A contribution to the knowledge of the mineralization at mina Capillitas, Catamarca

Abstract

The Capillitas deposit is part of the Farallón Negro Volcanic Complex, Catamarca Province, north western Argentina. The epithermal mineralization is related to the Capillitas diatreme, a volcanic pipe composed of intrusive and volcanoclastic rocks of rhyolitic todacitic composition of Miocene age which is located in the granitic basement block of the Sierra de Capillitas. The deposit consists of numerous mineralized veins which crosscut the diatreme volcanics and the adjacent Capillitas granite. The different geological environments, the alteration features and theore mineralogy enable to distinguish between highand intermediate-sulfidation environments, which are overprinted by supergene processes. The first group is accompanied by advanced argillic alteration and silicification and in the second rhodochrosite and quartz are the predominant gangue minerals. The polymetallic character of the Capillitas epithermal deposit is clearly emphasized by its complex Cu-Pb-Zn-Fe-Mn- As-Sb paragenesis, with minor W, Bi,Sn, Te, Ag and Au and traces of Ge, Cd, In, V, Ni and Tl, present in more than150 different minerals. Additionally, Capillitas represents the type locality for the two new mineral species putzite and catamarcaite. The hydrothermal vein system at Capillitas was formed under strongly changing p-T-X conditions. Cu,As, Te, Sn, Bi and Au represent the key metals of the high-sulfidation stage whereas the metal association Zn-Pb-Ag is typical for the intermediate-sulfidation stage. Based on fluid inclusion studies, the Capillitas deposit canbe characterized by temperatures of ore formation mostly below 300 °C and low salinities (< 6 wt. % NaCl equivalent).