Geology and mineralogy of the Santo Nino Ag-Pb-Zn vein, Fresnillo District, Mexico
The Santo Nino Ag-Pb-Zn vein is the major producer of the Fresnillo District, located 750 km NW of Mexico City. It is over 2.4 km long, more than 480 m in vertical extent, more than 2.5 m wide overall, and has average grades of >600 gm/t Ag and <2% combined Pb and Zn. The vein is hosted by a tilted sequence of Cretaceous graywackes, shales and andesitic volcanics and extends upward into a Lower Tertiary conglomerate. Up to 5 separate opening events occurred along the vein, resulting in discontinuous stages of brecciation and crustiform banding. Ore mineral zonation is well developed both vertically and laterally and closely reflects metal and metal ratio distributions. Ore minerals are sphalerite, galena, pyrite, chalcopyrite, arsenopyrite, marcasite, pyrrhotite, acanthite, native silver, and three coexisting solid solution series, pyrargyrite-proustite, polybasite-arsenopolybasite, and tetrahedrite-tennantite in a gangue of quartz, calcite, clay, sericite,and chlorite. A 5-stage paragenetic sequence can be established: 1) pyrite, arsenopyrite, quartz, 2) sphalerite, galena, chalcopyrite, quartz, 3) tetrahedrite, pyrargyrite, polybasite, quartz, 4) acanthite, native silver, calcite, quartz, and 5) calcite. Preliminary microprobe analyses indicate that the Ag-rich solid solution series are Sb-rich in the central and upper portions of the vein and As-rich at deeper levels.
- Research Organization:
- Dartmouth College, Hanover, NH (USA)
- OSTI ID:
- 6596801
- Report Number(s):
- CONF-8510489-
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Vol. 17; ISSN GAAPB
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
580300* -- Mineralogy
Petrology
& Rock Mechanics-- (-1989)
CHALCOGENIDES
CHALCOPYRITE
COPPER COMPOUNDS
COPPER SULFIDES
CRETACEOUS PERIOD
DEVELOPING COUNTRIES
GALENA
GEOLOGIC AGES
GEOLOGIC HISTORY
GRAYWACKE
IRON COMPOUNDS
IRON SULFIDES
LATIN AMERICA
LEAD COMPOUNDS
LEAD ORES
LEAD SULFIDES
MARCASITE
MESOZOIC ERA
MEXICO
MINERALIZATION
MINERALOGY
MINERALS
NORTH AMERICA
ORES
PETROGENESIS
PYRITE
ROCKS
SANDSTONES
SEDIMENTARY ROCKS
SHALES
SILVER ORES
SULFIDE MINERALS
SULFIDES
SULFUR COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
ZINC ORES