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Geologic Extremes of the NW Himalaya

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Geologic Extremes of the NW Himalaya Louisiana State University LSU Digital Commons LSU Doctoral Dissertations Graduate School 2016 Geologic Extremes of the NW Himalaya: Investigations of the Himalayan Ultra-high Pressure and Low Temperature Deformation Histories Dennis Girard Donaldson Louisiana State University and Agricultural and Mechanical College Follow this and additional works at: https://digitalcommons.lsu.edu/gradschool_dissertations Part of the Earth Sciences Commons Recommended Citation Donaldson, Dennis Girard, "Geologic Extremes of the NW Himalaya: Investigations of the Himalayan Ultra-high Pressure and Low Temperature Deformation Histories" (2016). LSU Doctoral Dissertations. 3295. https://digitalcommons.lsu.edu/gradschool_dissertations/3295 This Dissertation is brought to you for free and open access by the Graduate School at LSU Digital Commons. It has been accepted for inclusion in LSU Doctoral Dissertations by an authorized graduate school editor of LSU Digital Commons. For more information, please [email protected]. GEOLOGIC EXTREMES OF THE NW HIMALAYA: INVESTIGATIONS OF THE HIMALAYAN ULTRA-HIGH PRESSURE AND LOW TEMPERATURE DEFORMATION HISTORIES A Dissertation Submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Doctor of Philosophy in The Department of Geology and Geophysics by Dennis G. Donaldson Jr. B.S., Virginia State University, 2009 August 2016 Dedicated to Jaime, Eliya, Noah, my siblings and parents. ii ACKNOWLEDGEMENTS I am very pleased that I have had a rewarding journey during this chapter of my life with the Department of Geology and Geophysical at Louisiana State University. I would not be here right now if it wasn’t for Dr. Alex Webb, Dr. Barb Dutrow, Dr. Phil Bart, and the many other colleagues and friends I’ve had the great fortune of meeting. I would like to thank the Louisiana State Board of Regents, as well as the National Science Foundation for funding my research. Words cannot express my gratitude. I would like to thank Rick Young, Andrew Kylander-Clark, Brad Hacker and Carrie Menold for assisting and providing valuable guidance throughout my research. I extend my appreciation to my fellow graduate students, Dian He, Cindy Colon, and the many undergraduates who have been in our cluster. Finally, I would like to express my deep love and gratitude to my wife Jaime, my daughter Eliya and my son Noah. iii TABLE OF CONTENTS ACKNOWLEDGEMENTS.................................................................................................................. iii ABSTRACT ......................................................................................................................................... vi CHAPTER 1 : INTRODUCTION ......................................................................................................... 1 1.1 UHP Metamorphism ............................................................................................................... 1 1.2 Himalayan UHP Metamorphism............................................................................................. 2 1.3 Himalayan Orogenesis ............................................................................................................ 2 1.3.1 Shortening and Development .......................................................................................... 2 1.3.2 Two Collision Greater Indian Basin Model .................................................................... 3 1.3.3 Models of Himalayan Development ................................................................................ 4 CHAPTER 2 : PETROCHRONOLOGY OF ULTRAHIGH-PRESSURE HIMALAYAN ECLOGITE ............................................................................................................................................ 7 2.1 Introduction ............................................................................................................................. 7 2.2 Geologic Setting and Petrology .............................................................................................. 9 2.3 Methods................................................................................................................................. 10 2.4 Petrochronology .................................................................................................................... 11 2.5 Discussion and Conclusions ................................................................................................. 14 CHAPTER 3 : INVESTIGATION OF MULTI-STAGE METAMORPHISM: TSO MORARI, NW HIMALAYAN GEOCHRONOLOGY ............................................................................................... 18 3.1 Introduction ........................................................................................................................... 18 3.1.1 Ultra-high Pressure Metamorphism in the Western Himalaya ...................................... 18 3.1.2 Previous P-T Calculations ............................................................................................. 20 3.1.3 Previous Geochronology ............................................................................................... 21 3.1.4 Rutile and Titanite Geochronology ............................................................................... 22 3.2 Geologic Background ........................................................................................................... 23 3.2.1 Lithologic Descriptions and Petrography ...................................................................... 23 3.3 Methods................................................................................................................................. 28 3.3.1 Geochronology .............................................................................................................. 28 3.4 Results ................................................................................................................................... 29 3.4.1 Geochronology .............................................................................................................. 29 3.5 Discussion ............................................................................................................................. 32 3.5.1 Geochronology .............................................................................................................. 32 3.5.2 Titanite Geochronology ................................................................................................. 32 3.5.3 Rutile Analyses .............................................................................................................. 34 3.6 Conclusions ........................................................................................................................... 34 CHAPTER 4 : INVESTIGATION OF HIMALAYA DEVELOPMENT: SHORTENING AND GHC EMPLACEMENT ............................................................................................................................... 36 4.1 Introduction ........................................................................................................................... 36 4.2 Geologic Background ........................................................................................................... 43 iv 4.2.1 Stratigraphic Units ......................................................................................................... 43 4.2.2 Lower Haimanta ............................................................................................................ 44 4.2.3 The Middle Haimantas .................................................................................................. 44 4.2.4 The Upper Haimantas .................................................................................................... 44 4.2.5 Upper Tethyan Formations ............................................................................................ 44 4.3 Methods................................................................................................................................. 45 4.3.1 Field Mapping................................................................................................................ 45 4.3.2 Microstructural Work .................................................................................................... 58 4.3.3 Line Length Balancing and with Microstructural Strain Data ...................................... 59 4.4 Results ................................................................................................................................... 59 4.4.1 Field Based Mapping and Geology of Study Section AB ............................................. 59 4.4.2 Strain Analysis ............................................................................................................... 63 4.4.3 Microstructures and Regional Structures ...................................................................... 70 4.4.4 Cross Sections................................................................................................................ 72 4.5 Discussion and Conclusions ................................................................................................. 72 4.5.1 Shortening Budget ......................................................................................................... 73 4.5.2 Implications for Extrusion Models ................................................................................ 76 4.5.3
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