UNLV Retrospective Theses & Dissertations 1-1-2007 Thermochronological constraints on Mesozoic tectonism in southwest US and New Zealand; and argon-argon age spectra from artificially mixed micas Joseph Kula University of Nevada, Las Vegas Follow this and additional works at: https://digitalscholarship.unlv.edu/rtds Repository Citation Kula, Joseph, "Thermochronological constraints on Mesozoic tectonism in southwest US and New Zealand; and argon-argon age spectra from artificially mixed micas" (2007). UNLV Retrospective Theses & Dissertations. 2771. http://dx.doi.org/10.25669/ecyt-omvz This Dissertation is protected by copyright and/or related rights. It has been brought to you by Digital Scholarship@UNLV with permission from the rights-holder(s). You are free to use this Dissertation in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s) directly, unless additional rights are indicated by a Creative Commons license in the record and/or on the work itself. This Dissertation has been accepted for inclusion in UNLV Retrospective Theses & Dissertations by an authorized administrator of Digital Scholarship@UNLV. For more information, please contact [email protected]. THERMOCHRONOLOGICAL CONSTRAINTS ON MESOZOIC TECTONISM IN SOUTHWEST U.S. AND NEW ZEALAND; AND '^Ar/^^Ar AGE SPECTRA FROM ARTIFICIALLY MIXED MICAS by Joseph Kula Bachelor of Science, Geoscience Montclair State University 2000 Masters of Science, Geoscience University of Nevada, Las Vegas 2002 A dissertation submitted in partial fulfillment of the requirements for the Doctor of Philosophy Degree in Geoscience Department of Geoscience College of Sciences Graduate College University of Nevada, Las Vegas December 2007 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UMI Number: 3302358 INFORMATION TO USERS The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleed-through, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. UMI UMI Microform 3302358 Copyright 2008 by ProQuest LLC. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. ProQuest LLC 789 E. Eisenhower Parkway PC Box 1346 Ann Arbor, Ml 48106-1346 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Copyright by Joseph Kula 2007 All Rights Reserved Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. T Dissertation Approval The Graduate College University of Nevada, Las Vegas DECEMBER _,2o; 07 The Dissertation prepared by JOSEPH KULA_______________ E n titled THERMOCHPONOLOCTCAL CONSTRAINTS ON MESOZOIC TKCTOWTSM TN SOUTHWEST U.S. AND NEW ZEALAND; AND AnAR/SQAP ACE SPECTRA PPOM ARTTETnTATJ.Y MIXED MTHAS is approved in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY IN GEOSCIENCE I Examination Committee Chair Dean of the Graduate College / / / Examination Committee M eM er Examination Committee Member Graduate College Faculty Representative PR/im7-52/l-00 11 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ABSTRACT Thermochronological constraints on Mesozoic tectonism in southwest U.S. and New Zealand; and '*®Ar/^^Ar age spectra from artificially mixed micas by Joseph Kula Dr. Terry Spell, Examination Committee Chair Associate Professor of Geoscience University of Nevada, Las Vegas Dr. Michael Wells, Examination Committee Co-Chair Professor of Geoscience University of Nevada, Las Vegas The four chapters in this dissertation consist of projects that utilized '^Ar/^^Ar thermochronometry. Chapters 1 and 2 are from a study of the Sisters shear zone on Stewart Island, New Zealand. In these studies, thermal histories obtained using '^^Ar/^^Ar thermochronometry were combined with field and microstructural observations collected from deformed rocks. These data indicate extensional deformation along the Sisters shear zone was the youngest event related to the breakup of the paleo-Gondwana margin. The Sisters shear zone is related to formation of the Great South Basin and thinning of the Campbell Plateau. The shear zone is also spatially and kinematically linked to the Pacific-Antarctic spreading ridge indicating the shear zone was involved in the separation of New Zealand from West Antarctica. Comparison of timing constraints from Stewart Island with those from other studies and locations indicates the breakup of the Gondwana margin was likely the result of two distinct extensional events. Ill Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Chapter 3 consists of a '*°Ar/^^Ar laboratory experiment dealing with the biotite and muscovite micas. Artificial samples of mixed mica populations were analyzed using the vacuum furnace step-heating method. These samples were prepared and analyzed to test the possibility of recovering original ages of individual mica populations from natural samples consisting of multiple generations. The results indicate this is not likely in the vacuum furnace. Additionally, the results indicate that the compositional controls on argon retentivity in nature may also be active during furnace heating in the laboratory. Chapter 4 shows the results of a '*^Ar/^^Ar study of plutonic rocks that have cross cutting relationships with structures of the Clark Mountains thrust complex in southern California. These data indicate the earliest episode of crustal shortening occurred pre- 155 Ma. The Pachalka thrust at -144 Ma was previously considered the oldest deformation episode in the region. Diorite-granodioritic magmatism at -155 Ma was followed closely by felsic magmatism of the Ivanpah granite (>149 Ma). The ductile Morning Star Mine thrust, which likely correlates to the Keaney-Mollusk Mine thrust cuts the Ivanpah granite. IV Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS ABSTRACT.................................................................................................................................. iii LIST OF FIGURES..................................................... vii ACKNOWLEDGMENTS ...........................................................................................viii CHAPTER 1 TWO-STAGE RIFTING OF ZEALANDIA-AUSTRALIA- ANTARCTICA: EVIDENCE FROM ^Ar/^^Ar THERMOCHRONOLOGY OF THE SISTERS SHEAR ZONE, STEWART ISLAND, NEW ZEALAND........................................................ 1 Abstract.................................................;...................................................................................1 Introduction .............................................................................................................................. 2 Sisters shear zone, Stewart Island .........................................................................................3 ''^Ar/^^Ar thermochronometry ............................................................................................... 5 Discussion ................................................................................................................................ 7 Two-stage Zealandia rifting model .......................................................................................9 Figure captions .................................................................................... 10 Figures ..................................................................................................................................... 12 References............................ 14 CHAPTER 2 THERMAL EVOLUTION OF THE SISTERS SHEAR ZONE, SOUTHERN NEW ZEALAND; FORMATION OF THE GREAT SOUTH BASIN AND DRIVING MECHANISMS FOR CONTINENTAL BREAKUP................................................................................................ 18 Abstract.................................................................................................................................... 18 Introduction ..............................................................................................................................19 Stewart Island geology...........................................................................................................20 The Sisters shear zone ...................................... 21 '*'^Ar/^^Ar procedures ........................................................................ 28 ''^Ar/^^Ar results......................................................................................................................30 Discussion .................................................................................... 34 Conclusions ............................................................................................................................. 50 Figure captions ........................................................................................................................50 Figures .....................................................................................................................................