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

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 CaFe 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.

Blue quartz in Brazil: the Rio dos Remédios occurrence – preliminary study

“…Out of the 19 Brazilian occurrences, nine show an apparent connection to various mineral deposits as follows: Sn -Soledade, Serra da Mesa, Sucuri, Mangabeira, Pedra Branca (Lenharo et al, 2002) and Riacho dos Cavalos (Sparrenberger & Tassinari, 1999); Au -the Cristalino Deposit (Craveiro et al, 2019) and Lagoa do Gato (Mello et al, 2006); U -São Timóteo (Cordani et al, 1992). Similar associations have also been observed in Canada, South Africa and Australia.…”

Evolution of structures and hydrothermal alteration in a Palaeoproterozoic supracrustal belt: Constraining paired deformation–fluid flow events in an Fe and Cu–Au prospective terrain in northern Sweden

“…For example, features such as variably distributed sodic and potassic alteration, the bimodal character of host volcanic rocks, the spatial proximity of deformation zones, and Cu-Au mineralization conform with the IOCG mineral system model defined by Skirrow et al (2019) and mimic the character of other IOCG-mineralized terrains in Brazil (e.g. deMelo et al, 2017;Craveiro et al, 2019), Australia (e.g. Skirrow et al, 2019), Canada (e.g.…”