. C. Phlogopite and plagioclase phenocrysts within M-21 (plane light). Note the radiogenic halo within the tan-brown phlogopite grain in contact with matrix feldspar (lower right). 48 between the two samples is the matrix of M-21 contains less opaque minerals than M- 14C and contains small amounts of chlorite. The presence of phlogopite phenocrysts and sodium plagioclase within the matrix makes both of these lamprophyres of the Kersantite variety. 40Ar/39Ar Methods The lamprophyre samples were crushed and approximately 50 phlogopite grains were picked from each sample using a binocular microscope and were prepared for 40Ar/39Ar analysis in the Auburn Noble Isotope Mass Analysis Laboratory (ANIMAL). Both Single Crystal Total Fusion (SCTF) and Incremental Heating (IH) techniques were used to analyze the phlogopite grains in order to check for consistency between the methods. Nine grains from each sample were analyzed using SCTF and one grain from each sample was analyzed using IH. Further information concerning 40Ar/39Ar methods and raw data are included in Appendix C. 40Ar/39Ar Results The IH analyses for sample M-14C provide a plateau age of 261.56?0.38 Ma (calculated with 1? error and a 95% confidence level; Figure 25) with 96.9% of the total 39ArK released. IH analysis was performed for sample M-21, and the data yield a plateau age of 263.93?0.93 Ma (Figure 26) with 97.1% of the total 39ArK included. The SCTF analyses all yielded very consistent ages grouping around the plateau age dates. For both samples, the probability that the SCTF data was part of a normal distribution was 0.00%, showing that the age variations seen in the data are due to differences in the age of 49 Figure 25. Plateau diagram produced from the incremental heating data collected from sample M-14C. Inset. Probability density diagram created from the SCTF data from sample M-14C. Individual crystal data represented as points with error bars (error bars are1?). Prob. = the probability that the SCTF data could be part of a normal distribution. M - 1 4 C P l a t e a u A g e 100 200 300 400 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C u m u l a ti v e 39 A r F r a c ti o n A g e (M a ) P l a t e a u a g e = 2 6 1 . 5 6 ? 0 . 3 8 M a (1 , i n cl u d i n g J- e r r o r o f . 0 0 0 0 0 0 1 % ) M S W D = 1 . 7 , p r o b a b i l i t y = 0 . 0 9 5 I n cl u d e s 9 6 . 9 % o f t h e 39 Ar P l a t e a u s t e p s a r e m a g e n t a , r e j e c t e d s t e p s a r e c y a n b o x h e i g h t s a re 1 256 258 260 262 264 M-14C Prob = 0.00% 50 Figure 26. Plateau diagram produced from the incremental heating data collected from sample M-21. Inset. Probability density diagram created from the SCTF data from sample M-21. Individual crystal data represented as points with error bars (error bars are1?). Prob. = the probability that the SCTF data could be part of a normal distribution. M - 2 1 P l a t e a u A g e 100 200 300 400 0 . 0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 C u m u l a ti v e 39 A r F r a c ti o n A g e (M a ) P l a t e a u a g e = 2 6 3 . 9 3 ? 0 . 3 7 M a (1 , i n cl u d i n g J- e r r o r o f . 0 0 0 0 0 0 1 % ) M S W D = 0 . 9 6 , p r o b a b i l i t y = 0 . 4 5 I n cl u d e s 9 7 . 1 % o f t h e 39 Ar P l a t e a u s t e p s a r e m a g e n t a , r e j e c t e d s t e p s a r e c y a n b o x h e i g h t s a re 1 M-21 258 260 262 264 266 268 Prob = 0.00% 51 individual crystals and not internal analytical error. Linear regression of the SCTF data showed no correlation and a tight clustering of data. These results are taken to indicate that extraneous argon is not present in the phlogopite mineral grains analyzed. The results of the laser SCTF and IH analyses for samples M-21C and M-21 are interpreted to indicate lamprophyre crystallization at ca. 262 and 264 Ma. 52 V. DISCUSSION To synthesize the tectonic evolution of rocks exposed in Liverpool Land, results from the present study are combined with data from other members of the 2006 expedition, summarized in Table 1. The Gubbedalen Shear Zone is herein interpreted to be essentially a detachment fault along a Caledonian metamorphic core complex (Coney, 1980). As such, the geologic history of the hanging wall is less important to understanding the evolution of the metamorphic core; this is why work was concentrated in the southern map area. Hanging wall block evolution during the Caledonian is linked to the intrusion of the calc-alkaline Hurry Inlet Granite with pulses at 445 and 438 Ma, and the intrusion of the Hodal-Storefjord Monzodiorite at 424 Ma (Augland, 2007). The orthogneiss terrane of the footwall block to the Liverpool Land metamorphic core complex has a much more varied and significant history in regards to Caledonian evolution than the hanging wall block. The protolith age of the orthogneiss in the footwall is not well dated. An upper intercept age of 1660 Ma on zircons separated from one of the eclogites is interpreted as the time of crystallization for mafic bodies intruded into the gneissic complex (Augland, 2007). Likewise, the first deformational event (D0) recorded within the footwall block is not absolutely dated. D0 must occur after the emplacement of mafic bodies within the footwall at 1660 Ma, but before Caledonian migmitization (S1) that overprints the gneissic foliation (S0) of the felsic orthogneiss terrane, placing minimum and maximum ages on the timing of deformation. 53 During D1, the southern Liverpool Land orthogneiss complex was tectonically buried as the Caledonian orogenic welt grew, initializing migmatization of the orthogneiss (L. Augland, personal communication, 2008). As the footwall block orthogneisses were brought deeper into the crust they reached eclogite-facies conditions (middle D2 in Table 1) at 399 Ma (Augland, 2007). Results of the present study estimate peak eclogite-facies conditions were achieved at ~867?C and >18.2 kbars, representing a burial depth of approximately 70 kilometers. Syn-collisional normal faulting is a possible mechanism for exhumation of the high pressure orthogneiss terrane during continental subduction (Figure 27: Chemenda et al., 1995; Chemenda et al., 1996). The continental slab is subducted to a maximum depth, which is proportional to the strength of the crust and inversely proportional to the pressure within the plate created by collision. At maximum depth, the crust fails and imbricates, allowing for buoyancy driven uplift of a subducted crustal slice, as the rest of the lithospheric slab continues to subduct. This uplifting creates reverse movement along the bottom contact of the crustal slice and down-going lithosphere and the appearance of normal movement along the contact of the crustal slice and overriding plate (Chemenda et al., 1995; Chemenda et al., 1996). It appears that the orthogneiss terrane is an uplifted crustal slice that delaminated from the down-going lithosphere; however, the normal fault that brought the eclogite-containing orthogneiss terrane to the surface is not observed within Liverpool Land. This normal fault would have been positioned at a high structural level and may have been cut out by the Gubbedalen Shear Zone or possibly by other post- Caledonian faulting that has segmented and chopped the orogen (Figure 3: Haller, 1985). 54 Figu re 27 . A. Subduc tio n of the B alt ic lit hosphe ric slab unde rne ath La ure nti a during conti ne ntal subduc tion. B. Fa ilur e of the uppe r c rust afte r re achin g e clogi te- fac ies c ondit ions , re sult ing i n the uplift of a crusta l sl ice (or thogn eiss footwa ll ter ran e), cre ati ng a se nse o f no rma l m ove ment a long t he co ntac t wit h the ove rridi ng plate . X? s re pre sent brit tle fa ult ing occ urring in t he ove rridi ng La ure nti an c rust. C. C onti nu ed upli ft of the c rusta l sl ice to sh allow c rusta l le ve ls (modi fied f rom Cheme nda et al. , 1995) . 