Geología y exploración del proyecto Mercedes - Puno

Abstract

Study development starts defining the regional geological framework where the Alto Ayaviri – Azángaro structure on which Project Mercedes is located is and describing its key geological elements. Afterwards, at a local scale are exposed all the works and studies made that lead to the characterization of Project Mercedes; compare it with similar gold fields of Kori Kollo; Kori Chaca in Bolivia and Donlin in Alaska to finally adjust it to a geological model of gold deposit. As a result, by the study of this process we define as a prospective are for gold the strip of Alto Ayaviri – Azángaro. Project Mercedes is located in the South of Peru, in the department of Puno 55 km North from the city of Juliaca. It is located in the high plateau between the Occidental and Oriental Mountain Ranges in the zone called Alto Ayaviri-Azángaro. Predominantly they are Paleozoic terrains in altitudes between 3,000 to 4,700 m.a.s.l. over an extension of 230 km long and between 10 - 20 km wide, whilst the area of the Project is 700 hectares. Project Mercedes is located in the metalogenetic XIX strip of the deposits of tin – copper – tungsten related with intrusive of the Oligocene – Miocene. Has gold mineralization and antimony related with sub-vertical bodies in form of dikes of porphyritic dacite composition, which intrude irregularly the shale and slates of Silurian-Devonian Age belonging to the Chagrapi Formation. In surface the dikes are elongated and follow a direction NNW – SSE preferably. The assembly of hydrothermal alteration is predominantly illita – quartz – pyrite which affect in a greater extent of porphyritic dacite than the sediments. Geochemistry on surface, air reverse drilling and diamond drilling present a good direct correlation between gold – arsenic - antimony, linked to mineralization of arsenopyrite and stibnite. Gold is associated mainly to the pyrite and then to the arsenopyrite as solid solution. The type of mineralization is of disseminated form, with thin veins, micro veins and scarce veins of the “sheeted veins” type of sulfurs associated with quartz. Structural control local indicate a preferential NNW – SSE direction coinciding with the control the regional structure of Alto Ayaviri – Azángaro represented by the Calapuja fault and Chupa fault. Drilling has delimited a body of approximately 1,000 m long between 200 to 300 m wide and 40 to 100 m high with values in gold over 0.5 g/t. The oxidation reach 30 m deep and the main mineralization is in sulfurs. As it did not comply with the Newcrest objectives in 2007 the Project was disesteemed, and explorations were not continued.