Alteración hidrotermal y mineralogía de las vetas Sofía-Julia-Valencia, Andacollo, Neuquén

MENDIBERRI J. ; PONS M. J. ; ARCE M.

Córdoba

Congreso; XIII Congreso de Mineralogía, Petrología Ígnea y Metamórfica, y Metalogénesis; 2019

Asociación Mineralógica Argentina, Asociación Geólógica Argentina, y COMPETRO

Sofía-Julia-Valencia (SJV) vein system is hosted in the Huaraco Formation with total resource of 22900 Oz Au Eq. The mineralized structures consist of multiple overlapped veins and veinlets: (1) scarce early quartz + molybdenite + iron poor-sphalerite ± pyrite veinlets, reopened by (2) quartz ± epidote ± biotite and chlorite + calcite + pyrite + arsenopyrite + pyrrhotite ± chalcopyrite (iron rich-sphalerite) veins, that are cut by (3) quartz bearing ± chlorite ± calcite + pyrite and arsenical-pyrite veins and (4) polymetallic veins formed by quartz + sericite ± ankerite? (chlorite), pyrite, arsenical pyrite, iron-rich sphalerite + silver rich-galena + chalcopyrite + gold (argentite, pyrrhotite) and (5) late multistage calcite veins. Quartz shows granular, comb and local tension gashes and lattice bladed textures. Four types of alterations affected the host rock: (1) patches of early potassic alteration; (2) widespread propylitic alteration, (3) phyllic alteration, and (4) late supergene alteration. Based on gangue and ore mineralogy, this vein system registered an early hydrothermal stage with relatively high oxygen fugacity, a second mesothermal stage dominated by alkaline fluids (>350°C) overlapped by a later epithermal stage (main base metals and gold mineralization) formed by fluid of lower temperatures (<250°C) and lower sulfur and oxygen fugacity.