55 The Liverpool Land eclogites share a great number of similarities with eclogites of the Western Gneiss Region of Norway, leading the author to suggest that the former may be an orphaned block of the latter that was sutured onto the Laurentian margin, corroborating the idea that the orthogneiss footwall terrane is a crustal slice from the down-going Baltic slab. Paleogeographic reconstructions (Blakey, 2007; Bowman, 2008) depict the Western Gneiss Region adjacent to Liverpool Land during the Silurian collision with Baltica. Eclogites in both regions occur as boudinaged mafic pods within a felsic orthogneiss complex (Dunn and Medaris, 1989). Protolith ages for the eclogites in Liverpool Land and the Western Gneiss Region are comparable (~1660 Ma: Root et al., 2004; Augland, 2007). Likewise, the country rocks of both terranes include ultramafic rocks that are absent outside of the eclogite-bearing terranes (Smith and Cheeney, 1981; Brueckner, 1998). The timing of eclogitization in both regions is also of comparable age (~399 Ma; Root et al., 2004; Augland, 2007). Liverpool Land eclogites are herein found to have formed at temperature and pressure conditions of approximately 867?C and >18.2 kbars. Dunn and Medaris (1989) report Western Gneiss Region eclogites found at ~800?C and > 18-19 kbars. Eclogite-facies mineral compositions also are comparable, and they have very similar coarse-grained wormy symplectites of low-sodium clinopyroxene, plagioclase, and amphibole, after the decompression breakdown of omphacite. All the above mentioned similarities lead the author to interpret that the southern orthogneiss terrane of Liverpool Land is a crustal slice of the Western Gneiss Region left behind in East Greenland. During the exhumation of southern Liverpool Land, the orthogneiss terrane was brought through granulite-facies conditions (middle D2) as recorded by the eclogite 56 symplectites. Upon further exhumation, late D2 deformation produced mylonitic shears wrapping the eclogite pods as well as the ?rogue? shears in the footwall block. The footwall terrane was brought up rapidly to middle-crustal levels where amphibolite-facies metamorphism at approximately 388 Ma (Augland, 2007) caused partial annealing of the fabrics within the mylonites. Wormy low-sodium clinopyroxene-plagioclase-amphibole symplectites like those in the Liverpool Land eclogites have been documented in other continental eclogites and interpreted to have formed due to rapid exhumation (Anderson and Moecher, 2007). D3 marks a renewed pulse of contraction along the Gubbedalen Shear Zone, which emplaced the orthogneiss footwall block against the hanging wall block containing the Krummedal Sequence and the Caledonian plutons. D3 contraction likely cut out the earlier normal fault that exhumed the eclogite-containing orthogneiss terrane. Syntectonic dikes within the Gubbedalen Shear Zone, dated to ~386 Ma (Augland, 2007), likely injected at the beginning of contractional D3 shearing. Extensional movement along the Gubbedalen Shear Zone is recorded by D4 structures. Extensional faults commonly overprint, or reactivate, previously formed thrust faults and have been documented in other parts of East Greenland (Strachan, 1994). Last movements along the Gubbedalen Shear Zone occurred at 380 Ma as dated by 40Ar/39Ar analysis of muscovite recovered from rocks within the shear zone (Bowman, 2008). This timing for extensional faulting is synchronous with other Devonian-aged detachment faults within both the East Greenland and Norwegian Caledonides (Figure 28; Braathen et al., 2000; Hartz et al., 2002; Ebbing et al., 2006), and is compatible with 57 Figure 28. Devonian detachment faults within the East Greenland and Scandinavian Caledonides (Ebbing et al., 2006). 58 Devonian Sediments having been deposited onto the Hurry Inlet Granite within the hanging wall block of the Gubbedalen Shear Zone (Figure 4). Lamprophyres in the northern field area record another pulse of extension within East Greenland that occurred during the Late Permian (~262 and ~264 Ma), synchronously with deposition of Permian clastic sediments in Liverpool Land (Figure 3). Paleogeographic plate reconstructions position Liverpool Land near the Lofoten region of north Norway at this time (Figure 29; Blakey, 2007) when the Lofoten metamorphic core complex was forming (Steltenpohl et al., 2004). 40Ar/39Ar data from both regions overlap on a probability density diagram (Figure 30), implying that Permian extension was occurring on both sides of the orogen as well as further south (i.e., Oslo Rift; Wilson et al., 2004). Sedimentation continued to occur in the region, filling the Triassic and Jurassic basins of Jameson Land to the west of Liverpool Land (Figure 3). Finally, Eocene rifting emplaced basaltic sills and dikes into the Jameson Land sedimentary basins. This rifting covered the southern Scoresby Sund landscape with large volumes of flood basalts (Figure 3). Alternate Explanation of Liverpool Land Eclogites To explain the occurrence of eclogites in the Laurentian upper plate of the Caledonian collisional zone, Hartz et al. (2005) suggested that the Liverpool Land eclogites can not be simply attributed to metamorphic processes due to overburden (i.e., pressure to depth relationship). Later, Hartz et al. (2007) hypothesized that eclogite formation was due to the effects of tectonic overpressure, introducing a new theoretical concept of ?reaction overpressure.? 59 Figure 29. Paleogeographic plate reconstruction during the Permian (~260 Ma) showing the Liverpool Land region (red star) against Lofoten, Norway (blue star; Blakey, 2007). 60 Figure 30. A and B. Location of the Lofoten Islands of northern Norway (Steltenpohl et al., 2004). C. Probability density diagram with hydrothermal muscovite age from Lofoten fault zone in black (data from Steltenpohl et al., 2004) and phlogopite crystallization age from Liverpool Land lamprophyres in blue and red. D. Diagram depicting the Permian metamorphic core complex of Lofoten (Steltenpohl et al., 2004). 61 Tectonic overpressure is the concept that within a convergent tectonic setting, pressure can be considerably higher than lithostatic (pressure = density x gravity x depth). Tectonic overpressure is theoretically created by plate tectonic derived horizontal stresses coupled with flexural vertical loads caused by the deflection of the upper crust and lower mantle during collision (Petrini and Podladchikov, 2000). ?Reaction overpressure? as hypothesized by Hartz et al. (2007) is based on the same principle as a pressure cooker. It requires a rock inclusion enclosed in a stronger rock container. As the inclusion is heated, it will start to expand creating ultra-high pressures. When pressures exceed the strength of the container, it will fracture, and Hartz et al. (2007) predicted that the mafic inclusion will show evidence of decompressional melting. Field observations from this study indicate that tectonic overpressure is not necessary to account for the formation of the eclogites in Liverpool Land. First, the concept of ?reaction overpressure? can be dispelled by considering the eclogite-bearing host rocks. In the study area, the eclogite container was the felsic orthogneisses, which were not at all strong and rigid during eclogitization. In all observed cases, the orthogneiss around the eclogite boudins behaved in a plastic manner, resulting in migmatites and mylonites. There are decompressional melts originating within the eclogite pod themselves, but these are more parsimoniously explained by rapid tectonic exhumation of the eclogite terrane. Second, Hartz et al. (2007) presumed that the Liverpool Land eclogite terrane was positioned in the overriding plate of the Caledonian collision, a concept that is challenged by the model for tectonic evolution of the orthogneiss footwall terrane as described in this study. 