Copper dispersion and accumulation in weathered materiais from copper ores in Brazil

Abstract

Geochemical and mineralogical studies carried out on weathered material at three cupriferous deposits (Chapada Grande - Goiás, Salobo 3A - Pará and Santa Blandina - São Paulo) 100 to verify copper behavior in lateritic weathering profiles. It has been showed that copper retention or mobilization depends on the nature and variety of supergene neoformed phases and on the nature of weathering solutions. In Chapada Grande, goethite is the main secondary phase able to retain copper in weathered mantle, percolating solutions are copper depleted. So, as goethite is not abondant and as its capacity to retain copper is limited, copper is almost totally removed from the weathered material. In Salobo 3A, vermiculite, interestratified biotite-vermiculite and goethite are the main secondary phases that retain copper, and percolating solutions are little richer in copper. So, as phyllosilicates can retain much copper and as there is high contents on goethite through the profile, much of primary copper is fixed on weathered mantle. In Santa Blandina, peculiar conditions lead to very rich copper solutions and to copper silicate (chrysocola) formation at the bottom of the profile. So, copper is accumulated at the bottom of weathered mantle.