Exploration and development at the La Negra Mine, Maconi, Queretaro, Mexico Item Type text; Thesis-Reproduction (electronic) Authors Gaytán Rueda, José Eligio, 1940- 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 02/10/2021 13:12:35 Link to Item http://hdl.handle.net/10150/554937 EXPLORATION AND DEVELOPMENT AT THE LA NEGRA MINE, MACONI, QUERETARO, MEXICO by Jos£ Eligio Gaytcin Rueda 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 1 9 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: WILLIAM C. PETERS /date Professor of Mining and Geological Engineering DEDICADO A mi esposa: Blanca Rosa A mis hijos: Jos6 Eligio Juan Rafael Javier Andres ACKNOWLEDGMENTS Various factors have enabled the writing of this thesis. The first, and without doubt the cause of the others, was the granting of a scholarship by Industrias Penoles, S.A., through Ing. Pedro Sanchez Mejorada, at present Director of the Division of New Projects and De­ velopment, who has advised me in the development of the thesis and throughout my professional career. For this, I would like to give him . special thanks. I would also like to thank Industrias Pefloles, S.A., the spon­ sor of the scholarship for one year. Penoles has authorized the incor­ poration in the thesis of all information obtained as a result of the studies conducted by me during the two years (1970-72) during which I acted as resident geologist at the La Negra mine. I am grateful to Ing. Manuel Castilldn Bracho, Subdirector of Exploration, and Ing. Gustavo Aguilar Arzate, Divisional Manager, for ■ the help received from them in the development of my present activities. Overall, I express my gratitude to the Mining Division of Penoles, directed by Ing. Carlos.Sierra Valdes, and especially to Ing. Eduardo Garcia Guerrero, General Manager, Ing. Luis Corrales Velasco and Ing. Carlos Madrazo, Divisional Managers of the Mining Division, for the help received from them during my residence at the La Negra mine. I would like to express my appreciation to the Department of Mining and Geological Engineering and to Dr. Willard C. Lacy, its chairman during the student period, and especially to Dr. William C. Peters, who advised me during my studies, and Dr. Thomas J. O'Neil and Dr. Charles E. Glass. TABLE OF CONTENTS Page LIST OF ILLUSTRATIONS . ............... viii ABSTRACT . .... .... .... .... .... .... ... • x 1. INTRODUCTION .... ... ... ... .... ... ... .. .... 1 Geographic Setting .......................... 2 Historical Information ............... 4 2 . REGIONAL tz? E (Z) l_i (2) ............o............... 6 Physiography and Geomorphology ................. 6 Lithology and Stratigraphy. ..................... 8 Sedimentary Rocks ............o. .......... 9 Las Trancas Formation .................. 9 El Doctor Formation .................... 9 Cerro Ladrdn Facies. ................ 9 El Sacavdn Facies .................. 10 San Joaquin Facies ................. 10 La Negra Facies ................... 10 Soyatal Formation ..................... 11 Mezcala Formation .................... 11 El Morro Conglomerate .................. 11 Surficial Deposits ..................... 12 Igneous Rocks .......................... 12 Structure ................................. 12 3 . GEOLOGY .....o............... .......... 14 Sedimentary Rocks.................... ....... 14 Igneous Rocks ............................. 15 Metamorphic Rocks ...............o... ....... 15 4. ORE-BODY DEVELOPMENT ......................... 21 Old Mine Workings .......................... 21 Preproduction Development Work ................. 23 Mining and Sampling Methods ............... i, .. 27 Scale of Operation and Life of the Mine ............. 32 Ore Grade and Tonnage. ....................... 34 vi vii TABLE OF CONTENTS—Continued Page 5. ECONOMIC GEOLOGY............... 37 Ore Control ............... 38 Lithologic Factors ..................... 38 Stratigraphic Factors . ............ .. ....... 39 Structural Factors ........................ 39 Chemical Factors .................................... 39 Density and Textural Factors ................. 40 Ore Mineralogy. ............... 