62 VI. CONCLUSIONS Field studies and laboratory analysis on rocks in southern Liverpool Land, East Greenland provide new constraints on Caledonian tectonic evolution in an important area where very little was previously known. Key contributions to this understanding that resulted from the present study are summarized below. ? The relative deformational sequence contained in rocks of Liverpool Land (Table 1) has been constrained for the first time. By combining this relative sequence with previous, ongoing, and new isotopic work reported herein, the absolute sequencing of metamorphic and deformational episodes has also been outlined for the first time. ? The Gubbedalen Shear Zone was discovered and documented by the 2006 expedition team. Work presented herein documents that the Gubbedalen Shear Zone is a greenschist-facies, east-west trending, shallowly to moderately north- dipping shear zone that is approximately 500 meters thick. The lower 400 meters of the shear zone records tops-up-to-the-south reverse dip-slip motion, and the upper 100 meters is characterized by tops-north, down-dip, extensional movement. ? Little had been published about the petrography and pressure-temperature conditions of eclogite-facies metamorphism within rocks of Liverpool Land. Geothermobarometric calculations conducted using microprobe data determined 63 that peak conditions of eclogitization occurred at ~867?C and >18.2 kbars. Petrographic studies document granulite-facies symplectic replacement textures formed after the decompressional breakdown of omphacite, aiding in our understanding of the exhumation history of these lower-crustal continental basement rocks. ? Lamprophyre dikes in the northern field area were shown on the geologic map (Friderichsen and Surlyk, 1976) but have never been described or dated. The age of intrusion is particularly important for understanding their significance for the extensional evolution of East Greenland; based on what was previously known, these dikes could have intruded at any point between the Middle Devonian and the Eocene, a 300 million year gap of time. I used 40Ar/39Ar methods to separate and date phlogopite grains from the lamprophyres. The resulting 262 Ma and 264 Ma dates are interpreted to record the time of intrusion, which helps us to understand that the Permian was an important period of extension in East Greenland and now must be considered together with related Permian extension in Norway (i.e., Lofoten and the Oslo graben). Through the course of this research, it has become evident that further research needs to be conducted on rocks in Liverpool Land. First, granulite- and amphibolite- facies metamorphism was recognized to have variably retrograded the high-pressure assemblages in the eclogite pods but only amphibolite-facies assemblages were found within the country rocks that encapsulate them. Microprobe analyses and geothermobarometric information constraining the pressure and temperature conditions 64 for both the granulite- and amphibolite-facies portions of this retrograde path would be important to further understand their exhumation history. Secondly, additional geochronologic and thermochronologic studies are needed on rocks from the orthogneiss terrane to determine the timing of protolith emplacement and to further constrain the timing of the Caledonian migmatization and subsequent exhumation. Lastly, in this thesis, most of the field studies and laboratory analyses were focused on the Gubbedalen Shear Zone and the eclogite-containing footwall terrane. 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Evidence in North-East Greenland for late Silurian - early Devonian regional extension during the Caledonian orogeny: Geology, v.22, p. 916-916. Strachan, R.A., Nutman, A.P., and Friderichsen, J.D., 1995, SHRIMP U-Pb geochronology and metamorphic history of the Smallefjord sequence, NE Greenland Caledonides: Journal of the Geologic Society (London), vol. 152, p. 779-784. Wilson, M., Neuman, E.R., Davies, G.R., Timmerman, M.J., Heeremans, M., and Larsen, B.T., 2004, Permo-Carboniferous magmatism and rifting in Europe: introduction: Geological Society (London), Special Publications, vol. 223, p. 1-10 70 APPENDIX A STRUCTURAL DATA AND STATION LOCATIONS 71 Appendix A contains structural data obtained from metamorphic and mylonitic fabrics at specified stations. Station locations are given by latitude and longitude coordinates. The structural data are divided based on deformation history using the aforementioned nomenclature. The data are reported using azimuth directions and the right hand rule. 72 CP-2A Latitude N: 70? 35.522' Longitude W: 22? 14.114' Fabric Strike Dip Lineation Bearing Plunge S0 273 19 L0 174 13 S0 76 26 CP-3 Latitude N: 70? 36.046' Longitude W: 22? 14.530' Fabric Strike Dip Lineation Bearing Plunge C Plane 273 21 L0 8 37 S Plane 279 59 CP-4 Latitude N: 70? 36.089' Longitude W: 22? 15.229' Fabric Strike Dip Lineation Bearing Plunge S0 273 19 L0 3 18 CP-5 Latitude N: 70? 35.086' Longitude W: 22? 14.245' Fabric Strike Dip S0 218 38 CP-6 Latitude N: 70? 35.216' Longitude W: 22? 14.191' Fabric Strike Dip S0 223 40 CP-7 Latitude N: 70? 35.210' Longitude W: 22? 14.256' Fabric Strike Dip Lineation Bearing Plunge S1 203 30 L1 358 31 CP-9 Latitude N: 70? 35.078' Longitude W: 22? 14.001' Lineation Bearing Plunge L2 143 14 L2 358 29 L2 8 25 L2 12 21 73 CP-10 Latitude N: 70? 35.044' Longitude W: 22? 13.872' Fabric Strike Dip Lineation Bearing Plunge S2 23 24 L2 168 3 S2 310 12 L2 346 2 L2 158 24 L2 353 11 L2 348 4 L2 358 13 CP-11 Latitude N: 70? 34.978' Longitude W: 22? 13.767' Fabric Strike Dip Lineation Bearing Plunge S1 57 6 L1 175 11 S1 84 12 L1 186 11 L1 354 15 CP-13 Latitude N: 70? 34.929' Longitude W: 22? 13.567' Fabric Strike Dip S1 348 16 CP-14 Latitude N: 70? 34.781' Longitude W: 22? 13.460' Fabric Strike Dip Lineation Bearing Plunge S1 203 7 L1 354 2 CP-16 Latitude N: 70? 34.669' Longitude W: 22? 13.298' Fabric Strike Dip Lineation Bearing Plunge S2 343 15 L2 358 4 CP-18 Latitude N: 70? 34.778' Longitude W: 22? 14.165' Fabric Strike Dip Lineation Bearing Plunge C Plane 213 42 L2 38 4 S Plane 278 40 L2 30 15 S2 208 40 CP-20 Latitude N: 70? 34.583' Longitude W: 22? 14.295' Fabric Strike Dip Lineation Bearing Plunge S1 33 4 L1 3 0 74 CP-21 Latitude N: 70? 34.478' Longitude W: 22? 14.586' Fabric Strike Dip S0 353 75 CP-22 Latitude N: 70? 34.476' Longitude W: 22? 14.882' Fabric Strike Dip Lineation Bearing Plunge S1 346 37 L2 173 10 S1 355 54 S2 138 28 CP-23 Latitude N: 70? 34.471' Longitude W: 22? 15.012' Fabric Strike Dip S2 358 11 S2 313 15 S2 292 19 CP-24 Latitude N: 70? 34.336' Longitude W: 22? 14.624' Fabric Strike Dip Lineation Bearing Plunge S1 278 20 L1 3 23 CP-25 Latitude N: 70? 34.524' Longitude W: 22? 13.822' Fabric Strike Dip Lineation Bearing Plunge S2 248 20 L2 322 24 CP-27 Latitude N: 70? 35.455' Longitude W: 22? 13.200' Fabric Strike Dip Lineation Bearing Plunge S0 268 54 L0 310 43 CP-28 Latitude N: 70? 35.472' Longitude W: 22? 13.124' Fabric Strike Dip S0 263 56 CP-30 Latitude N: 70? 35.655' Longitude W: 22? 12.735' Fabric Strike Dip C Plane 232 56 S Plane 256 58 75 CP-31 Latitude N: 70? 35.644' Longitude W: 22? 12.763' Fabric Strike Dip S1 247 86 CP-32 Latitude N: 70? 35.664' Longitude W: 22? 12.734' Fabric Strike Dip S2 256 74 S2 274 51 CP-34 Fabric Strike Dip Lineation Bearing Plunge C Plane 243 68 L2 13 58 S Plane 278 59 CP-35 Latitude N: 70? 35.653' Longitude W: 22? 13.486' Lineation Bearing Plunge L2 3 43 L2 8 39 L2 350 39 CP-36 Latitude N: 70? 35.669' Longitude W: 22? 13.509' Fabric Strike Dip Lineation Bearing Plunge S1 253 63 L1 3 45 S2 264 38 L2 4 35 CP-40 Latitude N: 70? 34.022' Longitude W: 22? 11.621' Fabric Strike Dip Lineation Bearing Plunge S0 108 24 L0 18 25 CP-42 Latitude N: 70? 34.520' Longitude W: 22? 13.137' Fabric Strike Dip S0 100 10 CP-50 Latitude N: 70? 34.867' Longitude W: 22? 15.260' Fabric Strike Dip Lineation Bearing Plunge S1 280 10 L1 340 10 76 CP-56 Latitude N: 70? 34.888' Longitude W: 22? 16.321' Fabric Strike Dip Lineation Bearing Plunge S0 15 24 L0 202 5 S1 65 6 L1 4 4 CP-58 Latitude N: 70? 35.679' Longitude W: 22? 15.183' Fabric Strike Dip Lineation Bearing Plunge S1 192 30 L1 325 24 S1 208 45 L1 312 47 CP-60 Latitude N: 70? 35.864' Longitude W: 22? 16.333' Fabric Strike Dip Lineation Bearing Plunge S1 290 8 L1 352 7 S2 338 19 L2 190 10 CP-62 Latitude N: 70? 