GUIDEBOOK SERIES Volume 40 GOLD AND BASE METAL DEPOSITS IN THE MEXICAN ALTIPLANO, STATES OF ZACATECAS AND SAN LUIS POTOSI, CENTRAL MEXICO Guidebook Prepared for the Society of Economic Geologists Field Conference—October 5-9, 2010 Field Trip Leader: Erme Enriquez SOCIETY OF ECONOMIC GEOLOGISTS Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3929156/9781934969939_frontmatter.pdf by guest on 29 September 2021 GUIDEBOOK SERIES OF THE SOCIETY OF ECONOMIC GEOLOGISTS, INC. Guidebook 40 ISBN 978-1-934969-26-7 CD-ROMS of Guidebook 40 May be purchased from Society of Economic Geologists, Inc. 7811 Shaffer Parkway Littleton, CO 80127 USA Telephone: 1.720.981.7882 Fax: 1.720.981.7874 Website: www.segweb.org E-mail: [email protected] Publication Date: September 2010 Cover: Area of central Mexico visited during this field trip. Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3929156/9781934969939_frontmatter.pdf by guest on 29 September 2021 Contents Preface………………………………………………………………….…………………….iii Acknowledgments…………………………………………………………………………....v Itinerary………………………………………………………………………………………vii Route Map……………………………………………………………………………………ix List of Participants………………………………………………………………………..….x English-Spanish Geological and Survival Terms……………………………………………xiii FIRST DAY Road Log from San Luis Potosi City to Zacatecas City, The Francisco I. Madero and the Cozamin Mines, San Luis Potosi, and Zacatecas States Erme Enriquez………………………………………………………………….……1 Geology of the Madero Ore Deposit, Zacatecas, Mexico Leopoldo González-V. and Randolfo López-Soto………………………..…………..15 Contribution to the Definition of Superimposed Metallogenic Events in the Francisco I. Madero Ore Deposit, Zacatecas, Mexico Miriam Yta and Raúl Moreno-Tovar………………………………………………...31 Technical Report, Cozamin Mine, Zacatecas, Mexico [Excerpt]…………………………....45 Gordon Doerksen, Jenna Hardy, Robert Sim, and Jeff Woods SECOND DAY Road Log from Zacatecas to Concepción del Oro District, the Peñasquito Mine, and the Camino Rojo Project, Zacatecas State Erme Enriquez……………………………………………………………………….65 Peñasquito Feasibility Study: 100,000 MTPD, NI-43-101 Technical Report [Excerpt] James S. Voorhees, Charlie Ronkos, Jerry Hanks, Tom Drielick, Tom Wythes, Conrad Huss, Michael Pegnam, and Jim Johnson………………………………….77 Technical Report Preliminary Assessment, based on Report, “Technical Assessment of Camino Rojo Project Zacatecas, Mexico” [Excerpt] J. Douglas Blanchflower, Christopher Kaye, and Howard Steidtmann…………….97 i Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3929156/9781934969939_frontmatter.pdf by guest on 29 September 2021 THIRD DAY Road Log from Zacatecas Back to San Luis Potosi and to the Cerro San Pedro Mine, Zacatecas, and San Luis Potosi States Erme Enriquez……………………………………………………………………....127 Geology of the Cerro San Pedro, Precious and Base Metals Mining District, San Luis Potosí, Mexico Mark A. Petersen……………………………………………………………………137 Mesa Central of México: Stratigraphy, Structure, and Cenozoic Tectonic Evolution Ángel Francisco Nieto-Samaniego, Susana Alicia Alaniz-Álvarez, and Antoni Camprubí (Reprinted with permission of the GSA) …………………….155 ii Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3929156/9781934969939_frontmatter.pdf by guest on 29 September 2021 Preface Mexico has been an outstanding producer of silver, along with other metals that include gold, copper, zinc, lead, wolframium, and molybdenum. The mining activity accounts for 1 to 3% of the GDP in Mexico. W ith the recent changes in the mining legislation and the Constitution Article 27, exploration companies have given special attention to exploration in Mexico. O ne state with a great amount of continuing activity is Zacatecas. The discovery of Peñasquito and the continued operation of Fresnillo will make these two the largest gold and silver mines in Latin America. San Luis State has also entered in the quest for gold-silver and base metals exploration. Old mine districts like Cerro San Pedro continue producing gold and silver—currently from bulk tonnage mining. Since the mining law changed in 1992, the national gold production has increased from 10.4 tonnes (t) in 1992 t o 68.9 t in 2009, i .e., 662% in only 12 years. G old production is expected to increase by 15% in 2010. Silver production has increased, although not as drastically, by 19% in the same period of time, from 2.317 Mt in 1992 to 2.890 Mt in 2009. The change in the mining law has, therefore, significantly affected the production of silver and gold and the exploration for both. A paper by Leopoldo Gonzalez and Randolfo Lopez clearly explains the steps leading to the discovery of the Madero deposit. A polemic origin has been assigned to the deposit, by which some experts classify