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Use este identificador para citar ou linkar para este item: https://repositorio.ufba.br/handle/ri/5265
Tipo: Artigo de Periódico
Título: Palaeoproterozoic dome-forming structures related to granulite-facies metamorphism, Jequi´e block, Bahia, Brazil: petrogenetic approaches
Título(s) alternativo(s): Precambrian Research
Autor(es): Barbosa, Johildo Salomão Figueirêdo
Martin, Hervé
Peucat, Jean-Jacques
Autor(es): Barbosa, Johildo Salomão Figueirêdo
Martin, Hervé
Peucat, Jean-Jacques
Abstract: Dome structures in the São Francisco craton (Northeast Brazil), have been identified in the regions of Brejões and Santa Inês within the granulitic Jequié block. Domes are mainly composed of CH6 charnockites, which intrude various granulites of the basement. The Brejões dome is surrounded by a rim of supracrustal rocks. The enderbite–charnockite suites CH1 and CH2, which are partially included in the basement and were previously dated ca 2.8–2.7 Ga, are similar to modern calc-alkaline suites and could be derived by partial melting of an enriched tholeiite (degree of fractionation ca 24–23%). An older Archaean component is suggested by negative εNd values at 2.8–2.7 Ga which range between−1 and−4 and Nd model ages with an average ca 3.1 Ga. These magmatic suites are ascribed to the amphibolite-facies based on preserved prograde mineral assemblages and results of geochemical modelling. The CH6 rocks formed in domes are of granitic composition. They mainly derive from partial melting of the 2.7 Ga CH2 basement suite. The hercynite-quartz assemblage in supracrustal rocks surrounding the Brej˜oes dome suggests very high temperature (>1000 ◦C) for the CH6 magmas which would have induced partial melting in adjacent supracrustal rocks, forming garnet-cordierite-bearing granitic melts. Emplacement of domes is constrained by the age of the granulite facies metamorphism in the Jequié block (ca 2.1 Ga) and the average cooling age of monazite which occurred in the syn-dome charnockite and the surrounding heterogeneous granulites of the basement at 2045±2.5 Ma.Asouthern dome exhibits a younger monazite age of 2026 ± 1 Ma, which may suggest a broader age span for the doming event.
Palavras-chave: Archaean enderbite–charnockite suites
Palaeoproterozoic charnockite domes
Geochemical modelling
Geochronological evidences
Bahia state
Brazil
URI: http://www.repositorio.ufba.br/ri/handle/ri/5265
Data do documento: 2004
Aparece nas coleções:Artigo Publicado em Periódico (IGEO)

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