Mineralogy, petrology, and genesis of the Lucifer manganese deposit, Santa Rosalia area, Baja California Sur, Mexico Item Type text; Thesis-Reproduction (electronic) Authors Freiberg, Daniel Arthur 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 or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Download date 26/09/2021 09:04:10 Link to Item http://hdl.handle.net/10150/582324 MINERALOGY, PETROLOGY, AND GENESIS OF THE LUCIFER MANGANESE DEPOSIT, SANTA ROSALIA AREA, BAJA CALIFORNIA SUR, MEXICO by Daniel Arthur Freiberg A Thesis Submitted to the Faculty of the DEPARTMENT OF GEOSCIENCES In Partial Fulfillment of the Requirements For the Degree of MASTER OF SCIENCE In The Graduate College THE UNIVERSITY OF ARIZONA 1979 STATEMENT BY AUTHOR This thesis has been submitted in partial fulfillment of re­ quirements for an advanced degree at The University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library. Brief quotations from this thesis are allowable without special permission, provided that accurate acknowledgment of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his judg­ ment the proposed use of the material is in the interests of scholar­ ship. In all other instances, however, permission must be obtained from the author. SIGNED: APPROVAL BY THESIS DIRECTOR This thesis has been approved on the date shown below: 7 / ? 7 ? WILBERT Dare Geosciences ACKNOWLEDGMENTS My foremost acknowledgments and deepest gratitude go to my parents, Dr. and Mrs. Andrew Freiberg, for their unfailing support, both financial and moral, which made this thesis possible. - I would like to thank Dr. John Guilbert, my major advisor, for introducing me to the problems of the Boleo district and for his assis­ tance and helpful criticism. I am also grateful to Dr. Richard Beane and Dr. Arend Meijer for helpful suggestions and many useful consulta­ tions. It was upon the advice of Dr. Beane that my study of the Boleo district focused upon the Lucifer deposit. The Compahla Minera de Santa Rosalia was extremely helpful and cooperative during my visits to Santa Rosalia, providing me with, among other things, maps, an assistant, lodging and, more than once, help with my truck. I am especially grateful to Ing. Pedro Ortiz. Use of the scanning electron microprobe quantometer was made possible through the kindness of Dr. Michael Drake and the Department of Lunar and Planetary Sciences of The University of Arizona. Tom Teska provided much valuable assistance in its use. I owe special thanks to Hort Newsom for the many long and tedious hours spent showing me how to use the microprobe. Among the many students of the Department of Geosciences of The University of .Arizona who have helped me out during the course of this project, I would especially like to thank Fleet Koutz, Bob Brakenridge, iii iv Rick Gottschalk, and Greg McNew for valuable suggestions and for reading early drafts of the manuscript. TABLE OF CONTENTS Page LIST OF ILLUSTRATIONS.......... vii LIST OF T A B L E S ............................................... x A B S T R A C T ................................. - ................ xi INTRODUCTION................................................. 1 Location, Production, and Access ......................... ' 2 Previous Studies .... ................................. 5 STRATIGRAPHIC SETTING AND PETROLOGY OF THE LUCIFER MINE REGION .................... 6 Quartz Monzonite (Cretaceous) ............................. 6 Comondd Volcanics (Middle(?) and Late Miocene) .......... 9 Boleo Formation (Early Pliocene) ......................... 19 Basal Congl o m e r a t e ................................... 20 Tuffaceous Limestone ................................. 21 Tuffs and Tuffaceous Conglomerate ..................... 23 Pliocene and Quaternary Sedimentary Units Overlying the Boleo Formation.......... 33 Tres Virgenes Volcanics (Pleistocene and Recent) ........ 34 STRUCTURAL GEOLOGY ........................................... 37 General Structural Features of the Santa Rosalia (Boleo) Region ....................................... 37 Structural Features of the Lucifer M i n e .................. 38 MANGANESE D E P O S I T S ................ 46 General Features of the Lucifer Manganese Deposit ......... 46 Mineralogy of the Lucifer Deposit ......................... 56 General Considerations ............................... 56 Composition of the Cryptomelane M i n e r a l s ............ 68 Paragenetic Relationships in the Lucifer Manganese O r e ..................................... 75 ALTERATION IN THE LUCIFER A R E A ............................... 