Mineralización de Cu (V-U) en la formación Huincul, prospecto Tordillos, cuenca Neuquina

Abstract

Tordillos is one of several stratiform copper deposits (V, U) of the Neuquén Basin, located in the northern sector of the Dorsal Huincul to the SW of anticlinal Sauzal Bonito. The deposit has an estimated total resource of 9.5 Mt and 0.42 % Cu grades with U (135-251 ppm) and V (250-980 ppm) anomalies. The mineralization is epigenetic and fills the secondary porosity of the permeable and bleached sandstones of the Huincul Formation. It consists of chalcocite with relict chalcopyrite and bornite and supergene Cu-V-U minerals (covellite, brochantite > malachite, copper wad-tenorite and cuprite, chrysocolla, Cu-KBa vanadates and urovanadates) always in contact with impregnations of bitumen. The textural evidences of dissolution of authigenic minerals (hematite-quartz-barite 1-calcite 1) and detrital grains and the chronological order of precipitation of new cements (clays-barite 2-pyrite-calcite 2-Cu sulfides-barite 3) in sandstones document a complex history for the formation of this deposit. The influx of several pulses of fluids (basinal waters rich in Ba, hydrocarbons, and brines with Cu chlorides) and their mixing with interstitial waters of the Huincul Formation, that contained sulfates, may have produced the mineralization. The Andean tectonics during the Miocene must have caused the breakdown of seals and the upward flow of these multiple fluids pulses from the reservoir into the sandstones and conglomerates of the Huincul Formation through preexisting structures of the Dorsal de Huincul.