Petrografia e geoqu?-mica das rochas metam??ficas intercaladas em gnaisses do Arco Magm??tico de Goi??s na regi?￡o de Indiara (GO)

摘要

In Indiara region (GO), dozens of metamafic rocks lenses of various dimensions (metric to kilometric) occur, intercalated in gneisses of the Goi??s Magmatic Arc and oriented according to the direction of the main foliation (Sn). These lenses consist of amphibolite (amphibole schists and amphibolites), have chemical compositions of sub-alkaline basalts to andesitic basalts and sub-alkaline tholeiitic affinity. The distribution of major and trace elements, as well as rare earth elements (REE), suggests that these rocks are derived from a source with similar geochemical signature. The analyzed rocks are enriched in large ion litophile elements (Cs, Rb, Ba, K, Th and U) in relation to elements of high field strength (Nb, Ta, Zr, Hf and Y) and in relation to REE, Sr, P and Ti, showing weak to medium negative anomalies of Nb, Ta and P and suggesting that these rocks were generated in a magmatic arc environment.