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The Mccullough Pass Caldera, Clark County, Nevada UNLV Retrospective Theses & Dissertations 1-1-2000 Evolution of a small silicic system: The McCullough Pass Caldera, Clark County, Nevada Aaron Lee Sanford University of Nevada, Las Vegas Follow this and additional works at: https://digitalscholarship.unlv.edu/rtds Repository Citation Sanford, Aaron Lee, "Evolution of a small silicic system: The McCullough Pass Caldera, Clark County, Nevada" (2000). UNLV Retrospective Theses & Dissertations. 1224. http://dx.doi.org/10.25669/4e8p-m2rk This Thesis 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 Thesis 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 Thesis 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]. INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer. 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 bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMI 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. Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand comer and continuing from left to right in equal sections with small overlaps. Photographs included in the original manuscript have been reproduced xerographically in this copy. Higher quality 6" x 9” black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order. Bell & Howell Information and Leaming 300 North Zeeb Road, Ann Arbor, Ml 48106-1346 USA 800-521-0600 UMI’ Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. EVOLUTION OF A SMALL SILICIC SYSTEM: THE MCCULLOUGH PASS CALDERA, CLARK COUNTY, NEVADA by Aaron Lee Sanford Bachelor of Science University of Idaho 1997 A thesis submitted in partial fulfillment of the requirements for the Master of Science Degree Department of Geoscience College of Sciences Graduate College University of Nevada, Las Vegas December 2000 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UMI Number 1403097 UMI* UMI Microform 1403097 Copyright 2001 by Bell & Howell Information and Leaming Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. Bell & Howell Information and Leaming Company 300 North Zeeb Road P.O. Box 1346 Ann Arbor, Ml 48106-1346 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Thesis Approval IINTV The Graduate C ollege University of Nevada, Las Vegas December 11______ , 2000 The Thesis prepared by Aaron Lee Sanford E ntitled Evolution of a Small Silicic System: The McCullough Pass Caldera. Clark County. Nevada is approved in partial fulfillment of the requirements for the degree of Master of Science in Geoscience Examination Committee Chair Dean of the Graduate College tee Member Graduate Couege-Faculty Representative PR/1017-B/1-00 u Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ABSTRACT Evolution of a Small Silicic System: The McCullough Pass Caldera, Clark County, Nevada by Aaron Lee Sanford Dr. Eugene I. Smith, Examination Committee Chair Professor of Geoscience University of Nevada, Las Vegas The McCullough Pass Caldera is a small caldera in southern Nevada formed by the eruption of the McCullough Pass rhyolites. The McCullough Pass rhyolites erupted as three successive rhyolitic magma batches from 14.12 to 13.98 Ma and produced the McCullough Pass caldera. Each magma batch was chemically zoned by sidewall crystallization prior to erupting. The first magma batch erupted to produce the McCullough Pass tuff and caused collapse of the Jean Lake caldera along a ring fracture identified by the pattern of Jean Lake domes. The second magma batch produced the Ramhead rhyolite and resulted in collapse of the Ramhead caldera. The third magma batch produced dikes, domes and flows of the Capstone rhyolite, which produced a topographic high. The topographic high prohibited Hidden Valley andésite, which erupted from a cinder cone field surrounding the McCullough Pass caldera, from flowing into the caldera. After volcanism had ended, preferential erosion of the McCullough Pass rhyolites produced the present topographic low known as the McCullough Pass caldera. in Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS ABSTRACT.......................................................................................................................ni LIST OF FIGURES AND TABLES.................................................................................. vi ACKNOWLEDGEMENTS.............................................................................................. vii CHAPTER 1 INTRODUCTION.......................................................................................1 Purpose of Thesis ........................................................................................................1 Regional Setting ......................................................................................................... 2 Previous Work ............................................................................................................ 2 CHAPTER 2 MCCULLOUGH RANGE.......................................................................... 7 Stratigraphy ................................................................................................................ 7 Volcanic Centers in the McCullough Range .............................................................. 9 Structure................................................................................................................... 10 CHAPTER 3 THE MCCULLOUGH PASS CALDERA............................................... 13 Physical Characteristics .............................................................................................13 Intracaldera Stratigraphy ........................................................................................... 16 CHAPTER 4 GEOCHRONOLOGY...............................................................................18 CHAPTERS GEOCHEMISTRY................................................................................... 33 CHAPTER 6 PETROGRAPHY...................................................................................... 44 CHAPTER 7 PETROGENESIS ...................................................................................... 46 Origin of Basaltic Magma ........................................................................................ 46 Origin of RhyoUtic Magmas .................................................................................... 47 Petrogenetic Model .................................................................................................. 49 Magma Batch Models .............................................................................................. 50 CHAPTER 8 PHYSICAL EVOLUTION OF THE MCCULLOUGH PASS CALDERA................................................................................................ 69 CHAPTER 9 COMPARISON OF MPC TO OTHER SILICIC SYSTEMS.................. 72 Small Süicic Systems................................................................................................72 Large Silicic Systems................................................................................................74 IV Reproduced witti permission of ttie copyrigfit owner. Furtfier reproduction profiibited witfiout permission. CHAPTER 10 CONCLUSIONS..................................................................................... 79 REFERENCES CITID..................................................................................................... 80 APPENDIX 1 ANALYTICAL TECHNIQUES.............................................................87 APPENDIX 2 ■’W ^ A tDATA ...................................................................................... 93 APPENDIX 3 GEOCHEMISTRY DATA......................................................................99 APPENDIX 4 ISOTOPE DATA....................................................................................107 APPENDIX 5 DISTRIBUTION COEFFICIENTS...................................................... 109 VITA................................................................................................................................I
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