40 Mineral Paragenesis and Zoning ............... 41 Ore Genesis . ^ . 44 6. EXPLORATION ................................. 48 Exploration Program at Depth .................... 52 Systematic Exploration at the Mine ................ 54 Results and Costs of the Exploration at Depth and at the Mine ........................... 55 Geologic Interpretation. .................... 58 Ore R eserv es ............................... ............ 59 Results of Exploration at the Mine ............. 62 Cost of Exploration at Depth and at the Mine ...... 62 Exploration in Socavdn El Alacrdn ................. 63 7. SUMMARY AND CONCLUSIONS. ..................... 66 APPENDIX A: ORE RESERVE ESTIMATE FOR LA NEGRA AND EL ALACRAN ORE BODIES, EXPLORATION PROGRAM, 1964-67. ................... 69 APPENDIX B: ORE RESERVE ESTIMATE FOR THE LOWER PART OF LA NEGRA ORE BODY FOUND DURING FIRST STAGE OF EXPLORATION PROGRAM AT DEPTH, 1972 ............................. 79 APPENDIX C: SUMMARY OF DIAMOND DRILL HOLE LOGGING. 85 REFERENCES. ................................ 97 LIST OF ILLUSTRATIONS Figure Page 1. Location of the La Negra mine, Quer^taro, Mexico . 3 2o Physiographic provinces y Estados Unidos Mexicanos ..... 7 3. Regional geology of the La Negra district ........ in pocket 4. Local geology of the La Negra area ............ in pocket 5. Geologic map of sublevel 2317 (7), plan v iew ................ 17 6. Geologic map of sublevel 2295 (3), plan view .......... 18 7. Geology and sampling maps of sublevel 2266 (Cono) ..... 19 8. Geologic map of sublevel 2170, plan view ............ 20 9. Composite map of the old mine workings of the La Negra mine ............................ 22 10. Longitudinal and cross sections of the La Negra ore body ................................. 24 11. Sublevel preparation, first stage .................. 25' 12. Sublevel preparation, second stage. ................ 26 13. Ore haulage and mining system, isometric drawing. ...... 29 14. Isometric.projection of the La Negra ore body .......... 30 15. Map.showing sampling method, diamond drill holes, and pocket of mineral at the footwall, sublevel No. 5 (elevation 2317 m) ..................... 33 16. Ore reserve estimate of the La Negra ore body. ......... 35 17. Variation of metallic contents at depth, based on average assays, IQO-m intervals ................ .43 18. Plan view showing target zone No. 1............... 49 viii ix LIST OF ILLUSTRATIONS--Continued Figure Page 19. Cross section of the La Negra ore body exploration program between elevation 2,000 and 2,100 m ........ 50 20. Generalized geologic map along Socavdn La Negra and El Alacrcin ................................................... 51 21. Plan view showing the mineralized zones intersected with the horizontal diamond drill holes between elevation 2,000 and 2,100 m .................. 56 22 . Cross section of the La Negra ore bodies I and II....... 57 23. Longitudinal projection of the La Negra ore body II, ore reserve estimate map ..................... 60 24. Longitudinal projection of small pocket of mineralization at the footwall of the La Negra ore body II, ore reserve estimate map ........................ 61 ABSTRACT The La Negra mine, located in the central part of the Mexican Republic, belongs to the Lower Range subprovince of the Sierra Madre Oriental province. - The La Negra ore body is an epigenetic and typically metasomatic or pyrom eta somatic deposit where the mineralization is present as massive sulfides, with silver as hessite, lead as galena, copper as chalcopyrite, and zinc as marmatite. The exploitation method is a combination of sublevel and long hole blasting. The initial ore reserves have been estimated at 1,368,427 metric tons, averaging 254 g/metric ton Ag, 1.4% Pb, 1.52% Cu, and 3.3% Zn. The life of the mine was estimated to be about 12 years at the production rate of 120,000 metric tons per year. Actually, this pro­ duction has been increased to 156,000 metric tons per year and the life of the mine is still considered to be 12 years because the ore reserves have also been increased by 30 percent since the continuation of the ore body at depth has been located.