Gold and trace-element content in epithermal sulfides from the Agua Rica deposit, Catamarca, Argentina

FRANCHINI MARTA; DAVE LENTZ; LUO YAN; LAURA MAYDAGÁN

Upsala

Congreso; 12th SGA Biennial Meeting; 2013

SGU, Geological Survey of Sweden

Agua Rica is a world class Cu-Au-Mo deposit located in Catamarca, Argentina. In this deposit, the polymetallic epithermal alteration-mineralization stages are superimposed upon older porphyry Cu-Mo mineral assemblages. Laser ablation inductively coupled plasma-mass spectrometry (LA ICP-MS) analysis of sulfides at Agua Rica revealed ?invisible? Au content in pyrite and marcasite in the upper levels of the hydrothermal matrix-supported hydrothermal breccia. The ore pyrite occurs as either very fine, irregularly shaped grains in late veinlets, or in colloform rims on earlier gold-free and Co-Mo rich pyrite cores. In the pyrite rims Ag, Pb, Bi, Cu, and Zn have a behavior comparable with that of Au; As does not correlate with Au. The very fine-grained pyrite crystals from the veinlet have the highest Au content (up to 12.9 ppm) of all analysed pyrite crystals. It is possible that these greigite-like precipitation stages reflects rapid boiling events in an open space filled with hydrothermal solutions supplied by continued fluid pathways generated by brecciation. The study has also demonstrated the presence of Au and other trace elements in other sulfides and enargite at Agua Rica. Laser spot analysis in combination with the element-distribution images show the heterogeneous distribution of the trace elements in pyrite, their associations, and the presence and distribution of nuggets