Abstract

PERMUY VIDAL, Conrado et al. Características metalogenéticas de Eureka West, principal clavo mineralizado de la veta Eureka, distrito Cerro Negro, Macizo del Deseado. Rev. Asoc. Geol. Argent. [online]. 2016, vol.73, n.1, pp.64-77. ISSN 0004-4822.

The Cerro Negro mining district is located in the northwestern margin of the Deseado Massif. It contains a group of epithermal Au-Ag vein deposits with estimated reserves of 6,7 Moz Au eq., being one of the most important recent epithermal discoveries in the world. It comprises some Au-Ag rich vein systems hosted in the Bahía Laura Volcanic Complex of Jurassic age. In the western part of the district, volcanic rocks are grouped into the Lower Section of intermediate composition which hosts most of Au- Ag high grade veins. Above this unit, a district scale discordance places the acidic in composition Upper Section. Eureka vein is one the of the most important mineralization in the region hosted in NW major fault of 5 Km long and reaching up to 20 meters width. Eureka West constitutes a high grade ore shoot which contains over 25% of the district resources, composed of multiple filling stages grouped into 4 main episodes. These were interpreted due to the evolution of two main hydrothermal events and a late tectonic-supergene stage. High Au-Ag mineralization took place during the first hydrothermal event related to andesitic-dacitic volcanism (157-156 Ma). Lately, the second widely distributed hydrothermal event overlaps with lower temperatures and hot spring deposits at surface, possible linked to rhyolitic volcanism. During the last event, the Eureka West ore shoot was partly eroded and covered by Jurassic post-mineral deposit. Consequently, tectonic and supergene processes led to deep oxidation and re-concentration of precious metals.

Keywords : Epithermal; Au-Ag veins; Jurassic; Patagonia.

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