Some geologic and exploration characteristics of porphyry copper deposits in a volcanic environment, Sonora, Mexico Item Type text; Thesis-Reproduction (electronic); maps Authors Solano Rico, Baltazar, 1946- 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 30/09/2021 03:12:43 Link to Item http://hdl.handle.net/10150/566651 SOME GEOLOGIC AND EXPLORATION CHARACTERISTICS OF PORPHYRY COPPER DEPOSITS IN A VOLCANIC ENVIRONMENT, SONORA, MEXICO by Baltazar Solano Rico A Thesis Submitted to the Faculty of the DEPARTMENT OF MINING AND GEOLOGICAL ENGINEERING In Partial Fulfillment of the Requirements For the Degree of MASTER OF SCIENCE WITH A MAJOR IN GEOLOGICAL ENGINEERING In the Graduate College THE UNIVERSITY OF ARIZONA 19 7 5 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: /CW 7 , / f WILLIAM C . PETERS Date Professor of Mining and Geological Engineering To Amalia iii ACKNOWLEDGMENTS The author is indebted to Minera Tri6n, S.A. de C.V., Hermo- sillo, Sonora, and its staff for help and encouragement as well as finan­ cial support. Especially mentioned are Ings. Alberto J. Terrones and Rigoberto Reynoso. The Government of Mexico through the Consejo Nacional de Ciencia y Tecnologia provided payment of fees and a monthly stipend. The author acknowledges Dr. William C. Peters, professor and kind person, whose patience and guidance are high appreciated, and Drs. Spencer R. Titley and DeVerle P. Harris, members of his thesis com m ittee. The following persons contributed with their knowledge, com­ ments, and significant data: Gustavo Calderdn, former graduate student at The University of Arizona; Russell Corn, Regional Geologist, Kerr- McGee Corporation, Tucson, Arizona; Darrel Dean, graduate student. The University of Arizona; Adelaide Gutierrez, Consulting Geologist, Hermosillo, Sonora; Amador Osoria, Manager of Exploration, Industrial Minera Mexico, S.A ., Mexico, D.F.; Luis Palafox, Senior Geologist, Compania Minera Constelacidn, Hermosillo, Sonora; Claude Rangin, Research Geologist, Institute de Geologia, and professor at the Univer- sidad de Sonora, Hermosillo, Sonora; and Ariel Echavarri P ., professor at the Universidad de Sonora. iv TABLE OF CONTENTS Page LIST OF ILLUSTRATIONS........................................................................................ v ii LIST OF TABLES...........................................................................................................v iii ABSTRACT................................................................................................................... ix 1 . INTR O D U C TIO N ...................................................................................................... 1 2 . REGIONAL GEOLOGY OF S O N O R A ................................................................. 3 Pre Cam brian...................................................................................................... 3 P a l e o z o i c ......................................................................................................... 4 M e s o z o i c ......................................................................................................... 5 T ria ssic-L o w er J u r a s s ic ................................................................. 5 C r e t a c e o u s ............................................................................................ 6 C e n o z o ic ............................................................................................................ 7 T ertiary...................................................................................................... 7 Structural G e o lo g y ........................................................................................ 8 P a leo g eo g ra p h y ............................................................................................... 11 3 . RELATIONSHIP BETWEEN VOLCANIC ROCKS AND PORPHYRY COPPER D E P O SIT S..................................................... 17 Distribution of Volcanic Rocks ....................... 17 Porphyry Copper Type Occurrences ................................................... 29 4 . SOME CHARACTERISTICS OF PORPHYRY TYPE OCCURRENCES IN VOLCANIC HOST RO C K S ............................................31 Porphyry Occurrences in Sonora .............................................................. 34 Petrography and Alteration ................................ 34 M ineralization ......................................................................................... 42 S tru ctu re................................................................ 43 G e o c h e m istr y ..........................................................' ............................47 C a p p in g ................................................................................................... 50 5 . SPECIFIC FACTORS AFFECTING EXPLORATION...................................... 52 T e c t o n i c s ......................................................................................................... 52 Middle Tertiary Volcanic C over .......................... 53 Structural G e o lo g y ......................................................................................... 55 Outcrop Characteristics and Photogeology .................................. 55 v v i TABLE OF CONTENTS— Continued Page W eathering and C lim a t e ...............................................................................56 G eoch em ical E xp loration ............................................................................... 57 M in e r a liz a tio n ................................................................................................... 59 Petrography and Alteration ....................................................................... 59 G e o p h y s ic s .......................................................................... 60 6. METALLOGENIC CONSIDERATIONS....................... 62 7 . CO NCLUSIO NS............................................................................. 73 SELECTED BIBLIOGRAPHY 78 LIST OF ILLUSTRATIONS Figure Page 1. Geologic map of Sonora, M exico ............................................ in p ock et 2. Structural m ap ........................... 9 3. Precambrian paleogeography ................................. 12 4 . P a le o z o ic p aleogeograp h y and P a leo z o ic iso p a ch m a p ...................14 5. Late Triassic-Early Jurassic paleogeography .......................................15 6. Early Cretaceous paleogeography, showing reported s e c t io n s ............................................................................................................. 16 7. Distribution of Laramide and Cretaceous volcanism ......................18 8. Laramide and Cretaceous volcanic localities .................................. 19 9. Cretaceous and lower Tertiary volcanic rocks in S on ora, M e x ic o ................................................................................................ 20 1 0 . L ocation o f reported p r o s p e c t s ..................................................................... 30 11. Distribution of Tertiary postmineral volcanic cover ......................... 54 12. Interpreted distribution of magmatic activity along M ex ic o 's north w est c o a s t .................................................................... 67 13. Sillitoe's idealized model of a porphyry copper deposit .... 69 14. Diagrammatic sketch of a vertical cross section at El Alacrctn, Sonora ................................. 71 ... LIST OF TABLES Table Page 1. Some characteristics of porphyry occurrences in S o n o r a .................................................................................................................... 35 2 . Rock g eo ch em ica l v a l u e s .............................................................. 48 v iii ABSTRACT A review of the geology, including a brief description of the structural geology and paleogeography of Sonora, Mexico is presented. Basement rocks cropping out are mainly older PreCambrian metamorphic rocks and younger Pre Cambrian sedimentary rocks. A north-south trough formed during Paleozoic time is now characterized by quartzites and limestones and Triassic-Jurassic marine and terrigenous sedimentary rocks. Intense volcanic activity occurred during Cretaceous and Tertiary tim e . The Lower Cretaceous and Laramide volcanic rocks are de­ scribed, and their possible relationship with some porphyry copper