Germanium associated with epithermal mineralization: examples from Bolivia and Argentina

摘要

Germanium is enriched in several epithermal deposits of Bolivia and Argentina. PbZn-Ag deposits of the Bolivian silver-tin belt may contain high-grade Ge mineralization. Ge is present as the mineral argyrodite, Ag8GeS6, which is usually associated with a bonanza-grade silver mineralization composed of Ag- sulfosalts (pyrargyrite, stephanite, polybasite, diaphorite),native silver and acanthite. A significant anomaly of Ge was detected in Ag-enriched ore shoots of the Porco deposit. Ge also occurs in polymetallic and precious metal-bearing ore at Capillitas, Argentina.Ge is either bound to the mineral argyrodite, thus similar to the deposits in Bolivia, or present in supergene enriched copper ore of the La Rosario vein. The latter paragenesis is characterized by distinct Ge minerals such as putzite, catamarcaite,"Ge-stannoidite' (all of them represent new mineral species) and briartite which are associated with high-grade chalcocite-bornite ore. The Ge mineralization of Bolivia and Argentina was generated in an epithermal environment of either low-sulphidation (Ag-Zn-Pb) or high-sulphidation (Cu-As-Au-W) type.