Age and Tectonic Evolution of the Amdo Basement: Implications for Development of the Tibetan Plateau and Gondwana Paleogeography
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Age and Tectonic Evolution of the Amdo Basement: Implications for Development of the Tibetan Plateau and Gondwana Paleogeography Item Type text; Electronic Dissertation Authors Guynn, Jerome Publisher The University of Arizona. Rights Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Download date 09/10/2021 06:21:37 Link to Item http://hdl.handle.net/10150/195951 AGE AND TECTONIC EVOLUTION OF THE AMDO BASEMENT: IMPLICATIONS FOR DEVELOPMENT OF THE TIBETAN PLATEAU AND GONDWANA PALEOGEOGRAPHY by Jerome Hamilton Guynn _________________________ A Dissertation Submitted to the Faculty of the DEPARTMENT OF GEOSCIENCES In Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY In the Graduate College THE UNIVERSITY OF ARIZONA 2006 2 THE UNIVERSITY OF ARIZONA GRADUATE COLLEGE As members of the Dissertation Committee, we certify that we have read the dissertation prepared by Jerome Guynn entitled “Age and Tectonic Evolution of the Amdo Basement: Implications for Development of the Tibetan Plateau and Gondwana Paleogeography” and recommend that it be accepted as fulfilling the dissertation requirement for the Degree of Doctor of Philosophy _______________________________________________________________________ Date: 11/20/06 Dr. Paul Kapp _______________________________________________________________________ Date: 11/20/06 Dr. Pete DeCelles _______________________________________________________________________ Date: 11/20/06 Dr. George Zandt _______________________________________________________________________ Date: 11/20/06 Dr. Mihai Ducea _______________________________________________________________________ Date: 11/20/06 Dr. Clem Chase Final approval and acceptance of this dissertation is contingent upon the candidate’s submission of the final copies of the dissertation to the Graduate College. I hereby certify that I have read this dissertation prepared under my direction and recommend that it be accepted as fulfilling the dissertation requirement. ________________________________________________ Date: 11/20/06 Dissertation Director: Dr. Paul Kapp 3 STATEMENT BY AUTHOR This dissertation has been submitted in partial fulfillment of requirements for an advanced degree at the University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library. Brief quotations from this dissertation are allowable without special permission, provided that accurate acknowledgment of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be grated by the head of the major department or the Dean of the Graduate College when in his or her judgment the proposed use of the material is in the interests of scholarship. In all other instances, however, permission must be obtained from the author. Signed: Jerome H. Guynn 4 ACKNOWLEDGMENTS Many, many people have supported me throughout the last seven years as I switched careers from engineering to geology. First and foremost is my mom, Trish Casper, who wholly supported my decision to go back to school and has always been there to talk to during bumps along the way. My sister, Sierra, and I have been in graduate school about the same time as me and so she has been a great resource and a wonderful support during this time. She also was the first to suggest I go back to school in geology after the great trip we had to New Zealand. My friend, Mimi Ashcraft, has always wanted me to pursue geology, ever since I earned the geology merit badge with her in high school. She is always interested in hearing about my research and has been highly supportive. I want to give a big “thank you” to my advisor, Paul Kapp, who has provided me with opportunities, advice, constructive criticism and encouragement throughout the time I have earned my Ph.D. He has always been available for discussing my research and helping me through problems and I have learned a great deal about doing science from him. I have also learned a lot from Pete DeCelles, in classes, in the field and in discussions about Himalayan and Tibetan geology. George Gehrels has been a great help and I am indebted to him for his time and assistance with U-Pb geochronology, which has formed a large part of my research. I would also like to thank my other committee members: George Zandt, Mihai Ducea and Clem Chase. I also want to thank Matt Heizler of New Mexico Tech for his 40Ar/39Ar analyses. Finally, I thank Ding Lin of the Chinese Academy of Sciences in Beijing for his support with our field work, including permits, colleagues and travel arrangements. A special “thanks” goes to Alex Pullen and Ross Waldrip who assisted me in the field in Tibet. John Volkmer, Shundong He and Ross Waldrip have been terrific graduate student colleagues and friends. Other fellow graduate students and undergraduates who have provided assistance and discussion include Joel Saylor, Dave Pearson, Jen Fox, Jen McGraw, Kelley Stair and Jen Pullen. Ken Dominik of the Lunar and Planetary Laboratory provided invaluable assistance with the electron microprobe. My roommates for the past year and a half, Kevin Anchukaitis and Tm Shanahan, have been a great support as we have all struggled through finishing our Ph.D. I will miss the commiserating and comradery that we have shared over many beers and burgers at Gentle Ben’s the past year. Thanks to Katie Davis for our many conversations and the good advice she always has. I also have a long list of Arizona friends who have been very supportive and a great social network for escaping the craziness of grad school. Many thanks to Aly, Andy, Anna, Britt, Dave, Jessica R., Jessica C., Kevin J., Lynette, Scott, Toby, Tom, Megan, Lara, Tashana, Jana and Morgen. 5 DEDICATION This dissertation is dedicated to my mom, Trish Hamilton Casper; my sister, Dr. Sierra Guynn; and my friend, Mimi Ashcraft. 6 TABLE OF CONTENTS ABSTRACT....................................................................................................................12 INTRODUCTION..........................................................................................................13 PRESENT STUDY.........................................................................................................17 Timing of Bangong suture tectonics as revealed by the Amdo basement...........17 Metamorphism of the Amdo basement..................................................................18 Jurassic and Cretaceous evolution of the Bangong suture...................................19 Geochronology of the Amdo gneisses and paleogeography of the Lhasa and Qiangtang terranes ..................................................................................................20 REFERENCES CITED.................................................................................................21 APPENDIX A: Permission for Reproduction from the Geological Society of America...........................................................................................................................25 APPENDIX A: Tibetan basement rocks near Amdo reveal “missing” Mesozoic tectonism along the Bangong suture, central Tibet ....................................................27 ABSTRACT .............................................................................................................28 INTRODUCTION ...................................................................................................29 GEOLOGY ..............................................................................................................31 GEOCHRONOLOGY ............................................................................................32 HISTORY OF METAMORPHISM AND COOLING ........................................33 DISCUSSION AND CONCLUSIONS ..................................................................35 ACKNOWLEDGEMENTS ...................................................................................37 REFERENCES CITED ..........................................................................................37 7 TABLE OF CONTENTS - Continued FIGURE CAPTIONS ..............................................................................................42 FIGURES..................................................................................................................45 Data Repository Item DR2006094 Supplementary Geochronologic and Thermochronologic Data .......................................................................................49 Summary of analytical methods for zircon and titanite U-Pb analysis (University of Arizona)......................................................................................49 Summary of analytical methods for mica 40Ar/39Ar analyses (University of California, Los Angeles). ...................................................................................50 Summary of analytical methods for hornblende and feldspar 40Ar/39Ar analysis (New Mexico Geochronological Research Laboratory)...................50 K-Feldspar multi-domain diffusion modeling methods .................................51 References Cited.................................................................................................52 Figures and Tables.............................................................................................54