Rochas metamorficas maficas e ultramaficas do Greenstone Belt Barbacena na região de Itutinga, MG

AUTOR(ES)
DATA DE PUBLICAÇÃO

2000

RESUMO

In the area around ltutinga-Nazareno, Minas Gerais State, at the southeastem limit of São Francisco Craton, there are outcrops of thick successions of volcanic mafic and ultramafic rocks that are the subbject of the present study. This volcano-sedimentary succession is mainly constituted by metabasalts, metakomatiites and minor metassedimentary rocks, and is considered to be part of the Barbacena Greenstone Belt. Intrusive bodies of gabroic composition also occur in the same area. The strip of the volcano-sedimentary rocks is parallel with the regional NE-SW trend in common with other similar greenstone strips in the sorrounding areas. They are bordered and intruded to the NW and SE by granitic rocks (sensu lato). Partially preserved primary structures and textural features indicate a volcanic origin for the ultramafic rocks. A volcanic origin for the amphibolites (metabasalts) was inferred from their fine-grained texture and the c10se spacial relationship with the volcanic ultramafic rocks. The gabroic rocks at times show rare preserved cumulate texture, attesting to their intrusive nature. The volcanic and plutonic rocks were metamorphosed in amphibolite or greenschist facies, or transitional between the two. Two metamorphic phases, MI, M2a and M2b, and some deformational features correlated to the three regionally recognised events, Dn, Dn+1 and Dn+2, were identified. The mafic and ultramafic volcanic and plutonic rocks show tholeiitic composition. The geochemical signature of the metabasalts is similar MORE, and the volcanic ultramafic rocks are c1early komatiitic

ASSUNTO(S)

petrologia geoquimica ouro - minas e mineração - itutinga (mg)

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