General geology of La Coipa precious metal deposit

The La Coipa ore deposit is part of an epithermal precious metal system located in the Tertiary volcanic belt of northern Chile. Two main mineralized zones are present at La Coipa, Ladera-Farel16n a d Coipa Norte, both hosted by Triassic black shales and sandstones and by late Oligocene to early Miocene tuffs and tuffaceous breccias. Latite dikes and sills and a dacite dome complex are spatially and temporally related to the volcanism that generated the host pyroclastic sequence. K-Ar ages demonstrate that the mineralization process took place during the volcanic event. Mineralization is structurally controlled, mainly by vertical to subvertical, north-south- to northeast-southwest-striking faults and associated fractures. However, the configuration of ore suggests hat there was also an important lithologic ontrol. The orebodies have semitabular to mushroom-shaped forms. Farel16n and the eastern portion of Coipa Norte possess high gold grades associated mainly with advanced argillic alteration (alunite-kaolinite __ _ dickite-quartz) and semitabular forms and are hosted mainly by the Triassic sedimentary rocks. Ladera and western Coipa Norte have high silver/gold ratios and mushroom-shaped forms and are hosted preferentially b the Tertiary pyroclastic unit. Ladera is largely supergen