EL DEPÓSITO DE Cu-Mo-Au AGUA RICA, CATAMARCA:

MARTA FRANCHINI, AGNES IMPICCINI, ISIDORO B. SCHALAMUK, JAVIER RÍOS Y MARIA SOL O´LEARY

La Plata

Congreso; 16° Congreso Geológico Argentino; 2005

Comité Ejecutivo, Asociación Geológica Argentina

ABSTRACT Hydrothermal alteration and mineralization in a central cross section of the Agua Rica deposit have been studied in detail. Early types of  alteration and mineralization are related with the Seca Norte and Trampeadero porphyritic intrusions. Patches of potassic alteration with biotite and quartz stockwork veins are preserved in the western sector, within the widespread phyllic envelope with white mica + clay minerals (illite + dickite + smectite). Sulfides veinlets and disseminations cut early quartz veins and run parallel to the vein centers and walls. Sulfides (pyrite > chalcopyrite > molybdenite; supergene covellite > digenite) are in equilibrium with phyllic assemblages, but out of equilibrium with biotite in the potassic patches. The second event produced advanced argillic alteration and brecciation of altered lithologies. Several stages have been recognized: (1) an early and deep pyrophyllite ± pyrite ± covellite ± diaspore  (alunite?) alteration in the  altered porphyry that grades into the eastern sector to pyrophyllite ± pyrite  assemblage, in the  altered metasediment; (2) a second stage of  pyrophyllite + diaspore  veins without sulfides preserved only locally, cutting (1), (3) brecciation and precipitation of  alunite + pyrite + covellite + sulfur + zunyite cement in heterolithic and monolithic breccias and filling voids, and (4) sphalerite veinlets cutting and replacing hydrothermal cement in the uppermost levels of the heterolithic breccia.   Key words: potassic, phyllic, advanced argillic, high sulfidation, Agua Rica deposit