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MAGMATISMO PÓS-PALEOZÓICO NO NORDESTE ORIENTAL DO BRASIL

1988; Sociedade Brasileira de Geologia; Volume: 18; Issue: 4 Linguagem: Inglês

10.25249/0375-7536.1988451462

2177-4382

Fernando Flávio Marques de Almeida, Celso Dal Ré Carneiro, Delzio de Lima Machado, Lauro Kazumi Dehira,

Geochemistry and Geologic Mapping

Since the Jurassic, the area of Northeastern Brazil was affected by several magmatic events, both intrusive and effusive ones. The ages of the igneous bodies are not perfectly known, but it can be stated that some sedimentary basins accomodated prominent part of the geologic record from the igneous activity. The area north to the 8°S parallel was more intenselly affected, comprising deposits in the Parnaíba, Potiguar, and Lavras da Mangabeira basins. The occurrences are relatively scattered on Precambrian areas, restricted to zones very far from the São Francisco Craton. There are three main age groups. The Jure-Cretaceous bodies (pre-Aptian) are composed of tholeiitic basalts normally without olivine. The Albian and Tertiary ones usually exhibit modal olivine and alkaline composition. It seems that a quiet phase occurred comprising the Neocretaceous and the Paleocen. Based on aeromagnetic and geologic maps at a regional scale,it has been possible to show that some areas were strongly affected by igneous activity. Part of them can be followed along hundreds of kilometers, in a shape of igneous allignements. The most expressive are the Rio Ceará-Mirim, the Mecejana-Fernando de Noronha, both trending E-W, and Macau-Queimadas, trending NNW. The former is related to Neocomian, and the others belong to the Tertiary. There are no Quaternary igneous activity in the continental area, but some oceanic islands were evolved until the end of the tertiary.