Produção Nacional
Geologia do segmento sul do Orógeno Itabuna-Salvador-Curaçá
2003; Sociedade Brasileira de Geologia; Volume: 33; Issue: 1 Linguagem: Inglês
10.5327/rbg.v33i1.1026
ISSN2317-4889
AutoresJohildo Salomão Figueirêdo Barbosa, Luiz César Corrêa-Gomes, Moacyr Moura Marinho, Fernando César Alves da Silva,
Tópico(s)Geochemistry and Elemental Analysis
ResumoGeological mapping, petrographic, petrochemical, tectonic, geochronological and isotopic studies that have been carried out on the poly-deformed Archean terranes of southern Bahia have discriminated different domains. To the western part (Jequie Block) there occur heterogeneous granulites, from igneous and metasedimentary origin (3.2-2.9Ga) besides enderbitic, charnoenderbitic and charnockitic rock units (2.8-2.7Ga), all of them exihibiting calc-alkaline chemical affinities, with high to intermediary potash contents. To the eastern part (Itabuna-Salvador-Curaca Block), most of the rock units cropping out are metatonalites-metatrondhjemites (2.6-2.5Ga) and metamonzonites (2.4Ga), the first ones presenting calc-alkaline affinities with low potash and the last ones tending to a shonshonitic character. Both types display enclaves of gabbros and granulitized supracrustal rocks. Between the above mentioned blocks there is occurring a narrow belt of quartz-feldspatic rocks, besides some granites (“Band” of Ipiau), all of them under the amphibolite facies of metamorphism. About 2.0-1.9Ga the collision of the two above-mentioned blocks have occurred. Such collision was responsible for the tectonic superposition of blocks and also for the granulitization processes of the southern part of the Itabuna-Salvador-Curaca Block. Nevertheless, the “Band” of Ipiau, positioned between the two blocks remained preserved in the amphibolite facies. During the peak of the metamorphism were generated leucocharnockites, garnet-cordierite bearing types, that have usually been considered of anatetic origin (metasediment derived) as well as charnockites formed by partial melting of the enclosing rocks, these latter usually exihibint very typical oval structures
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