Geologia del Porfido Aurifero Verde, Proyecto Refugio, Tercera Region, Chile

Abstract

ABSTRACT. Geology of the gold-bearing porphyry of the Verde Refugio project, northern Chile. The Verde deposit is an early Miocene gold-bearing porphyry located in the Refugio property within the Maricunga Belt. Lithological types within the deposit include a coarse-grained dacitic porphyry, a fine-grained dioritic porphyry and an intrusive breccia formed at the interface between both. There are other dacitic porphyries with post-mineralization intrusion. These intrusive rocks are covered by middle Miocene dacitic flows and pyroclastics of La Laguna volcano. The hypogene alteration includes an early phase: (high temperature, late magmatic) characterized by a chlorite-pyrite-magnetite assemblage and weak copper mineralization. Silicification occurred afterwards in many discrete, gold bearing episodes, the principal one being the developmen: of massive silica with later superimposed quartz veining events. Argillic alteration, marginal to the silicified core, unrelated to gold mineralization and characterized by partial to total alteration of the rock to a clay-pyrite assemblage, occurred at the end of the alteration sequence. Exploration and subsequent evaluation of reserves have concluded in a positive economic feasibility. Geological reserves of 216 miIlion tons at a grade of 0,88 grams per ton containing 190 tons of gold at a cut-off rate of 0,5 grams were identified, of which 166 tons of gold are exploitable.