it as a S EDEX and others as a skarn deposit. C omplementing the description of the Madero deposit, Miriam Yta describes the superimposed events that led to mineralization and explains the process of alteration in the different types of rocks. NI-43-101 technical reports have been provided for the description of Peñasquito and Camino Rojo. The Peñasquito feasibility study discusses the economic studies prepared by M3 Engineering & Technology Corporation (M3), summarizing the work performed on the property. This report was prepared for Minera Peñasquito, S.A. de C.V., a wholly owned subsidiary of Glamis Gold Ltd. (Glamis). The main scope was given to evaluating the economics of the plant operating at 100,000 M TPD versus the previously envisioned 50,000 MTPD. The orebody is polymetallic, with the precious metals of silver and gold providing over one-half the revenue, and the base metals of lead and zinc providing the remainder. The study sets forth conclusions and recommendations, based on M 3’s experience and professional opinion, that result from their analysis of work done and data collected. Peñasquito hosts a total of 17.8 Moz of gold. Silver iii Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3929156/9781934969939_frontmatter.pdf by guest on 29 September 2021 reserves totaled 1,070.1 Moz, and proven and probable lead and zinc reserves total 7.2 and 15.9 M lb, respectively. Annual production over the life of mine (estimated 22 years) is expected to ramp up to approximately 500,000 oz of gold, 28 Moz of silver, and over 450 M lb of zinc. The Camino Rojo gold-silver-lead-zinc occurrence is a new discovery with no evidence of prior exploration. Canplats has carried out aggressive and continuous exploration work on t he property since its discovery in July 2007. During the intervening time, this exploration work has included the following: prospecting, reconnaissance geologic mapping, test pitting with geochemical sampling, trenching with geological mapping and geochemical sampling, induced polarization surveying, and reverse circulation and diamond drilling. The 2007 t o 2008 exploration work focused on the Represa zone, where a large occurrence of gold-, silver-, lead- and zinc-bearing mineralization is hosted by highly altered, silicified and oxidized metasedimentary rocks. The Represa zone has been traced by drilling for more than 1,000 m east- west, 460 m north-south and vertically to a depth of 820 m. Drill hole intercepts (not true widths) with gold and silver values exceeding 0.25 g/t and 5 g/t, respectively, range from 52 to 728 m. Within these drilling intercepts the precious metal-bearing mineralization has good lateral and vertical continuity. Canplats was taken over by Goldcorp Inc. in 2009. The deposit hosts 3.44 Moz of gold and 60.7 Moz of silver. Finally, the description of the Cerro San Pedro, done by Mark Petersen, closes this mining safari. Cerro San Pedro, despite the difficulties of operating due to environmental issues, finally will take advantage of the high gold prices in the market. C erro San Pedro hosts proven and probable reserves estimated as approx. 1.4 Moz of gold and 52 Moz of silver as in 2009. The underground and bulk mining activity in the Mexican Altiplano (Mesa Central) is the main topic of this field trip. The Society of Economic Geologists presents this introduction to the basic geologic concepts for exploration in the Mexican Altiplano in the coming years. ERME ENRIQUEZ iv Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/3929156/9781934969939_frontmatter.pdf by guest on 29 September 2021 Acknowledgments The Society of Economic Geologists (SEG) would like to thank all the companies that have given permission to visit their properties. For Peñoles, special thanks to Ing. Armando Sanchez (Mines Director) and Randolfo Lopez (Chief of Geologists) for the tour of the Francisco I. Madero mine. To Darren Pylot (President) and Telesforo Martinez (General Manager) of Capstone Gold, thanks for the opportunity to tour the Cozamin mine. Thanks to Gold Corp., through Salvador Garcia (Vice-President Operations Mexico), Gassaway Brown, and Steve Weiss, for showing their operations at the Peñasquito mine and the Camino Rojo project. Many thanks to Mark Petersen for being the liaison between the SEG and Newgold Inc., and for the great tour of the Cerro San Pedro mine complex. Likewise, the SEG thanks the authors of the papers contained in this publication; thanks for their support in helping with the timely completion of this guidebook. Thanks to Gabriel Arredondo for helping with some of the logistics and road logs. The road logs were put together using all the published information available and tours of the mine sites by the