The Mariana-San Marcos vein system: shallow featur of epithermal Au-Ag deposits, Cerro Negro District, Deseado Massif, Argentina. The Mariana-San Marcos vein system: shallow features of epithermal Au-Ag deposits, Cerro Negro District, Deseado Massif

PERMUY VIDAL, CONRADO; GUIDO, DIEGO; JOVIC, SEBASTIÁN; BROWN, GASSAWAY

Mineral deposit research for a high-tech world

The Society for Geology Applied to Mineral Deposits and Geological Survey of Sweden

Lugar: UPSALA; Año: 2013; p. 1303 - 1306

he Mariana-San Marcos vein system is located in the Cerro Negro project, Deseado Massif province, Patagonia Argentina. Mineralization is characterized by low sulfidation type epithermal Au-Ag quartz veins with exceptional widths and length. During the last years, Au-Ag reserves have grown significantly at Cerro Negro to proven and probable reserves of 5.74 Moz Au, 49.36 Moz Ag at the end of 2012. Epithermal veins are hosted by Late Jurassic volcanic and/or intrusive rocks of andesitic to rhyodacitic composition, grouped in the Bahia Laura Complex. Cerro Negro epithermal veins are composed of eight mineralization stages grouped in 3 episodes with quartz-adularia crustiform-colloform banding textures and minor breccias. The highest Au-Ag grades are related to the early stages in clay-rich bands and/or in late tectonic-hydrothermal breccias. This system shows several diagnostic features of a shallow epithermal environment. These features may be grouped into textural (crustiform-colloform bandings and sulfide-rich ?ginguro bands?); mineralogical (zeolites and truscottite), and geological (hydrothermal eruption breccia and hot spring deposits) features, comparable with other epithermal vein deposits such as Hishikari (Japan); Waihi, Golden Cross and Favona (New Zealand) and to active geothermal systems such as Yellowstone (USA) and Coromandel and Taupo Volcanic Zone (New Zealand). These shallow features related to high grade veins, should be considered in further exploration in the Deseado Massif metallogenial province.