Cupriferous cryptomelane originated from weathering of copper ore deposits of Salobo 3α, Serra dos Carajás

Abstract

Geochemical and mineralogical studies of the weathering mantle over the copper mineralized rocks of Salobo 3α, Serra dos Carajás, Brazil, show that copper, released from sulfides by dissolution, accumulates in situ, and is mainly located in three mineralogical phases: silicatic, ferruginous and manganesiferous. Only the manganesiferous phase is treated here. It is a cryptomelane phase (hollandite group) with variable potassium contento Diverse methods (X-ray diffraction, infra-red spectrometry, chemical microprobe) show clearly that cryptomelane contains up to 20 % Cu0.