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Comparative Evolution of the Shyok and Yarlung Suture Zones

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Comparative Evolution of the Shyok and Yarlung Suture Zones Comparative Evolution of the Shyok and Yarlung Suture Zones: Implications for the Collision Between India and Eurasia by Nathaniel Borneman A Dissertation Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy Approved February 2016 by the Graduate Supervisory Committee: Kip Hodges, Chair Stephen Reynolds Kelin Whipple Thomas Sharp James Tyburczy ARIZONA STATE UNIVERSITY May 2016 ABSTRACT The collision between the Indian and Eurasian tectonic plates marked the onset of the rise of the Himalayan-Tibetan orogen, but also brought about profound changes to the Earth's oceans and climate. The exact sequence of events that occurred during this collision is poorly understood, leading to a wide range of estimates of its age. The Indus and Yarlung sutures are generally considered to represent the final collision between India and Eurasia, and together form a mostly continuous belt that can be traced over 2000 km along strike. In the western portions of the orogen the Karakoram Fault introduces a key complexity to the study of timing of collision by offsetting the Indus and Yarlung sutures. Recent work has used the complexities introduced by the Karakoram Fault to suggest that the more northerly Shyok suture, not the Indus suture, represents the India-Eurasia collision zone. Estimates for timing of the India-Eurasia collision fall into one of three groups: 40-34 Ma, 55-50 Ma, and 66-60 Ma. Attempts to reconcile these models have thus far been unsuccessful. In order to provide additional data that might further clarify the timing and location of collision, studies have been performed along the Shyok suture in India and along the Yarlung suture in Tibet at Sangsang. A study along the Shyok suture argues that the suture formed between 92-85 Ma. This timing precludes an interpretation that the Shyok suture marks the location of the India-Eurasia collision. A second study demonstrates the utility of two new geochronometers, (U-Th)/Pb joaquinite and 40Ar/39Ar neptunite, that play an important role in unraveling the tectonic history of the Yarlung suture. A third study is an investigation of the structure and geochronology of the Sangsang ophiolite complex. Here, multiple (U-Th)/Pb and 40Ar/39Ar systems record magmatism and metamorphism spanning ca. 125-52 Ma. By i tying these chronometers to tectonic process, a history is reconstructed of the southern margin of Tibet that includes Early Cretaceous to Late Cretaceous forearc rifting associated with mid ocean ridge subduction, Paleocene accretionary wedge uplift and erosion, and finally Eocene metasomatism and collision. ii DEDICATION To Greg King, William Vanca, Jane Burton, and Yolanda Vanca iii ACKNOWLEDGMENTS It seems appropriate to start by thanking my advisor, Kip Hodges, for his countless hours of advising. I would also like to thank my other committee members: Stephen Reynolds, Thomas Sharp, James Tyburczy, and Kelin Whipple, all of whom helped shape my thinking throughout this project. Matthijs van Soest and Jo-Ann Wartho have taught me what I know about analytical lab work, and without them the data that follows would not exist. Hodges group members past and present have greatly helped me along the way: Michele Aigner, Wendy Bohon, Frances Cooper, Sarah Cronk, Alex Horne, Cameron Mercer, Brian Monteleone, Mary Schultz, Alka Tripathy-Lang, and Kelsey Young. I owe gratitude to all of the coauthors of my papers, but special thanks go those who partnered with me directly in the field and endured my antics. Members of the SESE community I owe gratitude to are numerous, and I thank you all. My family has earned recognition for supporting me when I needed it, and for putting up with my long bouts of absence otherwise. Special thanks to Katherine Sheppard for reading and commenting on this entire dissertation. I have been funded throughout my time as a graduate student by the NSF (awards EAR 1007929 (Tectonics) and EAR 0642731 (Sedimentary Geology and Paleobiology)) and by the School of Earth and Space Exploration at ASU. iv TABLE OF CONTENTS Page LIST OF TABLES ................................................................................................................ xiii LIST OF FIGURES ...............................................................................................................xiv CHAPTER 1 INTRODUCTION ................. ........................................................................................... 1 Motivation ................................................................................................ 1 Chapter Outline ........................................................................................ 5 Figure Captions ........................................................................................ 7 References ................................................................................................ 7 2 AGE AND STRUCTURE OF THE SHYOK SUTURE IN THE LADAKH REGION OF NORTHWESTERN INDIA: IMPLICATIONS FOR SLIP ON THE KARAKORAM FAULT SYSTEM .......................................................... 11 Abstract ................................................................................................... 11 Introduction ............................................................................................ 13 Regional Setting ..................................................................................... 15 The Kohistan-Ladakh Block .................................................................. 15 The Karakoram Block ............................................................................ 17 The Shyok Suture and Plausible Correlatives ....................................... 17 Proposed Total Displacements for the Central Karakoram Fault System ........................................................................................... 20 Geology of the Saltoro Range and Results ............................................ 20 Ladakh Block Lithologies ...................................................................... 22 v CHAPTER Page Shyok Suture Zone Volcanic and Sedimentary Units ........................... 22 Shyok Volcanics of the Saltoro Range .................................................. 23 Saltoro Formation ................................................................................... 25 Saltoro Molasse ...................................................................................... 26 Mélange .................................................................................................. 27 Late Intrusive Igneous Rocks Cutting the SSZ ..................................... 27 Karakoram Block Lithologies ................................................................ 28 Correlations with the Shyok Suture Zone ............................................. 29 Structural Geology ................................................................................. 30 Deformational Features of the Ladakh Block ....................................... 30 Khalsar Thrust ........................................................................................ 31 Deformational Features of Stratified and Volcanic Rocks of the Shyok Suture Zone ........................................................................... 32 Murgi Thrust........................................................................................... 33 Deformational Features of the SSZ Mélange Unit ................................ 34 The Waris Thrust .................................................................................... 34 Deformational Features of the Karakoram Block ................................. 35 Deformational Features of the Karakoram Fault System ..................... 36 Geochronology ....................................................................................... 37 40Ar/39Ar Constraints on the Age of the Shyok Volcanics ................... 38 Detrital U/Pb Zircon Constraints on the Provenance and Age of the Saltoro Molasse ................................................................................ 38 vi CHAPTER Page U/Pb LA-ICPMS Zircon Bedrock Geochronology ............................... 41 Karakoram Block Paragneiss ................................................................. 41 Felsic Aplitic Dike Cutting the Shyok Volcanics-Saltoro Molasse Contact ..................................................................................... 42 Granites Intruding the SSZ .................................................................... 43 Late Granodiorite Intruding the Karakoram Block ............................... 44 Discussion and Conclusions .................................................................. 44 Acknowledgments .................................................................................. 52 Figure Captions ...................................................................................... 52 References .............................................................................................. 56 3 EVIDENCE FOR THE EMPLACEMENT AGE OF THE NEW IDRIA SERPENTINITE DIAPIR FROM 40AR/39AR NEPTUNITE AND (U- TH)/PB JOAQUINITE GEOCHRONOLOGY ........................................ 79 Abstract ................................................................................................... 79 Introduction ............................................................................................ 80 Geologic Background ............................................................................ 81 New Constraints on the Age Of
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