78 Alteration of Mafic Silicates ....... ........ ... 78 Alteration Associated with Manganese Mineralization .... 83 v vi TABLE OF CONTENTS— Continued Page Whole-rock Compositional Analyses of Fresh and Altered R o c k s .................. 84 D I S C U S S I O N ....................................................... 94 ORIGIN OF THE LUCIFER DEPOSIT.................................... 102 Geologic Criteria ....................................... 102 Tectonic Setting and Related Processes of Ore D e p o s i t i o n ................................. 112 Geochemical Processes of Formation ..................... 118 RELATION OF THE LUCIFER DEPOSIT TO COPPER DEPOSITS AND OTHER MANGANESE MINERALIZATION IN AND NEAR THE SANTA ROSALIA (B0LE0) DISTRICT .............................. 134 APPENDIX I: GENERAL MICROPROBE INFORMATION .............. 142 APPENDIX II: MICROPROBE ANALYSES (WEIGHT PERCENT) OF LUCIFER ORE SAMPLES............................. 145 APPENDIX III: MOLECULAR PROPORTIONS OF CRYPTOMELANE "A"-SITE CATIONS AT 8 (Mn + Fe + Al) ........ 159 APPENDIX IV: " LOCATIONS OF SAMPLES DISCUSSED IN TEXT ..... 162 LIST OF REFERENCES ............................................... 163 LIST OF ILLUSTRATIONS Figure Page 1. Location Map of Area Studied........................... 3 2. Northern Portion of the Boleo District ................. 4 3. Correlation of Lucifer and Boleo Stratigraphic Sections ..... ............ 7 4. Geologic Map of the Lucifer Mine and Surrounding Area, Baja California, M e x i c o .............. .. ..In pocket 5. Geologic Cross Section of the Lucifer Area along Line A - A * ................................... 8 6. Boleo Basal Conglomerate Overlying Comondti Agglomerate ........ .............................. 11 7. Photomicrographs of Comondu Vitrophyric-textured Volcanic Rock (Sample LZ22) ........ ....... 14 8. Photomicrographs of Comondil Felsophyric-textured Volcanic Rock (Sample LX10) 17 9. Boleo Tuffaceous Limestone Overlying Basal Conglomerate...................... 22 10. Remnant of the Manganese Ore Manto Overlying Boleo T u f f s ....................................... 27 11. Photomicrographs of Boleo Tuff with Original, Non-intraformational Texture (Sample LP3A) .... 29 12. Photomicrograph of Boleo Tuff with Intraformational Texture (Sample LZ20B) ............................. 30 13. Quaternary Conglomerate Overlying Stratified Manganese O r e ..................................... 35 14. Exposure of Partly Buried Ridge of Comondu Volcanics . 39 15. Lucifer Mine, Looking West up Wash in the Northeast Part of the Study A r e a ............................. 40 vii viii 'LIST OF ILLUSTRATIONS— Continued Figure Page 16. Dip-histogram Rosette for Bedded Comondu Volcanic U n i t s ............ 42 17. Strike-histogram Rosettes for Fractures in the Lucifer A r e a ............................ 44 18. Lucifer Ore Sample with Distinctive Clastic A p p e a r a n c e .................................... 49 19. Detail Map of the Exposure of the Ridge of Comondu Volcanics near the Southern End of the Orebody .. 51 20. Contact of Mineralized Boleo Basal Conglomerate and ComondtS Breccia at the Exposure of the Comondu R i d g e ........................ 53 21. Mineralized Comondd Bedded Volcanics Grading into Breccia........................................ 54 22. Manganiferous Laharic Breccia ............ 54 23. Boleo Tuffaceous Conglomerate Overlying Manganese Ore . 55 24. Stratified Manganese Ore Overlying Altered Boleo Basal Conglomerate ............................. 57 25. Photomicrograph of Lucifer Ore Polished Section Illustrating the Growth of Pyrolusite Around Cryptomelane ....................................... 61 26. Photomicrograph of High-K Cryptomelane Surrounding Early C o r o n a d i t e .............................. 63 27. Photomicrograph of Botryoidal Colloform Cryptomelane . 65 28. Photomicrograph of Pisolitic Cryptomelane Broken by Siliceous Gangue ................................... 65 29. X-ray Backscatter Scanning Images of Lucifer Manganese O r e .................................. 66 30. Plot of Univalent vs. Divalent Cations in Lucifer Cryptomelane "A" Sites 71 lx LIST OF ILLUSTRATIONS— Continued Figure Page 31. Pb-K-Ba Ternary Diagram ................................. 72 32. Na-K-Ca Ternary Diagram ................................. 74 33. Paragenetic Sequence of Mineral Formation in Lucifer O r e ........................ 76 34. Photomicrograph of a Sample of the Unaltered Core of a Boulder of Comondu Volcanics in Mineralized Boleo