| Autor: |
Benjamin Bley de Brito Neves, Othon Henry Leonardos, Antônio Carlos Pedrosa-Soares, Philippe Vidal |
| Rok vydání: |
1998 |
| Předmět: |
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| Zdroj: |
Geology. 26:519 |
| ISSN: |
0091-7613 |
| DOI: |
10.1130/0091-7613(1998)026<0519:norieb>2.3.co;2 |
| Popis: |
The Aracuai (eastern Brazil) and West Congo (southwestern Africa) belts are counterparts of the same Neoproterozoic orogen located between the Sao Francisco and Congo cratons. The Macaubas Group represents a major passive margin sequence and is a key unit for interpreting the evolution of that orogen. The Salinas Formation is the distal rock assemblage of the Macaubas Group and consists of a deep-sea sand-mud sequence, and a volcanic-sedimentary unit called the Ribeirao da Folha facies. The latter includes metamorphosed volcanic-exhalative sediments associated with ocean-floor basalts (amphibolites). The magmatic protoliths of these amphibolites crystallized at about 816 ± 72 Ma (Sm-Nd whole-rock isochron, ϵ Nd(t) =+3.8 ± 0.2). Regional metamorphism reached the amphibolite facies at about 630 Ma (Rb-Sr whole-rock isochron), when slabs of ultramafic rocks were tectonically emplaced over the Ribeirao da Folha facies. We consider this volcanic-sedimentary facies and the coeval slabs of ultramafic rocks to be remnants of a branch of the Adamastor-Brazilide ocean. The extensive occurrence of syntectonic to late tectonic calc-alkalic granitoids along the internal domain of the Aracuai belt implies that a reasonably large amount of ocean crust was consumed, via an east-dipping subduction zone, during formation of the Aracuai–West Congo orogen. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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