Boletín de la Sociedad Geológica Mexicana Volumen 67, núm. 1, 2015, p. 119-122 http://dx.doi.org/10.18268/BSGM2015v67n1a10

Short Note

Geochronology of Mexican mineral deposits. I: the San Martín polymetallic skarn, Zacatecas

Antoni Camprubí^1,*, Eduardo González-Partida², Victor A. Valencia³, Fernando Barra⁴

¹ Instituto de Geología, Universidad Nacional Autónoma de México. Ciudad Universitaria, 04510 México, D.F., Mexico.
²Centro de Geociencias, Universidad Nacional Autónoma de México. Boulevard Juriquilla 3001, 76230 Querétaro, Qro., Mexico.
³ School of the Environment, Washington State University. Pullman, WA 99164-2812, U.S.A.
⁴ Departamento de Geología, Universidad de Chile. Plaza Ercilla #803, Casilla 13518 Correo 21, Santiago, Chile.

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

The Zn-Pb-Cu(-Ag±Au) San Martín deposit in northwestern Zacatecas is one of the most economically important and biggest skarns in Mexico. Mineral associations in this deposit belong to the sulfide skarn type (with rather “classical” prograde and retrograde zones) and contain peripheral subepithermal to epithermal veins. Re-Os ages were obtained for two molybdenite samples from deep Cu-Zn-Pb±Mo±Bi±Ag retrograde mineralization in these deposits, of 43.7 ± 0.3 and 44.0 ± 0.2 Ma, which correspond essentially to the same age. These are 1 to 3 Myr younger than preexisting K-Ar ages for the granitic stock that generated these mineral deposits. Prograde mineral associations are hereby interpreted to have been directly associated with this intrusion. Therefore, we may calculate a simple decrease rate in temperatures of hydrothermal fluids between ~100º and > 300 ºC per million years from prograde to retrograde skarn associations. Subepithermal and epithermal veins, however, remain undated.

Keywords: San Martín, Zacatecas, Mexico, sulfide skarn deposits, polymetallic ores, Re-Os, molybdenite.