Boletín de la Sociedad Geológica Mexicana

Volumen 67, núm. 2, 2015, p.349-355

Short Note

Geochronology of Mexican mineral deposits. II: Veta Madre and Sierra epithermal vein systems, Guanajuato district

Juan José Martínez-Reyes1,2, Antoni Camprubí3,*, I. Tonguç Uysal4, Alexander Iriondo5, Eduardo González-Partida5

 

1 Departamento de Ingeniería en Minas, Metalurgia y Geología, Universidad de Guanajuato. Ex-Hacienda de San Matías s/n, Fracc. San Javier, 36025 Guanajuato, Gto., Mexico.
2 Programa de Posgrado en Ciencias de la Tierra, Universidad Nacional Autónoma de México. Blvd. Juriquilla 3001, 76230 Querétaro, Qro., Mexico.
3 Instituto de Geología, Universidad Nacional Autónoma de México. Ciudad Universitaria, 04510 México, D.F., Mexico.
4 Geothermal Energy Centre of Excellence, University of Queensland. Brisbane St Lucia, QLD 4072, Australia.
5 Centro de Geociencias, Universidad Nacional Autónoma de México. Boulevard Juriquilla 3001, 76230 Querétaro, Qro., Mexico.

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Abstract

This paper presents two new high-resolution geochronological determinations for the epithermal deposits in the World-class Guanajuato mining district, in central Mexico. These are a Rb-Sr isochron age in illite at 28.47 ± 0.55 Ma for the Villalpando and San Juan de Dios low sulfidation veins of the Sierra group of veins, and a 40Ar/39Ar plateau age in adularia (“valencianite”) at 30.20 ± 0.17 Ma for the La Valenciana ore shoot of the famous Veta Madre intermediate sulfidation vein. These determinations have greater accuracy, precision and trueness than the preexisting K-Ar determinations for similar adularia samples. The accuracy of such determinations supports the idea of a diachronic emplacement of intermediate and low sulfidation deposits in this district, the former being older than the latter, similar to other epithermal deposits in Mexico. Also, the ~2 m.yr. span between the Veta Madre and Sierra groups of epithermal veins is in agreement with other case studies, regardless of the size of the deposit.

Keywords: Guanajuato, Mexico, epithermal deposits, intermediate sulfidation, low sulfidation, Rb-Sr ages, illite, Ar/Ar ages, adularia.


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