Angélica copper deposit: Exotic type mineralization in the tocopilla plutonic complex of the Coastal Cordillera, Northern Chile

Abstract

The Angélica copper deposit is situated at the southernmost sector of the Jurassic Tocopilla plutonic complex in the North Chilean Coastal Cordillera. This deposit occurs in monzonitic to monzodioritic rocks, and has platelike orebodies with no appreciable hydrothermal alteration nor sulfide mineralization. The mineralized zones are located in the western side of the two main normal faults with NE and NW orientations, and are characterized principally by impregnation of supergene copper products of atacamite and minor amounts of chrysocolla, lavendulan and "black copper". Generally, chrysocolla is more abundant at a distal NE sector of the deposit. The black copper is Cu-Fe-Mn-Si-Cl-rich multimineral aggregates composed of atacamite with minor amounts of quartz, pseudomalachite, dioptase, neotocite, gypsum, paratacamite and melanothallite, and its surface exhibits nanometer-sized cylindrical morphologies. All these characteristics suggest an exotic origin for the Angélica copper deposit. A few vein-type copper deposits situated at the southwestern sector along the NE-oriented fault are inferred as the possible source of the Angélica copper deposit. © 2007 The Authors Journal compilation.