35.707' Longitude W: 22? 17.968' Fabric Strike Dip S0 325 90 CP-65 Latitude N: 70? 36.171' Longitude W: 22? 18.168' Fabric Strike Dip Lineation Bearing Plunge S0 245 52 L0 358 51 CP-66 Latitude N: 70? 36.463' Longitude W: 22? 18.190' Fabric Strike Dip S0 270 50 CP-67 Latitude N: 70? 36.455' Longitude W: 22? 17.954' Fabric Strike Dip Lineation Bearing Plunge S2 270 40 L2 1 39 77 CP-70 Latitude N: 70? 35.779' Longitude W: 22? 13.477' Fabric Strike Dip Lineation Bearing Plunge S2 271 24 L2 2 5 L2 10 24 L2 9 32 L2 2 25 L2 358 15 L2 1 26 L2 4 11 L2 4 30 CP-71 Latitude N: 70? 35.892' Longitude W: 22? 13.357' Fabric Strike Dip Lineation Bearing Plunge S2 273 38 L2 6 39 CP-72 Latitude N: 70? 35.892' Longitude W: 22? 13.357' Fabric Strike Dip Lineation Bearing Plunge S2 278 31 L2 2 31 CP-73 Latitude N: 70? 36.039' Longitude W: 22? 12.995' Fabric Strike Dip Lineation Bearing Plunge S2 274 26 L2 4 27 S2 280 22 L2 14 10 S2 280 24 L2 9 25 CP-74 Latitude N: 70? 36.217' Longitude W: 22? 13.095' Fabric Strike Dip Lineation Bearing Plunge S2 279 41 L2 6 33 S2 272 15 L2 12 12 CP-75 Latitude N: 70? 36.255' Longitude W: 22? 13.267' Fabric Strike Dip Lineation Bearing Plunge S2 250 29 L2 5 30 78 CP-76 Latitude N: 70? 36.271' Longitude W: 22? 13.196' Fabric Strike Dip C Plane 250 35 S Plane 250 51 CP-77 Latitude N: 70? 36.317' Longitude W: 22? 13.207' Fabric Strike Dip Lineation Bearing Plunge S2 280 25 L2 6 28 CP-78 Latitude N: 70? 36.290' Longitude W: 22? 16.493' Fabric Strike Dip Lineation Bearing Plunge S2 283 42 L2 2 44 L2 356 6 CP-83 Latitude N: 70? 36.323' Longitude W: 22? 15.390' Fabric Strike Dip Lineation Bearing Plunge S2 260 44 L2 34 24 CP-84 Latitude N: 70? 35.106' Longitude W: 22? 14.058' S2 L2 Strike Dip Bearing Plunge 84.1 58 11 84.1 138 15 84.2 85 12 84.2 139 15 84.3 45 16 84.3 140 19 84.4 82 18 84.4 146 15 84.5 40 17 84.5 154 17 84.6 8 30 84.6 120 24 84.7 344 34 84.7 148 9 84.8 5 20 84.8 144 19 84.9 16 15 84.9 136 14 84.10 340 34 84.10 141 11 84.11 342 14 84.11 140 4 84.12 310 25 84.12 338 8 84.13 270 17 84.13 323 14 84.14 200 30 84.14 312 17 84.15 196 6 84.15 314 5 79 CP-85 Latitude N: 70? 34.875' Longitude W: 22? 13.943' Fabric Strike Dip Fabric Bearing Plunge S2 243 7 L2 8 35 L2 357 20 L2 355 22 L2 2 37 L2 0 44 L2 4 38 L2 340 4 CP-87 Latitude N: 70? 34.976' Longitude W: 22? 12.567' Fabric Strike Dip Fabric Bearing Plunge S2 140 17 L2 170 11 CP-88 Latitude N: 70? 35.190' Longitude W: 22? 11.210' Fabric Strike Dip Fabric Bearing Plunge S2 52 41 L2 168 44 CP-89 Latitude N: 70? 35.296' Longitude W: 22? 10.385' Fabric Strike Dip Fabric Bearing Plunge S2 130 18 L2 155 4 M-10 Latitude N: 70? 51.573' Longitude W: 22? 19.459' Fabric Strike Dip S1 126 31 M-11 Latitude N: 70? 52.378' Longitude W: 22? 19.255' Fabric Strike Dip S1 150 82 80 APPENDIX B MINERAL CHEMISTRY DATA FROM MICROPROBE ANALYSIS 81 PART I Appendix B, Part I contains mineral chemical data obtained from microprobe analysis performed at the Institute of Geosciences, University of Oslo, Norway, under the supervision of Dr. Muriel Erambert. The data were collected on the 29th, 30th, and 31st of May 2007. Pyroxene, garnet, plagioclase, and amphibole were analyzed from three eclogite samples, CP-47, CP-52A, and CP-92, which represented a spectrum of retrogression. The following tables are grouped by sample number and mineral type. The number at the top of the column corresponds to the order of the analyses done in a particular day. Quantitative analyses were performed in Wavelength-Dispersive System (WDS) mode on a Cameca Sx100 electron microprobe. Analytical conditions were: accelerating voltage 15 kV, current 15 nA, and counting time 10 s on peak (and 5 s on each background position). Na and K were analyzed first. Calibration standards were wollastonite (Ca and Si), MgO (Mg), Al2O3 (Al), Fe metal, pyrophanite (Mn and Ti), Cr2O3 (Cr), orthoclase (K), albite and omphacite. For pyroxene, garnet, and amphibole analyses, a focused electron beam was used, but when analyzing feldspars a defocalized electron beam with a diameter of 10 micrometers was used, due to the sensitivity of feldspar to the electron beam. Qualitative Energy-Dispersive System (EDS) analysis was used to quickly identify minerals prior to WDS analysis. The Cameca Sx100 is fitted with an EDS system from Princeton Gamma Tech. 82 MICROPROBE ANALYSES OF PYROXENE FROM ECLOGITE SAMPLE CP-47 #1 #7 #8 #11 #14 #15 #24 #26 #31 #32 #33 #39 #43 #45 Weight % oxide SiO2 51.268 49.229 49.993 49.858 50.141 50.553 51.379 50.472 50.791 49.858 50.799 50.699 50.455 51.052 TiO2 0.244 0.344 0.367 0.432 0.375 0.305 0.255 0.289 0.227 0.240 0.235 0.259 0.275 0.217 Al2O3 2.632 4.903 4.894 4.988 4.244 3.866 2.949 4.542 3.376 4.036 4.147 3.412 4.040 2.910 Cr2O3 0.009 0.038 0.000 0.000 0.016 0.022 0.058 0.000 0.016 0.018 0.000 0.016 0.003 0.025 FeO 10.895 10.364 10.127 9.198 9.914 9.283 9.717 13.903 10.534 10.917 9.950 9.975 9.710 9.928 MnO 0.142 0.147 0.121 0.111 0.099 0.044 0.085 0.118 0.068 0.165 0.116 0.142 0.103 0.068 MgO 12.875 12.069 12.043 12.339 12.094 12.475 12.625 12.563 11.961 12.036 11.931 12.452 12.006 12.396 CaO 21.284 21.634 21.174 21.924 22.222 21.960 22.462 17.953 22.378 20.713 21.538 22.078 22.388 22.294 Na2O 0.446 0.667 0.621 0.489 0.551 0.623 0.739 0.613 0.821 0.710 0.790 0.474 0.642 0.373 K2O 0.000 0.011 0.019 0.039 0.007 0.005 0.000 0.006 0.025 0.002 0.001 0.000 0.006 0.000 Total 99.799 99.411 99.363 99.383 99.667 99.142 100.274 100.463 100.203 98.700 99.512 99.512 99.633 99.268 Atoms per formula unit (4 cations, 6 oxygens) Si 1.923 1.847 1.878 1.869 1.879 1.898 1.909 1.888 1.894 1.888 1.905 1.903 1.890 1.924 Ti 0.007 0.010 0.010 0.012 0.011 0.009 0.007 0.008 0.006 0.007 0.007 0.007 0.008 0.006 Al 0.116 0.217 0.217 0.220 0.187 0.171 0.129 0.200 0.148 0.180 0.183 0.151 0.178 0.129 Cr 0.001 0.003 0.000 0.000 0.001 0.002 0.004 0.000 0.001 0.001 0.000 0.001 0.000 0.002 Fe3+ 0.056 0.116 0.052 0.056 0.073 0.059 0.088 0.052 0.110 0.080 0.051 0.061 0.072 0.036 Fe2+ 0.285 0.209 0.266 0.233 0.238 0.233 0.214 0.383 0.218 0.265 0.261 0.252 0.232 0.277 Mn 0.005 0.005 0.004 0.004 0.003 0.001 0.003 0.004 0.002 0.005 0.004 0.005 0.003 0.002 Mg 0.720 0.675 0.674 0.689 0.676 0.698 0.699 0.701 0.665 0.680 0.667 0.697 0.671 0.696 Ca 0.855 0.870 0.852 0.880 0.892 0.883 0.894 0.720 0.894 0.840 0.865 0.888 0.899 0.900 Na 0.032 0.049 0.045 0.036 0.040 0.045 0.053 0.044 0.059 0.052 0.057 0.035 0.047 0.027 K 0.000 0.001 0.001 0.002 0.000 0.000 0.000 0.000 0.001 0.000 0.000 0.000 0.000 0.000 Sum 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 83 MICROPROBE ANALYSES OF GARNET FROM ECLOGITE SAMPLE CP-47 #3 #4 #5 #17 #18 #28 #35 #36 #47 #48 Weight % oxide SiO2 38.879 38.794 39.046 39.416 39.247 39.423 39.172 39.147 39.624 39.446 TiO2 0.058 0.078 0.067 0.063 0.038 0.053 0.068 0.073 0.085 0.063 Al2O3 22.108 22.337 22.205 22.250 22.084 22.008 22.271 22.494 22.014 21.966 Cr2O3 0.000 0.028 0.000 0.026 0.000 0.028 0.000 0.018 0.000 0.000 FeO 20.272 18.750 18.879 18.835 22.226 19.728 19.277 18.959 19.556 19.292 MnO 0.281 0.298 0.296 0.328 0.456 0.322 0.287 0.243 0.307 0.210 MgO 7.039 7.635 7.725 7.655 7.491 7.695 7.760 7.790 7.664 7.541 CaO 11.046 11.448 11.200 11.617 9.188 10.957 11.470 11.819 11.556 11.441 Na2O 0.020 0.000 0.000 0.000 0.042 0.000 0.000 0.000 0.129 0.047 K2O 0.000 0.007 0.004 0.005 0.000 0.011 0.019 0.010 0.001 0.000 Total 99.709 99.380 99.425 100.201 100.777 100.228 100.329 100.555 100.939 100.012 Atoms per formula unit (4 cations, 6 oxygens) Si 2.975 2.961 2.980 2.985 2.980 2.991 2.964 2.952 2.982 2.997 Ti 0.003 0.004 0.004 0.004 0.002 0.003 0.004 0.004 0.005 0.004 Al 1.994 2.009 1.997 1.986 1.976 1.968 1.986 1.999 1.952 1.967 Cr 0.000 0.004 0.000 0.004 0.000 0.004 0.000 0.003 0.000 0.000 Fe3+ 0.051 0.057 0.036 0.033 0.066 0.041 0.079 0.087 0.093 0.038 Fe2+ 1.246 1.140 1.169 1.160 1.345 1.210 1.141 1.108 1.138 1.188 Mn 0.018 0.019 0.019 0.021 0.029 0.021 0.018 0.016 0.020 0.014 Mg 0.803 0.869 0.879 0.864 0.848 0.870 0.875 0.876 0.860 0.854 Ca 0.906 0.936 0.916 0.943 0.747 0.891 0.930 0.955 0.932 0.931 Na 0.003 0.000 