Depósitos de greisen asociados a granitos carboníferos post-orogénicos con potencial mineralizados, Siera de Fiambalá, Catamarca, Argentina

Abstract

La sierra de Fiambalá está ubicada en el centro-sur de Catamarca, sierras Pampeanas Occidentales, Argentina. Está constituída por metamorfitas precámbricas, un intrusivo granítico cámbrico, rocas básicas y ultrabásicas y granitos carboníferos epizonales (Los Ratones, El Salto y Ayacucho). Los granitos carboníferos son subalcalinas,moderadamente peraluminosos, tienen alta sílice (excepto la facies porfírica de Los Ratones) y moderadamente enriquecidos en K. Los contenidos de elementos trazas de REE indican que los granitos El salto y Ayacucho y la facies granular de Los Ratones tienen características de granitos evolucionados y diferenciados con sistemas hidrotermales. Las variaciones de elementos trazas Sn, W, Rb, U, Ba, Zr y Sr sugieren que tienen potencial mineralización.Relacionados se encuentran depósitos de greisen de Sn, W y U y metales base subordinados. Los procesos hidrotermales involucran dos estadios de alteración con metasomatismo alcalino y seguido por greisenización.

The Fiambalá range is located in the central – south part of the province of Catamarca, Western Sierras Pampeanas, Argentina. It is largely conformed by Precambrian metamorphic rocks, a Cambrian granitic intrusive, Ordovician basic and ultrabasic rocks and epizonal Carboniferous granites (Los Ratones, El Salto and Ayacucho Granites). The Carboniferous granites are subalkaline, weakly peraluminous, high silica (except for the porphyritic facies of Los Ratones granite) and moderately enriched in K. Contents of trace elements and REE indicate that El Salto and Ayacucho granites and the granular facies of Los Ratones granite have characteristics of evolved and differentiated granite associated with hydrothermal systems. The variations of trace elements, particularly Sn, W, U, Rb, Ba, Zr and Sr suggest that they correspond to granites with mineralization potential. Genetically linked to these granites there are Sn, W, U and minor base metals greisen deposits. The hydrothermal process that yield to these deposits involved two main alteration stages, beginning with alkali metasomatism follow by greissenization. According to the isotopic ages the hydrothermal processes postdate about 1 Ma the magmatic activity. The analyses of the granites and the associated greisen deposits confirm that the post – orogenic carboniferous magmatism is the major metallogenetic control of the ore deposits from the studied area. This metallogenetic control could be a usefull tool in prospecting similar deposits in the rest of the Western Sierras Pampeanas.