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Estruturas primárias e tectônicas do Anortosito Capivarita, Pântano Grande (RS): significado e implicações na sua evolução petrológica

2010; Sociedade Brasileira de Geologia; Volume: 40; Issue: 1 Linguagem: Inglês

10.25249/0375-7536.201040199110

2177-4382

Ruy Paulo Philipp, Milton Luiz Liquintinie Formoso, Ivo Dossin, Farid Chemale, Roberto Sacks de Campos,

Geochemistry and Geologic Mapping

The Capivarita Anorthosite is a unit of Mesoproterozoic age constituted by anorthosite with subordinate presence of garnet anorthosite, metagabros and amphibolites. The anorthosite shows intrusive relationship with high degree paragneisses of Várzea do Capivarita Complex and occurs as a roof pendant in the Neoproterozoic Encruzilhada do Sul and Pitangueiras granites. Structural, petrographic and mineralogical studies characterized the anorthosite and amphibolites as magmatism probably related to tholeitic series. The protoliths are dominated by anorthosites with occurrence of garnet anorthosites and rocks rich in Fe-Ti oxides, constituting an association of massif-type anorthosite. The banded structure is defined by regular variations in composition and size of grains, probably related to mineral fractionation process. The structural, petrographic and mineralogical features are similar to anorthosites of paleoproterozoic ages. The dominant presence of anorthosites with associated amphibolites and metagabbros suggests that the main portion of this association can represent plagioclase cumulates generated by magmatic flux and/or flotation by gravitational assent. The primary structural features suggest this magmatism occurred in anorogenic conditions, in a stable environment, probably cratonic. After this crystallization the anorthosite was submited to regional metamorphism of high degree conditions.