0.000 0.000 0.006 0.000 0.000 0.000 0.019 0.007 K 0.000 0.001 0.000 0.000 0.000 0.001 0.002 0.001 0.000 0.000 Sum 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 84 MICROPROBE ANALYSES OF PLAGIOCLASE FROM ECLOGITE SAMPLE CP-47 #2 #6 #9 #10 #16 #19 #20 #21 #23 #27 #30 #34 #37 #40 #42 #44 #46 Weight % oxide SiO2 60.413 60.078 59.900 60.779 60.625 60.512 55.611 59.964 62.063 61.312 59.968 60.655 58.535 59.117 58.229 59.954 59.194 TiO2 0.000 0.003 0.000 0.003 0.000 0.012 0.025 0.000 0.003 0.000 0.000 0.010 0.000 0.000 0.000 0.000 0.000 Al2O3 24.723 25.027 25.384 24.761 24.751 24.508 27.860 24.973 23.992 24.523 25.046 24.408 26.101 25.827 26.441 25.156 25.492 Cr2O3 0.000 0.018 0.003 0.000 0.000 0.000 0.028 0.000 0.000 0.000 0.009 0.000 0.029 0.000 0.000 0.000 0.004 FeO 0.234 0.238 0.233 0.169 0.197 0.162 0.219 0.160 0.151 0.144 0.217 0.215 0.311 0.244 0.219 0.198 0.259 MnO 0.022 0.050 0.001 0.009 0.030 0.040 0.000 0.036 0.012 0.021 0.000 0.017 0.012 0.000 0.000 0.000 0.000 MgO 0.000 0.000 0.018 0.000 0.000 0.000 0.000 0.000 0.010 0.000 0.000 0.008 0.000 0.000 0.000 0.000 0.018 CaO 6.908 7.113 7.291 6.505 6.794 6.701 10.642 7.056 5.773 6.044 7.221 6.566 8.548 7.922 8.464 7.357 7.568 Na2O 7.633 7.666 7.695 7.926 7.778 7.784 5.799 7.636 8.264 8.016 7.380 7.798 6.778 7.084 6.624 7.450 7.186 K2O 0.196 0.178 0.169 0.205 0.242 0.223 0.116 0.219 0.271 0.266 0.275 0.359 0.220 0.257 0.202 0.285 0.279 Total 100.135 100.375 100.699 100.361 100.420 99.945 100.303 100.047 100.543 100.331 100.121 100.040 100.537 100.453 100.181 100.404 100.005 Atoms per formula unit (5 cations, 8 oxygens) Si 2.690 2.672 2.658 2.697 2.692 2.698 2.501 2.675 2.742 2.717 2.673 2.703 2.610 2.633 2.602 2.667 2.646 Ti 0.000 0.000 0.000 0.000 0.000 0.000 0.001 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 Al 1.297 1.312 1.327 1.295 1.295 1.288 1.477 1.313 1.249 1.281 1.316 1.282 1.371 1.356 1.393 1.319 1.343 Cr 0.000 0.002 0.000 0.000 0.000 0.000 0.002 0.000 0.000 0.000 0.001 0.000 0.003 0.000 0.000 0.000 0.000 Fe 0.009 0.009 0.009 0.006 0.007 0.006 0.008 0.006 0.006 0.005 0.008 0.008 0.012 0.009 0.008 0.007 0.010 Mn 0.001 0.002 0.000 0.000 0.001 0.002 0.000 0.001 0.000 0.001 0.000 0.001 0.000 0.000 0.000 0.000 0.000 Mg 0.000 0.000 0.001 0.000 0.000 0.000 0.000 0.000 0.001 0.000 0.000 0.001 0.000 0.000 0.000 0.000 0.001 Ca 0.330 0.339 0.347 0.309 0.323 0.320 0.513 0.337 0.273 0.287 0.345 0.314 0.408 0.378 0.405 0.351 0.362 Na 0.659 0.661 0.662 0.682 0.670 0.673 0.506 0.660 0.708 0.689 0.638 0.674 0.586 0.612 0.574 0.643 0.623 K 0.011 0.010 0.010 0.012 0.014 0.013 0.007 0.012 0.015 0.015 0.016 0.020 0.013 0.015 0.012 0.016 0.016 Sum 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 85 MICROPROBE ANALYSES OF AMPHIBOLE FROM ECLOGITE SAMPLES 47-#12 47-#13 47-#22 47-#38 47-#41 52A-#2 92-#65 92-#72 92-#73 92-#74 92-#80 Weight % oxide SiO2 43.472 43.913 43.674 44.166 43.351 41.297 41.541 41.010 40.972 40.974 41.990 TiO2 1.551 1.691 1.473 0.839 1.368 0.509 1.276 2.173 0.961 0.761 1.480 Al2O3 11.431 11.871 11.295 10.843 11.826 15.473 13.670 14.203 15.374 14.925 13.441 Cr2O3 0.000 0.000 0.013 0.041 0.019 0.000 0.022 0.000 0.000 0.037 0.009 FeO 13.952 12.860 14.039 14.625 14.850 11.765 14.371 12.947 13.385 13.526 14.028 MnO 0.075 0.061 0.049 0.070 0.052 0.058 0.102 0.075 0.089 0.121 0.053 MgO 12.295 12.560 12.283 12.074 11.867 13.233 12.028 12.031 12.238 12.611 12.129 CaO 11.668 11.525 11.384 11.799 11.661 11.095 11.048 11.399 11.261 11.465 11.378 Na2O 1.738 1.868 1.763 1.464 1.588 2.654 3.205 3.059 3.191 3.170 3.033 K2O 0.428 0.473 0.512 0.635 0.673 0.902 0.027 0.027 0.022 0.025 0.017 Total 96.614 96.826 96.488 96.559 97.258 96.991 97.293 96.929 97.497 97.619 97.562 Atoms per formula unit (16 cations, 22 oxygens) Si 6.492 6.502 6.527 6.612 6.460 6.114 6.195 6.108 6.070 6.073 6.231 Ti 0.174 0.188 0.166 0.094 0.153 0.057 0.143 0.243 0.107 0.085 0.165 Al 2.012 2.071 1.989 1.913 2.077 2.700 2.403 2.493 2.684 2.607 2.351 Cr 0.000 0.000 0.004 0.012 0.005 0.000 0.006 0.000 0.000 0.011 0.003 Fe 1.742 1.592 1.754 1.831 1.851 1.456 1.792 1.613 1.658 1.676 1.741 Mn 0.009 0.008 0.006 0.009 0.007 0.007 0.013 0.009 0.011 0.015 0.007 Mg 2.738 2.772 2.737 2.695 2.637 2.921 2.674 2.672 2.703 2.787 2.683 Ca 1.867 1.828 1.823 1.892 1.862 1.760 1.765 1.819 1.787 1.821 1.809 Na 0.503 0.536 0.511 0.425 0.459 0.762 0.927 0.883 0.916 0.911 0.873 K 0.082 0.089 0.098 0.121 0.128 0.170 0.005 0.005 0.004 0.005 0.003 Sum 15.620 15.587 15.615 15.604 15.638 15.946 15.923 15.846 15.941 15.991 15.865 86 MICROPROBE ANALYSES OF PYROXENE FROM ECLOGITE SAMPLE CP-52A #1 #3 #8 #10 #11 #12 #13 #16 #18 #20 #22 Weight % oxide SiO2 54.864 50.314 53.696 53.876 54.055 53.007 53.557 54.719 54.239 54.109 54.650 TiO2 0.187 0.255 0.285 0.354 0.420 0.402 0.374 0.202 0.209 0.165 0.207 Al2O3 12.196 9.309 12.551 13.026 13.007 13.266 13.118 12.334 12.661 12.022 12.406 Cr2O3 0.009 0.020 0.029 0.000 0.029 0.000 0.000 0.003 0.000 0.013 0.013 FeO 4.463 7.408 4.643 4.369 4.476 5.434 4.380 4.375 4.383 4.482 4.536 MnO 0.026 0.072 0.009 0.000 0.026 0.025 0.000 0.035 0.000 0.077 0.034 MgO 8.138 10.575 8.420 8.018 8.204 8.592 8.048 8.085 8.015 8.262 8.156 CaO 14.392 18.857 15.240 14.554 14.620 15.739 14.858 14.360 14.234 14.621 14.423 Na2O 6.246 2.655 5.587 5.909 5.878 5.103 5.819 6.184 6.248 6.013 6.046 K2O 0.002 0.000 0.000 0.000 0.000 0.000 0.002 0.000 0.027 0.001 0.010 Total 100.528 99.470 100.466 100.110 100.720 101.573 100.162 100.302 100.020 99.771 100.484 Atoms per formula unit (4 cations, 6 oxygens) Si 1.946 1.849 1.912 1.921 1.917 1.875 1.910 1.945 1.931 1.935 1.941 Ti 0.005 0.007 0.008 0.009 0.011 0.011 0.010 0.005 0.006 0.004 0.006 Al 0.510 0.403 0.527 0.547 0.544 0.553 0.551 0.517 0.531 0.507 0.519 Cr 0.000 0.001 0.001 0.000 0.001 0.000 0.000 0.000 0.000 0.000 0.000 Fe3+ 0.019 0.074 0.019 0.000 0.003 0.025 0.011 0.008 0.027 0.031 0.003 Fe2+ 0.114 0.154 0.120 0.130 0.130 0.136 0.120 0.122 0.103 0.103 0.131 Mn 0.001 0.002 0.000 0.000 0.001 0.001 0.000 0.001 0.000 0.002 0.001 Mg 0.430 0.579 0.447 0.426 0.434 0.453 0.428 0.428 0.426 0.440 0.432 Ca 0.547 0.742 0.581 0.556 0.556 0.596 0.568 0.547 0.543 0.560 0.549 Na 0.429 0.189 0.386 0.409 0.404 0.350 0.402 0.426 0.431 0.417 0.416 K 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.001 0.000 0.000 Sum 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 87 MICROPROBE ANALYSES OF GARNET FROM ECLOGITE SAMPLE CP-52A #5 #6 #9 #14 #15 #17 #19 #21 #23 Weight % oxide SiO2 39.335 39.292 39.632 39.819 39.757 39.553 39.707 39.555 38.757 TiO2 0.083 0.083 0.075 0.085 0.080 0.070 0.107 0.098 0.062 Al2O3 22.373 22.348 22.237 22.469 22.180 22.443 22.322 22.235 22.036 Cr2O3 0.000 0.018 0.000 0.001 0.000 0.004 0.006 0.013 0.000 FeO 18.546 18.848 18.305 19.053 18.628 18.537 18.849 18.485 18.299 MnO 0.178 0.200 0.241 0.142 0.199 0.195 0.214 0.257 0.221 MgO 7.763 7.783 7.622 7.581 7.732 7.811 7.780 7.858 7.906 CaO 12.138 11.785 12.358 11.557 12.047 11.984 11.963 12.078 11.887 Na2O 0.000 0.036 0.000 0.066 0.004 0.000 0.000 0.000 0.003 K2O 0.000 0.000 0.000 0.000 0.000 0.011 0.000 0.006 0.000 Total 100.420 100.398 100.475 100.777 100.630 100.612 100.952 100.589 99.175 Atoms per formula unit (8 cations, 12 oxygens) Si 2.969 2.967 2.991 2.999 2.997 2.979 2.984 2.980 2.959 Ti 0.005 0.005 0.004 0.005 0.005 0.004 0.006 0.006 0.004 Al 1.990 1.989 1.978 1.994 1.970 1.992 1.977 1.974 1.983 Cr 0.000 0.001 0.000 0.000 0.000 0.000 0.000 0.001 0.000 Fe3+ 0.063 0.071 0.032 0.008 0.028 0.043 0.043 0.054 0.093 Fe2+ 1.107 1.119 1.123 1.192 1.146 1.124 1.142 1.111 1.075 Mn 0.011 0.013 0.015 0.009 0.013 0.012 0.014 0.016 0.014 Mg 0.873 0.876 0.858 0.851 0.869 0.877 0.872 0.883 0.900 Ca 0.981 0.953 0.999 0.932 0.973 0.967 0.963 0.975 0.972 Na 0.000 0.005 0.000 0.010 0.001 0.000 0.000 0.000 0.000 K 0.000 0.000 0.000 0.000 0.000 0.001 0.000 0.001 0.000 Sum 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 88 MICROPROBE ANALYSES OF PYROXENE FROM ECLOGITE SAMPLE CP-92 #49 #53 #55 #58 #59 #63 #64 #66 #67 #76 #77 #79 Weight % oxide SiO2 49.897 49.845 52.798 52.526 51.463 48.748 48.955 50.594 49.456 49.148 50.402 