The Cristalino IOCG deposit: an example of multi-stage events of hydrothermal alteration and copper mineralization

• Autor(a) principal: Craveiro,Gustavo Souza
• Data de Publicação: 2019
• Outros Autores: Xavier,Roberto Perez, Villas,Raimundo Netuno Nobre
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Brazilian Journal of Geology
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S2317-48892019000100308
• topic: Iron oxide-copper-gold; Metallogenesis; Hydrothermal system; Neoarchean; Carajás Province

Abstract The Cristalino deposit is located 40 km east of Sossego mine, Carajás. The orebody lies along a NW-SE-striking shear zone and is mainly hosted by the Neoarchean bi-modal volcanics of the Grão Pará Group. Field work and petrographic data seconded by SEM-EDS analysis allowed recognizing an early sodic metasomatism that was followed by calcic-ferric, potassic and propylitic alterations, and finally by carbonatization. The volcanic rocks were altered under deformation regimes that changed from ductile-brittle to brittle. The deposit resulted from two mineralizing stages. The early stage took place at a greater depth and produced an ore association composed chiefly of chalcopyrite, pyrite, and magnetite as disseminations, breccia and veins particularly in Ca-Fe altered rocks. The later stage occurred at a shallower depth and formed a practically magnetite-free ore association, consisting essentially of chalcopyrite ± pyrite ± hematite in breccias and veins generated mostly during the potassic alteration. These ore associations indicate that the hydrothermal system evolved with temperature decrease and increase in fO 2, Cu/Fe ratio and sulfur activity. Cristalino is conceived as a multi-stage IOCG deposit similar to others lying in the Carajás E-W corridor of IOCG systems.