Geology and mineral deposits of the San Cristobal district, Villa Martin Province, Potosi, Bolivia

Abstract

The San Cristobal silver district near Uyuni, Bolivia, was jointly studied in detail during the months of August to November 1966 by members of the Servicio Geologico de Bolivia and the U.S. Geological Survey, under the auspices of the Agency for International Development, U.S. Department of State. The rocks of the district are Cenozoic. The oldest rocks are the red beds of the Potoco Formation, which are unconformably overlain by agglomerate, conglomerate, sandstone, and tuff of the flat-lying Quehua Formation. Both formations are intruded by dacite porphyry and andesite porphyry stocks, and both are overlain by recent dacite porphyry lava flows. The intrusive and sedimentary rocks near the intrusive contacts are hydrothermally altered. Mineral deposits of the district ai*e associated with the intrusive rocks and are of four distinct types: 1. Sulfide veins containing lead, zinc, and silver associated with dacite porphyry intrusives (Colon and Tesorera mines). 2. Oxide veins containing iron and silver associated with andesite porphyry intrusives (Toldos mine). 3. Partial sulfide replacement of intrusive breccia containing silver, lead, and zinc (Animas mine). 4. Disseminated lead-zinc-silver minerals in altered dacite porphyi*y intrusives and in adjacent altered sedimentary rocks (Hedionda mine). Disseminated silver minerals may provide a basis for the development of open-pit silver mines. This possibility should be further investigated, beginning with geochemical surveys and hydrothermal alteration studies.

Volcanic stratigraphy, structural controls, and mineralization in the san cristobal Ag–Zn–Pb deposit, southern bolivia

“…The first widely available study was by Jacobson et al (1969), who interpreted the district as the roots of a deeply eroded stratovolcano. While sampling to provide grade and to image estimates during a brief reconnaissance study, Jacobson et al (1969) prepared a 1:8,000 scale geologic outcrop map and noted the occurrence of alunite, kaolinite, and montmorillonite.…”

“…The first widely available study was by Jacobson et al (1969), who interpreted the district as the roots of a deeply eroded stratovolcano. While sampling to provide grade and to image estimates during a brief reconnaissance study, Jacobson et al (1969) prepared a 1:8,000 scale geologic outcrop map and noted the occurrence of alunite, kaolinite, and montmorillonite. During a brief reconnaissance visit, Richter et al (1992a) provide additional ore grade information and collected two samples of volcanic rock from flow domes, which yielded K/Ar dates of 8.5^0.3 Ma to 8.0^0.1 Ma for biotite.…”

Improved process development for complex silver ores through systematic, advanced mineral characterisation

“…Other sites are Tesorera, Trapiche, Bertha, Colon and Animas mines. Jacobson et al, 1969;Long et al, 1991 andKamenov et al, 2002) Toldos ore is located at an elevation of 4100 m and is 2 km away from San Cristobal. Toldos is an old pit which has been geologically described by as forming at "high temperatures with the formation of large quantities of crystalline specular hematite with glassy quartz" and Jacobson et al, 1969 as "oxide veins containing iron and silver associated with andesite porphyry intrusive".…”

“…Jacobson et al, 1969;Long et al, 1991 andKamenov et al, 2002) Toldos ore is located at an elevation of 4100 m and is 2 km away from San Cristobal. Toldos is an old pit which has been geologically described by as forming at "high temperatures with the formation of large quantities of crystalline specular hematite with glassy quartz" and Jacobson et al, 1969 as "oxide veins containing iron and silver associated with andesite porphyry intrusive". The ore mineralogy is complex; some of the minerals present include arsenopyrite, barite, pyrite, quartz, native silver, stromeyerite, galena, sphalerite, tetrahedrite, chalcopyrite, pyrargyrite and polybasite.…”

“…MSC is a subsidiary of Sumitomo Corporation, Japan, and is the 3 rd largest silver mine and 5 th largest zinc mine worldwide (Duran and Block, 2012). Jacobson et al, 1969) MSC comprises a number of different sites, according to Jacobson et al, (1969); the first mine operated was the Hedionda Mine at Jayula reported by a Spanish priest, Barba, in 1637, however repeated attempts to mine silver failed because of the presence of carbon dioxide (CO 2 ) gas which caused the death of many miners. After that, a Polish engineer Josef Jackowski operated the Hedionda Mine at Jayula from 1896-1901 and 1927-1936, resolving the problem of CO 2 .…”