49.242 TiO2 0.249 0.227 0.097 0.137 0.330 0.585 0.599 0.207 0.564 0.237 0.188 0.295 Al2O3 10.182 9.991 1.349 1.959 3.116 6.309 6.876 10.991 8.026 6.694 10.868 8.057 Cr2O3 0.013 0.000 0.039 0.013 0.000 0.012 0.038 0.000 0.004 0.022 0.000 0.031 FeO 12.084 10.658 12.367 12.695 8.861 9.794 9.872 10.004 9.286 9.088 10.383 11.231 MnO 0.142 0.094 0.136 0.152 0.123 0.089 0.134 0.085 0.090 0.124 0.116 0.137 MgO 8.486 8.464 11.721 11.288 12.998 12.149 10.958 8.363 10.792 11.948 8.433 11.613 CaO 15.100 17.180 20.119 20.246 21.743 20.732 20.972 15.886 20.543 21.487 16.596 19.439 Na2O 3.511 3.092 1.330 1.558 0.702 0.876 1.216 3.606 1.782 0.980 3.561 1.050 K2O 0.002 0.000 0.000 0.000 0.000 0.005 0.006 0.000 0.000 0.000 0.000 0.000 Total 99.671 99.557 99.959 100.580 99.340 99.302 99.631 99.740 100.547 99.733 100.551 101.099 Atoms per formula unit (4 cations, 6 oxygens) Si 1.849 1.850 1.981 1.959 1.925 1.823 1.828 1.863 1.819 1.825 1.843 1.812 Ti 0.007 0.006 0.003 0.004 0.009 0.016 0.017 0.006 0.016 0.007 0.005 0.008 Al 0.445 0.437 0.060 0.086 0.137 0.278 0.303 0.477 0.348 0.293 0.468 0.349 Cr 0.001 0.000 0.003 0.001 0.000 0.001 0.003 0.000 0.000 0.002 0.000 0.002 Fe3+ 0.096 0.074 0.066 0.100 0.045 0.105 0.093 0.043 0.109 0.112 0.088 0.083 Fe2+ 0.278 0.257 0.322 0.296 0.232 0.201 0.215 0.265 0.176 0.170 0.230 0.263 Mn 0.004 0.003 0.004 0.005 0.004 0.003 0.004 0.003 0.003 0.004 0.004 0.004 Mg 0.469 0.468 0.656 0.628 0.725 0.677 0.610 0.459 0.592 0.662 0.460 0.637 Ca 0.599 0.683 0.809 0.809 0.871 0.831 0.839 0.627 0.810 0.855 0.650 0.766 Na 0.252 0.222 0.097 0.113 0.051 0.064 0.088 0.257 0.127 0.071 0.252 0.075 K 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 Sum 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 89 MICROPROBE ANALYSES OF GARNET FROM ECLOGITE SAMPLE CP-92 #52 #61 #68 #69 #78 Weight % oxide SiO2 39.102 39.046 39.196 38.978 38.937 TiO2 0.057 0.098 0.065 0.072 0.077 Al2O3 22.004 21.872 21.844 21.666 21.723 Cr2O3 0.019 0.000 0.004 0.010 0.000 FeO 22.263 21.932 21.964 22.601 22.405 MnO 0.356 0.328 0.342 0.421 0.356 MgO 6.561 6.528 6.579 7.093 6.417 CaO 10.368 10.797 10.435 9.478 10.375 Na2O 0.000 0.018 0.137 0.000 0.085 K2O 0.000 0.001 0.004 0.000 0.016 Total 100.734 100.625 100.575 100.323 100.395 Atoms per formula unit (8 cations, 12 oxygens) Si 2.981 2.979 2.989 2.982 2.981 Ti 0.003 0.006 0.004 0.004 0.004 Al 1.977 1.967 1.963 1.953 1.960 Cr 0.003 0.000 0.001 0.001 0.000 Fe3+ 0.050 0.066 0.072 0.073 0.042 Fe2+ 1.369 1.333 1.329 1.373 1.392 Mn 0.023 0.021 0.022 0.027 0.023 Mg 0.746 0.743 0.748 0.809 0.732 Ca 0.847 0.883 0.852 0.777 0.851 Na 0.000 0.003 0.020 0.000 0.013 K 0.000 0.000 0.000 0.000 0.002 Sum 8.000 8.000 8.000 8.000 8.000 90 MICROPROBE ANALYSES OF PLAGIOCLASE FROM ECLOGITE SAMPLES CP-47 AND CP-52A #50 #51 #54 #56 #57 #60 #62 #70 #71 #75 CP-52A-#4 Weight % oxide SiO2 63.986 63.751 64.480 66.904 65.997 62.675 63.511 60.103 61.282 62.061 68.556 TiO2 0.000 0.000 0.012 0.000 0.008 0.007 0.003 0.010 0.005 0.000 0.010 Al2O3 22.964 22.452 22.469 21.039 21.356 23.631 22.975 25.689 24.438 23.931 19.881 Cr2O3 0.029 0.016 0.000 0.028 0.000 0.000 0.012 0.028 0.007 0.016 0.000 FeO 0.232 0.216 0.248 0.250 0.243 0.135 0.161 0.208 0.257 0.399 0.108 MnO 0.054 0.000 0.000 0.004 0.000 0.021 0.022 0.009 0.000 0.030 0.070 MgO 0.002 0.012 0.000 0.013 0.000 0.000 0.015 0.000 0.000 0.000 0.000 CaO 4.403 3.918 3.639 1.914 2.352 5.177 4.350 7.224 6.102 5.332 0.319 Na2O 9.467 9.312 9.779 10.828 10.568 8.864 9.283 7.725 8.113 8.828 11.563 K2O 0.000 0.008 0.001 0.005 0.005 0.018 0.010 0.005 0.022 0.000 0.060 Total 101.140 99.688 100.633 100.987 100.533 100.531 100.347 101.005 100.230 100.601 100.570 Atoms per formula unit (5 cations, 8 oxygens) Si 2.800 2.823 2.830 2.911 2.889 2.764 2.799 2.655 2.717 2.741 2.981 Ti 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 Al 1.184 1.172 1.162 1.079 1.102 1.228 1.193 1.337 1.277 1.246 1.019 Cr 0.002 0.001 0.000 0.002 0.000 0.000 0.001 0.002 0.001 0.001 0.000 Fe 0.008 0.008 0.009 0.009 0.009 0.005 0.006 0.008 0.010 0.015 0.004 Mn 0.002 0.000 0.000 0.000 0.000 0.001 0.001 0.000 0.000 0.001 0.003 Mg 0.000 0.001 0.000 0.001 0.000 0.000 0.001 0.000 0.000 0.000 0.000 Ca 0.206 0.186 0.171 0.089 0.110 0.245 0.205 0.342 0.290 0.252 0.015 Na 0.803 0.799 0.832 0.913 0.897 0.758 0.793 0.661 0.697 0.756 0.975 K 0.000 0.000 0.000 0.000 0.000 0.001 0.001 0.000 0.001 0.000 0.003 Sum 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 5.000 91 PART II Appendix B, Part II contains mineral chemical data obtained from microprobe analysis performed at the University of Kentucky, in Lexington, Kentucky, under the direction of Dr. David Moecher. The data were collected on the 17th, 18th, and 19th of December 2007. Pyroxene, garnet, plagioclase, and amphibole were analyzed from three eclogite samples, CP-47, CP-52A, and CP-92, which represented a spectrum of retrogression. The following tables are grouped by sample number and mineral type. Each data column represents the average of two spot analyses taken a few microns apart. Mineral compositions were determined using the ARL-SEMQ microprobe at the university if Kentucky. Most minerals were analyzed in point mode, using WDS at 15kV and 15 nA, except for plagioclase, which was analyzed using a rastered beam (10 X 10 ?m) at 15kV and 10 nA to minimize loss of Na and K. Typical count times were 10-20 s on peak, and 5-10 s for background counts. Natural USNM standards were used, ZAF corrections were made using Probewin v, 5.32 (after Anderson and Moecher 2007). 92 ANALYSES OF GARNETS FROM ECLOGITES CP-52A, CP-92 52A-C1 52A-C2 52A-C3 92-C1 92-C2 92-C3 Weight % oxide SiO2 39.748 39.692 40.004 39.479 39.360 39.104 TiO2 0.064 0.091 0.083 0.085 0.076 0.071 Al2O3 22.979 23.173 22.864 22.368 22.593 22.007 FeO 18.101 18.004 18.190 21.460 21.770 21.394 MnO 0.253 0.299 0.275 0.345 0.375 0.358 MgO 7.673 8.023 7.822 6.851 6.751 6.613 CaO 11.703 11.479 11.515 9.929 9.998 10.206 Na2O 0.000 0.034 0.070 0.026 0.003 0.032 K2O 0.000 0.000 0.000 0.000 0.000 0.000 Total 100.521 100.795 100.823 100.543 100.925 99.786 Atoms per formula unit (8 cations, 12 oxygens) Si 2.994 2.976 3.002 3.007 2.989 3.004 Ti 0.004 0.005 0.005 0.005 0.004 0.004 Al 2.040 2.048 2.022 2.008 2.022 1.992 Fe 3+ 0.000 0.000 0.000 0.000 0.000 0.000 Fe 2+ 1.140 1.129 1.142 1.367 1.382 1.374 Mn 0.016 0.019 0.017 0.022 0.024 0.023 Mg 0.862 0.897 0.875 0.778 0.764 0.757 Ca 0.944 0.922 0.926 0.810 0.813 0.840 Na 0.000 0.005 0.010 0.004 0.000 0.005 K 0.000 0.000 0.000 0.000 0.000 0.000 Sum 8.000 8.000 8.000 8.000 8.000 8.000 93 ANALYSES OF PYROXENE FROM ECLOGITE SAMPLE CP-52A Omp 2 C Omp 2 R1 Omp 2 R2 Omp 1 C Omp 3C Weight % oxide SiO2 54.095 49.793 49.255 54.289 54.458 TiO2 0.171 0.195 0.189 0.154 0.170 Al2O3 12.951 8.491 9.864 12.872 13.183 FeO 4.222 7.884 7.670 4.239 4.741 MnO 0.007 0.045 0.056 0.031 0.035 MgO 9.336 12.742 11.785 9.409 9.560 CaO 13.941 19.671 19.004 13.841 14.487 Na2O 5.495 1.791 2.033 5.746 5.617 K2O 0.000 0.000 0.000 0.000 0.000 Total 100.220 100.612 99.858 100.582 102.252 Atoms per formula unit (4 cations, 8 oxygens) Si 1.923 1.809 1.802 1.919 1.898 Ti 0.005 0.005 0.005 0.004 0.004 Al 0.543 0.364 0.424 0.536 0.541 Fe 3+ 0.000 0.135 0.106 0.011 0.034 Fe 2+ 0.126 0.105 0.129 0.115 0.105 Mn 0.000 0.001 0.002 0.001 0.001 Mg 0.495 0.690 0.644 0.496 0.497 Ca 0.531 0.766 0.746 0.524 0.541 Na 0.379 0.126 0.144 0.394 0.380 K 0.000 0.000 0.000 0.000 0.000 Sum 4.000 4.000 4.000 4.000 4.000 94 ANALYSES OF AMPHIBOLE FROM ECLOGITE SAMPLE CP-47 G2 - AMP1 G2 - AMP2 CPX 1 - AMP1 CPX 1 - AMP2 CPX 1 - AMP3 Weight % oxide SiO2 42.826 42.766 44.563 44.333 44.297 TiO2 0.631 0.632 1.298 2.421 0.906 Al2O3 14.467 14.086 11.686 11.524 12.291 FeO 13.891 14.008 13.992 11.491 13.484 MnO 0.072 0.072 0.096 0.051 0.066 MgO 12.863 12.513 12.764 13.673 13.054 CaO 11.088 11.216 11.273 12.015 11.566 Na2O 2.249 1.928 1.910 1.893 1.928 K2O 0.435 0.413 0.222 0.277 0.171 Total 98.522 97.633 97.804 97.678 97.762 Atoms per formula unit (16 cations, 23 oxygens) Si 6.259 6.307 6.544 6.470 6.496 Ti 0.069 0.070 0.143 0.266 0.100 Al 2.492 2.448 2.023 