Metal Geochemistry from Epithermal Deposits of the Deseado Massif, Patagonia, Argentina

RUIZ, R.; GUIDO, D.

Colorado, USA

Conferencia; SEG 2006 Biennial Conference “Wealth Creation in the Mineral Industry”; 2006

Society of Economic Geologist (SEG)

This contribution shows preliminary geochemical results from the Deseado auroargentiferous province. In this first stage, a group of more than 3,000 chemical analyses of mineralized structures was processed. The data was integrated in a geographic information system (GIS), combining geology and mineralization. All the geochemical information was compiled, discriminated, and grouped by its geographic location into two main regions: the Western area (Cerro Bayo, Aragonesa, Laguna de los Cisnes, La Bajada, Cañadas, La Manchuria, Maria Esther, San Agustin, La Marciana, and Noroccidental projects) and the Oriental area (Marina, El Aguila, La Calandria, Tres hermanas-Laurel, Cerro Moro projects). Statistical parameters (average, standard deviation, correlation coefficient, etc.) were defined for each element (Au, Ag, Cu, Pb, and Zn) in both areas, as a result of the element analysis. Also, with these data, several diagrams were generated in order to define relationships between elements and groups of elements (precious and base metals). In addition, the distribution tendencies of the elements according to their geographic location were considered in the analysis. There is a positive dependence (correlation) between the element pairs: Ag-Au, Ag-Pb, Ag-Zn, and Pb-Zn for the Oriental area and Ag-Au, Cu-Pb, Cu-Zn and Pb-Zn for the Western area. The observed Ag:Au ratio is relatively higher than classic low-sulfidation epithermal systems, taking into account that the ratio ranges from 0.1 to 17.7 for the 15 worldwide epithermal deposits and is close to 10:1 for the Cerro Vanguardia mine. This situation could be related to the high proportion of Ag-rich deposits that are situated in the province (Mina Martha and Manantial Espejo are examples) and could also be an indicator of the high proportion of intermediate-sulfidation-type deposits in the province. The ratio for the intermediate-sulfidation-type deposits ranges from 1 to 1,393. The relatively higher Au and base metals concentration in the Oriental area could be related to field evidence, such as the presence of basement outcrops and the lack of hot-spring environment deposits, in order to consider a deeper level of exposure for the epithermal deposits in the east. However, the base metals total content is higher in the west, which could be associated with the fact that there are more intermediate-sulfidation-type deposits (Ag and base metals rich) in the Western area.