Gold-Rich Porphyry Systems in the Maricunga Belt, Northern Chile

The Maricunga belt is a linear metallogenic unit defined by at least 14 zones of gold and/ or silver mineralization between latitudes 26 ø and 28 ø S in the Andean Cordillera of northern Chile. After 10 years of exploration, three precious metal deposits are in production, two more have proven resei'ves, and others are being drilled. Total geologic reserves are 420 metric tons of gold and about 14,000 metric tons of silver divided between intrusion-hosted porphyry-type deposits and volcanic-hosted epithermal deposits of high sulfidation, acid sul-fate type. Precious metal mineralization is related to a belt of Miocene volcanic rocks, most of which constitute aseries of large compound stratovolcanoes of calc-alkaline composition. The volcanic rocks overlie unconformably and largely conceal an igneous and sedimentary basement of Paleozoic and Mesozoic age. Volcanic rocks and contained alteration and mineralization are subdivided on the basis of K-Ar dating into partly overlapping, western early Miocene (24-20 Ma) and eastern middle Miocene (14-13 Ma) subbelts. High-angle reverse faulting occurred between these two epochs in response to regional compression induced by subduction zon