1.982 2.124 Fe 1.698 1.728 1.718 1.403 1.654 Mn 0.009 0.009 0.012 0.006 0.008 Mg 2.803 2.751 2.794 2.975 2.854 Ca 1.736 1.772 1.774 1.879 1.817 Na 0.637 0.551 0.544 0.536 0.548 K 0.081 0.078 0.042 0.052 0.032 Sum 15.785 15.714 15.594 15.567 15.633 95 MICROPROBE ANALYSES OF PYROXENE FROM ECLOGITE SAMPLE CP-47 CPX - G2 CPX - G3 CPX1 - 1 CPX1 - 2 CPX1 - 3 CPX1 - 4 CPX1 - 5 CPX1 - 6 CPX2 - 1 CPX2 - 2 CPX2 - 3 Weight % oxide SiO2 51.603 52.477 49.129 48.872 49.273 48.779 51.410 50.938 51.613 50.572 48.942 TiO2 0.273 0.171 0.424 0.412 0.510 0.425 0.294 0.249 0.181 0.261 0.353 Al2O3 12.809 12.988 5.145 5.971 5.092 6.092 3.447 4.074 3.082 3.481 7.907 FeO 5.340 5.211 9.529 9.685 9.748 9.766 8.680 9.182 8.845 8.975 9.892 MnO 0.026 0.021 0.070 0.107 0.107 0.068 0.041 0.092 0.104 0.070 0.083 MgO 10.014 9.462 12.850 12.914 13.658 12.958 14.001 13.219 14.084 13.312 12.484 CaO 17.136 16.220 21.106 21.177 21.600 21.063 21.269 21.373 22.016 21.842 18.315 Na2O 4.246 4.890 0.911 0.637 0.733 0.719 0.833 0.776 0.524 0.646 1.208 K2O 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 Total 101.448 101.440 99.164 99.775 100.722 99.871 99.976 99.904 100.450 99.160 99.184 Atoms per formula unit (4 cations, 6 oxygens) Si 1.828 1.853 1.835 1.817 1.811 1.810 1.899 1.890 1.903 1.892 1.822 Ti 0.007 0.005 0.012 0.012 0.014 0.012 0.008 0.007 0.005 0.007 0.010 Al 0.535 0.541 0.227 0.262 0.221 0.266 0.150 0.178 0.134 0.153 0.347 Fe 3+ 0.086 0.078 0.145 0.127 0.182 0.141 0.094 0.083 0.087 0.095 0.077 Fe 2+ 0.072 0.076 0.153 0.174 0.118 0.162 0.174 0.201 0.186 0.185 0.231 Mn 0.001 0.001 0.002 0.003 0.003 0.002 0.001 0.003 0.003 0.002 0.003 Mg 0.529 0.498 0.716 0.716 0.748 0.717 0.771 0.731 0.774 0.742 0.693 Ca 0.650 0.614 0.845 0.844 0.851 0.838 0.842 0.850 0.870 0.875 0.731 Na 0.292 0.335 0.066 0.046 0.052 0.052 0.060 0.056 0.037 0.047 0.087 K 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 Sum 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 4.000 96 MICROPROBE ANALYSES OF PLAGIOCLASE FROM ECLOGITE SAMPLE CP-47 G2 - P1 CPX1 - P1 CPX1 - P2 CPX1 - P3 CPX1 - P4 CPX1 - P5 CPX1 - P6 CPX2 - P1 CPX2 - P2 CPX2 - P3 Weight % oxide SiO2 57.402 59.724 59.117 61.342 60.052 60.505 60.798 57.962 59.875 60.485 Al2O3 28.354 26.077 26.105 24.858 25.314 25.620 25.215 26.485 26.169 25.329 FeO 0.280 0.207 0.195 0.182 0.232 0.140 0.191 0.139 0.220 0.232 CaO 8.748 6.582 6.616 5.738 6.190 6.126 6.276 7.183 6.917 6.627 Na2O 6.110 7.302 7.435 8.187 7.796 7.983 7.985 7.328 7.104 7.060 K2O 0.144 0.175 0.133 0.174 0.145 0.184 0.174 0.139 0.132 0.160 Total 101.038 100.066 99.602 100.481 99.727 100.558 100.639 99.235 100.417 99.893 Atoms per formula unit (5 cations, 8 oxygens) Si 2.543 2.655 2.643 2.712 2.679 2.677 2.689 2.609 2.653 2.688 Al 1.481 1.366 1.376 1.295 1.331 1.336 1.314 1.405 1.366 1.327 Fe 0.010 0.008 0.007 0.007 0.009 0.005 0.007 0.005 0.008 0.009 Ca 0.415 0.314 0.317 0.272 0.296 0.290 0.297 0.346 0.328 0.316 Na 0.525 0.629 0.645 0.702 0.674 0.685 0.685 0.639 0.610 0.608 K 0.008 0.010 0.008 0.010 0.008 0.010 0.010 0.008 0.007 0.009 Sum 4.983 4.982 4.995 4.997 4.997 5.003 5.002 5.013 4.973 4.957 97 MICROPROBE ANALYSES OF GARNETS FROM ECLOGITE SAMPLE CP-47 G1 - C1 G1 - R2 G1 - C2 G1 - C3 G1 - R3 G1 - C4 G3 - C1 G3 - R1 G3 - C2 G3 - R2 G2 - C1 G2 - R1 G2 - R2 G2 - R3 G2 - C2 Weight % oxide SiO2 39.460 39.532 39.493 40.096 39.369 39.685 39.413 39.528 38.984 38.820 38.784 38.238 38.239 39.332 39.461 TiO2 0.087 0.010 0.079 0.053 0.034 0.027 0.073 0.042 0.031 0.049 0.048 0.046 0.004 0.097 0.065 Al2O3 22.437 22.267 22.475 22.439 21.920 22.131 22.183 21.927 21.907 22.523 23.185 22.626 22.810 23.339 23.304 FeO 18.908 23.262 19.954 19.411 24.141 20.682 19.275 22.612 18.930 23.696 18.503 22.125 21.605 18.449 18.666 MnO 0.350 0.521 0.347 0.313 0.578 0.324 0.287 0.499 0.302 0.576 0.291 0.555 0.510 0.297 0.326 MgO 7.388 7.205 7.094 7.344 7.157 7.706 7.282 6.981 7.227 8.039 8.122 7.420 7.735 7.956 8.190 CaO 11.046 7.785 10.904 10.836 7.063 9.418 11.206 8.434 11.110 6.224 11.189 8.248 8.440 11.238 10.881 Na2O 0.005 0.000 0.000 0.000 0.000 0.000 0.005 0.048 0.068 0.018 0.023 0.000 0.000 0.006 0.000 K2O 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 Total 99.681 100.583 100.346 100.494 100.262 99.974 99.724 100.070 98.559 99.945 100.146 99.258 99.343 100.714 100.892 Atoms per formula unit (8 cations, 12 oxygens) Si 3.008 3.019 3.001 3.036 3.024 3.025 3.007 3.033 3.007 2.975 2.927 2.947 2.936 2.954 2.958 Ti 0.005 0.001 0.005 0.003 0.002 0.002 0.004 0.002 0.002 0.003 0.003 0.003 0.000 0.005 0.004 Al 2.016 2.004 2.013 2.003 1.985 1.988 1.995 1.983 1.991 2.034 2.062 2.055 2.064 2.066 2.059 Fe 3+ 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.002 0.013 0.082 0.046 0.064 0.015 0.018 Fe 2+ 1.206 1.486 1.268 1.229 1.551 1.319 1.230 1.451 1.219 1.505 1.086 1.380 1.323 1.144 1.152 Mn 0.023 0.034 0.022 0.020 0.038 0.021 0.019 0.032 0.020 0.037 0.019 0.036 0.033 0.019 0.021 Mg 0.840 0.820 0.804 0.829 0.820 0.876 0.828 0.798 0.831 0.919 0.914 0.852 0.885 0.891 0.915 Ca 0.902 0.637 0.888 0.879 0.581 0.769 0.916 0.693 0.918 0.511 0.905 0.681 0.694 0.904 0.874 Na 0.001 0.000 0.000 0.000 0.000 0.000 0.001 0.007 0.010 0.003 0.003 0.000 0.000 0.001 0.000 K 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 Sum 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 8.000 98 APPENDIX C 40Ar/39Ar ISOTOPIC AGE DATA 99 Appendix C contains argon isotope data collected on June 13, 2007 at the Auburn Noble Isotope Mass Analysis Laboratory (ANIMAL) performed at Auburn University, under the supervision of Dr. Bill Hames. Both Single Crystal Total Fusion and Incremental heating methods were used to date phlogopite grains separated from lamprophyre dike samples, M-14C and M-21. The appendix also includes data from air samples and monitor data, which were used to estimate the neutron flux parameter, J. The monitor mineral FC-2 (from a split prepared by New Mexico Tech) was used to determine J-values (see McDougall and Harrison, 1999) with the age of 28.02 Ma assigned to FC-2 (after Renee et al., 1998). All argon fraction data are recorded in moles. Table headings for argon fractions are reported in the following list. 40Ar (*, atm) ? Radiogenic 40Ar derived from natural decay of 40K and the atmosphere 39Ar (K) ? 39Ar derived from irradiation 38Ar (Cl, atm) ? 38Ar derived from chlorine and the atmosphere 37Ar (Ca) ? 37Ar derived from calcium 36Ar (atm) ? 36Ar derived from the atmosphere The following paragraphs contain an analytical description of the ANIMAL facility. The facility is equipped with an ultra-high vacuum, 90-degree sector, 10 cm radius spectrometer optimized for 40Ar/39Ar research (single-crystal and multigrain sample incremental heating). The spectrometer employs second-order focusing (Cross, 1951), and is fitted with a high sensitivity electron-impact source and a single ETP electron multiplier (with signal amplification through a standard pre-amplifier). Analyses are typically made using a filament current of 2.75 A, and potentials for the source and 100 multiplier of 2000 V and -1300 V, respectively. The total volume of the spectrometer is 400 cc. 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 comprise 10 cycles of measurement over the range of masses and half-masses from m/e=40 to m/e=35.5, and baseline corrected values are extrapolated to the time of inlet, or averaged, depending upon signal evolution. 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 under computer control. Pumping of residual and sample reactive gases is accomplished through use of SAES AP-10 non-evaporable getters. Pressures in the spectrometer and extraction line, as measured with an ionization gauge, are routinely below ~5x10-9 torr. A pipette delivers standard aliquots of air for use in measuring sensitivity and mass discrimination. Typical recent measurements of 40Ar/36Ar in air are ~ 293 (e.g., from 5/15/07 ? 5/23/07 mass discrimination was 0.9945?0.00038 per amu, at the 95% confidence level for twelve measurements). The extraction line is fitted with a 50W Synrad CO2 IR laser for heating and fusing silicate minerals and glasses. 