Banca de DEFESA: JÉSSICA NERES DOS SANTOS

GREENSTONE BELT GUAJERU, SOUTH PORTION OF THE GAVIÃO BLOCK: GEOLOGICAL, PETROGRAPHIC AND GEOCHEMICAL CHARACTERIZATION

Greenstone Belt, Geochemistry, Contamination, Tectonics

The Guajeru Greenstone belt (GBG) is located in the south-central region of the State of Bahia, in the São Francisco Craton, in the southern part of the Gavião block. Most of the tracks mapped in the GBG correspond to an undivided sequence, consisting of metaultramafic rocks, serpentinites, talc schists associated to a lesser extent with metamafic ones, followed by calc- silicate rocks, banded iron formations, meta-limestones, schists and quartzites to fuchsite. In addition, the lithotypes are also presented as small isolated bodies, dispersedly distributed in the TTG gneiss-migmatitic basement. Based on petrography and lithochemistry it is possible to divide the rocks into metamafic (metagabbro), komatiite metabasalt (tremolite talc, chlorite shale talc) and peridotite metakomatiites (serpentine schist talc, serpentinite) which are high magnesium rocks. In general, the three types of rocks exhibit enrichment in ETRL (light) in relation to ETRP (heavy), they are slightly fractionated. It also shows enrichment in LILE incompatible trace elements compared to HFSE, exhibiting negative anomalies of Nb, Sr, Zr, Eu and positive Nd, Y and Hf. All samples in this study showed values of (La/Sm)n, which contributes to the idea of contamination of material from the crust to komatiiti magma., still at the source of the magma. The data presented suggest that the rocks were generated in a plume and arc interaction environment, where the entire set was added to a continental arc.