Gold mineralization characteristics at Serra do Itaberaba, State of São Paulo, Brasil

Abstract

The metavolcanic-sedimentary sequence of the Serra do ltaberaba Group are host to several gold occurrences, the best known being Tapera Grande. There are two main types of gold mineralization: a syngenetic, stratabound, in which gold is scattered in basic and intermediate metavolcaniclastic rocks and meta-exhalites (metacherts with sulfides and turmalinites), and a hydrothermal, epigenetic one, within quartz veins with sulfides, superimposed to the former or associated with shear zones. The former is characterized by the assemblage of pyrrhotite, pyrite and subordinate chalcopyrite as well as by the very fine granulation of the gold. ln the latter, gold occurs free ar associated with copper sulfides (chalcopyrite, covellite and chalcosine) and with quartz. Chemical analyses showed higher contents of copper, lead, zinc and silver in the epigenetic type, while in the syngenetic one are found palladium and high contents of tungsten. Arsenium is absent, in disagreement with other similar deposits.