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 101 line. (The time required to inlet, or equilibrate, a ?half-split? of a sample is less than 7 s, and the inlet time for a full sample is ca. 20 s.) Typical blanks for the entire system (4 minute gettering time) are as follows (in moles): 40Ar, 7.6x10-17; 39Ar, 1.3x10-17; 38Ar, 2.8x10-18; 37Ar, 2.0x10-18; 36Ar, 1.2x10-18. Computer control of the laser, positioning of laser optics, extraction line, mass spectrometer, and data recording is enabled with National Instruments hardware and a Labview program written by lab personnel specifically for ANIMAL. Initial data reduction is accomplished through an in-house Excel spreadsheet, with final reduction using Isoplot (Ludwig, 2003). Figures drawn using Isoplot were constructed using uncertainties of 1?. 102 M-14C SINGLE CRYSTAL TOTAL FUSION (J-Value = 0.01341) 40Ar (*, atm) 39Ar (K) 38Ar (Cl, atm) 37Ar (Ca) 36Ar (atm) %Rad R Age (Ma) 41 2.031E-14 ? 2.1E-17 1.751E-15 ? 3.7E-18 4.63E-18 ? 7.0E-20 1.16E-17 ? 7.5E-19 8.3E-19 ? 8.678E-20 0.988 11.453 260.8 ? 0.7 42 2.176E-14 ? 1.5E-17 1.900E-15 ? 1.7E-18 4.75E-18 ? 9.1E-20 1.72E-17 ? 8.8E-19 7.9E-19 ? 6.710E-20 0.989 11.327 258.1 ? 0.4 43 5.870E-14 ? 8.3E-17 5.152E-15 ? 1.2E-17 1.23E-17 ? 1.1E-19 3.40E-17 ? 1.2E-18 5.9E-19 ? 6.730E-20 0.997 11.359 258.8 ? 0.7 44 4.575E-14 ? 3.6E-17 3.984E-15 ? 9.0E-18 1.20E-17 ? 1.2E-19 2.53E-17 ? 1.4E-18 1.2E-18 ? 7.823E-20 0.992 11.395 259.6 ? 0.6 45 5.855E-14 ? 1.1E-16 5.039E-15 ? 9.8E-18 1.24E-17 ? 5.5E-20 2.41E-17 ? 9.3E-19 1.7E-18 ? 9.059E-20 0.991 11.518 262.2 ? 0.7 46 4.874E-14 ? 5.2E-17 4.197E-15 ? 6.2E-18 1.07E-17 ? 1.5E-19 2.69E-17 ? 1.1E-18 1.0E-18 ? 7.679E-20 0.994 11.542 262.7 ? 0.5 47 1.009E-13 ? 9.6E-17 8.789E-15 ? 1.3E-17 2.48E-17 ? 2.2E-19 9.12E-17 ? 2.4E-18 2.3E-18 ? 1.120E-19 0.993 11.410 259.9 ? 0.5 48 4.144E-14 ? 4.7E-17 3.579E-15 ? 7.1E-18 9.54E-18 ? 1.2E-19 2.15E-17 ? 1.0E-18 2.5E-18 ? 8.740E-20 0.982 11.372 259.1 ? 0.6 49 6.169E-14 ? 7.7E-17 5.337E-15 ? 6.3E-18 1.41E-17 ? 1.1E-19 3.28E-16 ? 2.9E-18 2.1E-18 ? 8.103E-20 0.990 11.445 260.6 ? 0.5 Total Gas Age: 257.2 Ma Weighted Mean Age: 260.0?1.2 Ma 103 M-21 SINGLE CRYSTAL TOTAL FUSION (J-Value = 0.01341) 40Ar (*, atm) 39Ar (K) 38Ar (Cl, atm) 37Ar (Ca) 36Ar (atm) %Rad R Age (Ma) 51 2.379E-14 ? 2.3E-17 2.016E-15 ? 4.6E-18 2.80E-18 ? 1.1E-19 6.25E-17 ? 2.0E-18 2.1E-18 ? 7.757E-20 0.973 11.486 261.5 ? 0.7 52 5.969E-14 ? 3.7E-17 4.993E-15 ? 4.7E-18 1.41E-17 ? 1.1E-19 9.94E-17 ? 1.1E-18 5.5E-18 ? 1.115E-19 0.973 11.630 264.6 ? 0.3 53 5.553E-15 ? 7.8E-18 4.617E-16 ? 1.8E-18 1.08E-18 ? 5.4E-20 2.18E-18 ? 7.4E-19 6.8E-19 ? 1.436E-19 0.964 11.595 263.8 ? 2.4 54 4.620E-14 ? 7.5E-17 3.877E-15 ? 5.2E-18 1.01E-17 ? 8.7E-20 1.18E-16 ? 2.6E-18 3.9E-18 ? 1.026E-19 0.975 11.615 264.2 ? 0.6 55 1.179E-13 ? 1.2E-16 9.955E-15 ? 1.7E-17 2.84E-17 ? 2.8E-19 2.84E-16 ? 2.9E-18 1.3E-17 ? 1.623E-19 0.968 11.461 261.0 ? 0.6 56 1.254E-13 ? 1.8E-16 1.005E-14 ? 2.7E-17 3.12E-17 ? 1.6E-19 4.90E-16 ? 7.1E-18 2.9E-17 ? 2.808E-19 0.932 11.622 264.4 ? 0.9 57 2.735E-14 ? 3.1E-17 2.253E-15 ? 7.3E-18 6.52E-18 ? 9.0E-20 3.50E-17 ? 1.1E-18 4.2E-18 ? 1.097E-19 0.955 11.591 263.7 ? 1.0 58 4.616E-14 ? 8.3E-17 3.874E-15 ? 6.1E-18 1.11E-17 ? 1.3E-19 7.45E-17 ? 2.2E-18 4.6E-18 ? 9.034E-20 0.971 11.565 263.2 ? 0.7 59 8.897E-14 ? 5.7E-17 7.542E-15 ? 6.7E-18 2.02E-17 ? 1.5E-19 2.34E-16 ? 2.8E-18 3.9E-18 ? 1.127E-19 0.987 11.644 264.8 ? 0.3 Total Gas Age: 260.4 Ma Weighted Mean Age: 263.9?1.1 Ma 104 M-14C INCREMENTAL HEATING (J-Value = 0.01341) 40Ar (*, atm) 39Ar (K) 38Ar (Cl, atm) 37Ar (Ca) 36Ar (atm) %Rad R Age (Ma) 3.5 1.156E-16 ? 2.3E-18 4.190E-18 ? 6.3E-19 1.17E-19 ? 7.9E-20 1.95E-19 ? 1.1E-18 2.48E-19 ? 8.1E-20 36.7% 10.127 232.5 ? 173.7 3.8 2.096E-16 ? 3.3E-18 1.508E-17 ? 4.2E-19 3.11E-19 ? 7.3E-20 3.84E-18 ? 1.3E-18 1.40E-19 ? 7.3E-20 80.3% 11.161 254.6 ? 34.4 4.1 5.598E-16 ? 2.9E-18 4.162E-17 ? 6.9E-19 4.19E-19 ? 8.7E-20 6.79E-18 ? 1.5E-18 4.31E-19 ? 7.8E-20 77.3% 10.392 238.2 ? 13.9 4.5 3.241E-15 ? 6.4E-18 2.810E-16 ? 7.2E-19 1.13E-18 ? 3.3E-20 5.50E-18 ? 1.2E-18 3.82E-19 ? 7.2E-20 96.5% 11.130 253.9 ? 1.9 4.9 1.328E-14 ? 1.8E-17 1.140E-15 ? 2.2E-18 3.35E-18 ? 6.7E-20 8.41E-18 ? 1.1E-18 3.71E-19 ? 7.6E-20 99.2% 11.548 262.8 ? 0.8 5.3 1.801E-14 ? 3.0E-17 1.555E-15 ? 4.3E-18 3.27E-18 ? 5.8E-20 2.06E-17 ? 1.6E-18 3.29E-19 ? 1.1E-19 99.5% 11.519 262.2 ? 1.0 5.6 2.775E-14 ? 2.7E-17 2.414E-15 ? 6.9E-18 5.55E-18 ? 5.9E-20 2.83E-17 ? 1.4E-18 2.85E-19 ? 1.0E-19 99.7% 11.461 261.0 ? 0.8 5.9 3.903E-14 ? 3.6E-17 3.413E-15 ? 1.0E-17 5.73E-18 ? 7.3E-20 3.57E-17 ? 1.5E-18 3.81E-19 ? 6.0E-20 99.7% 11.402 259.7 ? 0.8 6.2 9.851E-15 ? 1.2E-17 8.487E-16 ? 4.7E-18 1.69E-18 ? 3.7E-20 1.13E-17 ? 1.0E-18 2.06E-19 ? 6.4E-20 99.4% 11.536 262.6 ? 1.6 6.5 1.557E-14 ? 1.4E-17 1.345E-15 ? 4.8E-18 2.98E-18 ? 7.4E-20 3.77E-18 ? 9.4E-19 2.89E-19 ? 9.7E-20 99.5% 11.516 262.1 ? 1.1 7 1.103E-15 ? 2.4E-18 9.469E-17 ? 9.7E-19 2.74E-19 ? 3.7E-20 9.51E-19 ? 8.1E-19 8.81E-20 ? 6.3E-20 97.6% 11.378 259.2 ? 5.3 Total Gas Age: 257.8 Ma Weighted Mean Age: 261.3?1.4 Ma Plateau Age: 261.56?0.38 Ma 105 M-21 INCREMENTAL HEATING (J-Value = 0.01341) 40Ar (*, atm) 39Ar (K) 38Ar (Cl, atm) 37Ar (Ca) 36Ar (atm) %Rad R Age (Ma) 3.5 8.580E-15 ? 1.3E-17 2.521E-16 ? 2.7E-18 4.77E-18 ? 3.3E-19 9.16E-17 ? 1.9E-18 1.93E-17 ? 2.2E-19 33.6% 11.446 260.7 ? 11.7 3.8 8.880E-15 ? 1.6E-17 6.896E-16 ? 5.0E-18 2.05E-18 ? 5.9E-20 7.60E-18 ? 7.3E-19 3.12E-18 ? 1.2E-19 89.6% 11.542 262.7 ? 2.5 4.1 1.620E-14 ? 1.7E-17 1.300E-15 ? 4.6E-18 3.84E-18 ? 8.8E-20 8.19E-18 ? 8.3E-19 3.96E-18 ? 1.4E-19 92.8% 11.568 263.2 ? 1.3 4.5 1.906E-14 ? 1.8E-17 1.627E-15 ? 3.7E-18 3.85E-18 ? 4.6E-20 1.53E-17 ? 6.5E-19 5.83E-19 ? 1.2E-19 99.1% 11.609 264.1 ? 0.8 4.8 2.358E-14 ? 2.8E-17 2.027E-15 ? 3.0E-18 4.97E-18 ? 8.1E-20 1.87E-17 ? 9.7E-19 5.23E-19 ? 1.1E-19 99.3% 11.558 263.0 ? 0.6 5.1 2.040E-14 ? 1.9E-17 1.745E-15 ? 4.5E-18 4.23E-18 ? 4.3E-20 1.60E-17 ? 1.1E-18 2.75E-19 ? 6.7E-20 99.6% 11.641 264.8 ? 0.8 5.6 3.305E-14 ? 2.4E-17 2.817E-15 ? 1.1E-17 6.86E-18 ? 8.8E-20 7.54E-17 ? 1.7E-18 5.56E-19 ? 7.0E-20 99.5% 11.672 265.5 ? 1.1 5.9 3.635E-15 ? 3.9E-18 3.047E-16 ? 1.5E-18 9.90E-19 ? 4.6E-20 1.44E-17 ? 9.0E-19 1.19E-19 ? 6.4E-20 99.0% 11.815 268.5 ? 2.0 6.2 1.020E-16 ? 1.6E-18 1.012E-17 ? 5.1E-19 1.89E-19 ? 8.3E-20 2.96E-18 ? 8.5E-19 1.11E-19 ? 6.6E-20 67.8% 6.833 160.1 ? 47.5 6.5 2.993E-17 ? 2.5E-18 2.164E-18 ? 6.6E-19 -6.46E-22 ? -4.7E-21 2.04E-18 ? 9.2E-19 -1.89E-20 ? -5.9E-20 118.7% 16.411 363.0 ? 197.5 Total Gas Age: 261.1 Ma Weighted Mean Age: 264.1?1.1 Ma Plateau Age: 263.93?0.37 Ma 106 SAMPLE FC-2 MONITOR DATA 40Ar (*, atm) 39Ar (K) 38Ar (Cl, atm) 37Ar (Ca) 36Ar (atm) %Rad R J Value a 5.238E-14 ? 3.1E-17 4.439E-14 ? 3.5E-17 1.06E-16 ? 7.3E-19 3.34E-16 ? 4.6E-18 1.72E-18 ? 8.8E-20 99.0% 1.168 0.01340 ? 1.518E-05 b 5.469E-14 ? 3.3E-17 4.646E-14 ? 2.3E-17 1.28E-16 ? 8.1E-19 4.54E-16 ? 2.8E-18 2.29E-18 ? 9.7E-20 98.8% 1.163 0.01346 ? 1.304E-05 c 6.602E-14 ? 7.5E-17 5.450E-14 ? 5.2E-17 1.83E-16 ? 1.2E-18 6.82E-16 ? 4.2E-18 7.57E-18 ? 1.1E-19 96.6% 1.170 0.01337 ? 2.181E-05 d 1.084E-13 ? 1.1E-16 9.121E-14 ? 6.8E-17 2.45E-16 ? 6.8E-19 5.55E-16 ? 6.2E-18 9.47E-18 ? 1.5E-19 97.4% 1.158 0.01352 ? 1.815E-05 e 1.122E-13 ? 3.5E-17 9.293E-14 ? 4.1E-17 2.38E-16 ? 1.0E-18 5.75E-16 ? 5.4E-18 9.90E-18 ? 2.1E-19 97.4% 1.175 0.01332 ? 1.071E-05 Mean 0.01341 ? 3.469E-05 MEASUREMENTS OF ARGON ISOTOPES IN AIR 40Ar (*, atm) 39Ar (K) 38Ar (Cl, atm) 37Ar (Ca) 36Ar (atm) (40/36) (40/38) M. Fract a 6.950E-14 + 8.7E-17 -3.583E-18 + 3.6E-19 4.32E-17 + 3.6E-19 -1.89E-19 + 1.5E-19 2.32E-16 + 1.5E-18 299.69 1607.53 1.0035 b 7.145E-14 + 1.4E-16 -4.307E-18 + 4.2E-19 4.47E-17 + 5.7E-19 -2.50E-19 + 1.9E-19 2.35E-16 + 1.1E-18 303.43 1597.12 1.0067 c 7.128E-14 + 9.8E-17 -5.515E-18 + 1.2E-18 4.48E-17 + 5.7E-19 1.21E-19 + 1.6E-19 2.37E-16 + 1.2E-18 300.33 1590.94 1.0041 d 1.215E-13 + 1.5E-16 1.708E-18 + 1.5E-18 7.75E-17 + 1.2E-18 1.02E-18 + 1.2E-19 4.05E-16 + 1.9E-18 299.55 1566.58 1.0034 e 6.574E-14 + 6.4E-17 -5.893E-19 + 6.6E-19 4.19E-17 + 1.3E-18 2.81E-19 + 1.2E-19 2.19E-16 + 5.7E-19 300.21 1567.64 1.0040