Paragénesis de la mineralización metálica del sistema de vetas y diseminado del área minera “El Corazón”, cantón Cotacachi, provincia de Imbabura

Abstract

“El Corazón” mining area is located in the North of the Western Cordillera, approximately 60 km to the NNW of Quito. This area is composed of a vein system and Disseminated with metallic mineralization, within Eocene volcanic rocks belonging to Tortugo Unit. The auriferous zones are in the NNE-SSW structures subparallel to Toachi Fault and in extensional secondary structures, NNW-SSE and NW-SE. Projections of these faults towards the Disseminated, evidence intersection in this area, which generates fracturing, therefore, a favorable scenario for the disseminated gold deposition. Gold mineralization is associated with zones of silicification and quartz veins generated in a transitional environment of slightly acidic in the Disseminated and neutral pH in the veins. Based on the presence of chalcedony, adularia, tetrahedrite-tennantite, dickite, high crystalized kaolinite and illite of paragonitic to phengitic composition; “El Corazón” deposit is classified as intermediate to low sulphidation epithermal transitional type. The paragenetic associations identified indicate five phases of mineralization, being II and III the phases in which the gold precipitated with sizes <10 um. Phase I: adularia, quartz, pyrite, sphalerite and chalcopyrite. Phase II: quartz, adularia, tetrahedrite, tennantite, chalcopyrite, pyrite, chalcedony, gold and galena. Phase III: chalcedony, adularia, quartz, gold and sphalerite, galena and chalcopyrite filling cavities and fractures of phase II. Phase IV: quartz, calcite, pyrite, sphalerite and galena. Phase V: transformation of feldspars to clays, filling of cavities and fractures with carbonates and quartz, formation of supernatant minerals and oxidation of primary sulfides.