Geology and Mineralization of the Undeveloped Cochise Supergene Porphyry Copper Deposit, Warren (Bisbee) Mining District, Cochise County, Arizona Item Type text; Electronic Thesis Authors Lewis, Kyle Citation Lewis, Kyle. (2021). Geology and Mineralization of the Undeveloped Cochise Supergene Porphyry Copper Deposit, Warren (Bisbee) Mining District, Cochise County, Arizona (Master's thesis, University of Arizona, Tucson, USA). 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, presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Download date 11/10/2021 12:18:59 Item License http://rightsstatements.org/vocab/InC/1.0/ Link to Item http://hdl.handle.net/10150/660212 GEOLOGY AND MINERALIZATION OF THE UNDEVELOPED COCHISE SUPERGENE PORPHYRY COPPER DEPOSIT, WARREN (BISBEE) MINING DISTRICT, COCHISE COUNTY, ARIZONA by Kyle A. Lewis ____________________________ Copyright © Kyle A. Lewis 2021 A Thesis Submitted to the Faculty of the DEPARTMENT OF GEOSCIENCES In Partial Fulfillment of the Requirements For the Degree of PROFESSIONAL SCIENCE MASTERS ECONOMIC GEOLOGY In the Graduate College THE UNIVERSITY OF ARIZONA 2021 1 ACKNOWLEDGMENTS This study was funded by Freeport-McMoRan and inspired by geologists of that company during a field trip to Bisbee and Cochise in the summer of 2019. Many individuals deserve my gratitude for their cooperation and input. Michele Anthony, Mac Canby, and Paul Albers granted me time and permission to complete the field work. Ralph Stegen, Matthew Wetzel, Wolfram Schuh, Carli Balogh, Nicholas Dize, and David First offered their geologic insight and moral support. Christopher Svenson, Rob Williams, and members of the Copper Queen branch in Bisbee looked after my health and safety. I want to thank Ernie Wright in particular for sharing his valuable knowledge of the district that he accumulated via decades of dedicated work. My research would have remained an amorphous, meandering adventure without the guidance of my principal advisor, Dr. Eric Seedorff. It was a true honor to be supervised by someone with his unparalleled “savage geologic competence” (as a former coworker of mine aptly phrased it). Effective scientific communication, the importance of culture and friendship in academia and the minerals industry, and “thinking like a geologist” are principles that will stick with me for my lifetime. Dr. Mark Barton, Dr. Isabel F. Barton, and Dr. Frank Mazdab were also incredibly helpful; I appreciate their time, patience, and dedication to their trade. My colleagues, Dylan Carlini, Eytan Bos Orent, Alec Martin, and Lydia Bailey were terrific companions, especially during the trying times of 2020. I owe much of my remaining sanity to them. My final thanks go to my family, in particular my mother. She is loving and helpful, and she always has open ears and an open mind when I need her advice and reassurance. 3 TABLE OF CONTENTS LIST OF FIGURES AND TABLES ............................................................................................ 6 ABSTRACT ................................................................................................................................... 7 INTRODUCTION......................................................................................................................... 8 LOCATION AND REGIONAL GEOLOGIC SETTING ...................................................... 10 Porphyry copper deposits of southwestern North America ...................................................... 12 HISTORY OF THE WARREN MINING DISTRICT ............................................................ 13 Exploration of the Cochise deposit ........................................................................................... 15 GEOLOGY OF THE WARREN MINING DISTRICT.......................................................... 16 Proterozoic Pinal Schist and Paleozoic strata ......................................................................... 17 The Sacramento Hill intrusive complex (SHIC) ....................................................................... 18 Breccias of the SHIC ................................................................................................................. 20 Other intrusions in the Mule Mountains ................................................................................... 21 Late Jurassic to Early Cretaceous Bisbee Group ..................................................................... 21 Structure .................................................................................................................................... 22 MINERALIZATION OF THE WARREN DISTRICT .......................................................... 24 Carbonate replacement deposits (CRDs) ................................................................................. 24 Mineralization in the Lavender and Sacramento pits ............................................................... 25 METHODS .................................................................................................................................. 26 GEOLOGY AND MINERALIZATION OF THE COCHISE DEPOSIT............................. 27 Rock types ................................................................................................................................. 27 Hypogene alteration .................................................................................................................. 29 Mineralization ........................................................................................................................... 32 Leached cap characteristics (supergene alteration) ................................................................. 33 4 INTERPRETATIONS ................................................................................................................ 35 Sequence of alteration and mineralization ............................................................................... 35 Presence or absence of advanced argillic alteration at Cochise ............................................. 36 Relationship of the Cochise porphyry to Lavender pit intrusions ............................................ 37 The Cochise deposit as the “roots” of Lavender pit porphyry and CRD mineralization ......... 38 Origin of breccias at Cochise ................................................................................................... 39 Copper content of sericite alteration ........................................................................................ 41 Estimation of supergene enrichment factor and volume of leached rock ................................. 43 DISCUSSION .............................................................................................................................. 44 Comparison to other supergene porphyry Cu deposits ............................................................ 44 The paucity of Jurassic porphyry deposits in southwestern North America ............................ 48 Exploration implications ........................................................................................................... 51 CONCLUSIONS ......................................................................................................................... 53 FIGURES AND TABLES .......................................................................................................... 55 APPENDIX A - EXPANDED GEOLOGY, MINERALIZATION, AND HISTORY OF THE WARREN MINING DISTRICT ...................................................................................... 77 Proterozoic Pinal Schist ........................................................................................................... 77 Phanerozoic sedimentary rocks ................................................................................................ 78 The Sacramento Hill intrusive complex (SHIC) ....................................................................... 79 Older quartz porphyry .............................................................................................................. 81 Younger feldspar-quartz porphyry ............................................................................................ 82 Contact / “intrusion” breccia ................................................................................................... 83 Hydrothermal / “intrusive” breccias ........................................................................................ 85 Other intrusions in the Mule Mountains ................................................................................... 86 Structure .................................................................................................................................... 87 Carbonate replacement deposits (CRDs) ................................................................................. 89 Alteration of limestone .............................................................................................................. 91 Disseminated Cu mineralization in the Lavender and Sacramento pits ................................... 92 Alteration in the Lavender pit ................................................................................................... 93 5 REFERENCES ...........................................................................................................................