DEPOSITIONAL ENVIRONMENTS OF SUPRACRUSTAL METASEDIMENTARY SEQUENCE AND POSSIBLE MODEL FOR ZINC MINERALIZATION OF RIO CLARO AREA, RIO DE JANEIRO STATE (BRAZIL)

This work focuses on Neoproterozoic supracrustal rocks related to Andrelandia megasequence, which are superimposed on the basis represented by neoarchean granulites and palaeoproterozoic ortogneiss, in order to define palaeoenvironments of deposition of metasedimentary rocks and typological model of zinc mineralization of Rio Claro, Rio de Janeiro State, SE of Brazil. Three stratigraphic units in the area were considered for the studies: Valadao, Sao Roque and Lidice. Valadao unit was divided into three subunits: psamitic, psamitic / pelitic and pelitic. On the whole, it represents a turbiditic sequence influenced by underwater hydrothermal exhalations that led to the formation of quartzite with magnetite, considered as banded iron formations. Sao Roque Unit is composed of four subunits (Sao Roque I, II, III and IV) and presents a typical pattern of deposition of low energy environments, in marine deep basins. Gondite, coticules levels and (Mn)-almandine present in the local gneiss mark the manganese exalative contribution in that unit. Lidice unit has different sedimentation palaeoenvironments and is subdivided into Lidice I, II and III. Lidice subunits I and II exhibit quartzite interleaved with pelitic rocks and graphite gneiss, suggesting deposition in deeper environments of the basin, probably related to turbidity currents. In Lidice III subunit, more carbonated and with more quartz, limestone quartzite stand out, which enclose mineralized zones, reflecting depositional environment in shallow platform, possibly involving evaporitic environment, sabkha type. Sulfite mineralization of Rio Claro, associated with platformal rocks intensely metamorphosed and deformed, as well as its local geological context, features similarities with sedimentary exhalative deposits (SEDEX) Zn-Pb-Ag model, Shuswap and Monashee type, present in Monashee and Shuswap Complexes of British Columbia in Canada.