Prepared and published jointly by the geological surveys of Argentina, Chile, Colombia, Peru, and the United States

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A quantitative resource assessment to be published this fall identifies and evaluates 26 tracts in South America where the geology isconsidered permissive for the occurrence of porphyry copper deposits. For each tract, information is provided on: (1) the rationale fordelineating the tract, (2) examples of important deposits in the tract, (3) the rationale for choosing the mineral deposit model used forthe assessment, (4) exploration history, and (5) expected spatial distribution of undiscovered deposits in the tract. The scale used toevaluate geologic information and define tracts is 1:1,000,000. There are about 600 million tonnes of copper in known porphyry copper deposits in South America. This study estimates there areapproximately 720 million tonnes of additional copper in undiscovered porphyry copper deposits, yielding a combined endowment ofabout 1.3 billion tonnes of copper. There...

The Neogene-Quarernary volcanic complex of thc central Andes contains hundreds of hydrothermally altered zones, severa! of which are associated with world-dass cpichcrmal precious-metal deposits, but most of which are either unexplored or inadcquately explorcd. Thcse young volcanic rocks, chiefly andesitic to dacitic lavas and rhyolitic ash-ílow tuffs, ·extenct· over an area of about 300,000 km2 in the Andean Highlands of southern Perú, northcrn Chile, western Bolivia, and northwestern Argentina. At least a dozen majar deposits have been discovered in che young volcanic complex since the late 1970's by exploration programs stimulated by the phenomenal rise in gold and silver prices. Not only are eruptive centers in che complex prime exploration targets, but thc volcanic complcx covers older rocks and associated mineral deposits of one of the world's greatcst metallogenic provinces. F...

El Complejo Volcánico Cerros Bravos (Oligoceno-Mioceno) es un conjunto de lavas y domos dacítico-andesíticos calcoalcalinos de gran extensión (450 km2) ubicado a unos 140 km al este de Copiapó, Chile, que integra la Franja de Maricunga, cadena volcánica neógena que representa un arco pluto-volcánico de margen continental. Los análisis radiométricos K-Ar señalan que el complejo volcánico Cerros Bravos estuvo activo entre los 26-18 Ma (Oligoceno-Mioceno inferior) en tanto que el complejo La Coipa registra actividad hasta el Mioceno medio (15 Ma), y desde allí hacia el sur los centros volcánicos presentan edades entre 16 y 6 Ma. El complejo hospeda la zona de alteración hidrotermal del Prospecto Esperanza, sistema epitermal del tipo sulfato-ácido con mineralización de oro y plata controlada estructuralmente y asociada a una intensa silicificación y argilización con calcol...