Caracterização petrológica e geoquímica do segmento nordeste dos Diques Arauá

• Autor(a) principal: Santos, Ellen Kelly dos
• Data de Publicação: 2018
• Tipo de documento: Trabalho de conclusão de curso
• Idioma: por
• Título da fonte: Repositório Institucional da UFS
• Texto Completo: http://ri.ufs.br/jspui/handle/riufs/9731
• topic: Geologia; Ensino de geologia; Magmatismo tipo-A; Geoquímica; Petroliféra; Arauá (SE); Magmatism type-A; Toleithic Affinity; CIENCIAS EXATAS E DA TERRA::GEOCIENCIAS::GEOLOGIA::GEOQUIMICA

In this work we studied the dikes between the coutiens of Boquim and Riachão do Dantas (SE) were studied, which correspond to a segment of the Dikes Arauá, which is 6 km NE for the main trend. These dikes occur as small and discontinuous outcrops of irregularly shaped, aligned blocks with an average length of 8 km and direction N30-50W, which cut the orthogneisses of the Complex Rio Real - Itabaianinha - Riachão do Dantas and the granulites of the Complex Granulitic Esplanada - Boquim. In the studied area it was possible to locate six parallel dikes: 4 Rhyolitics, 1 Microgabroic and 1 Andesitic. The rhyolitic dikes are predominantly porphyritic, defined by alkaline feldspar, plagioclase and quartz phenocrysts, immersed in a hemicrystalline matrix that makes up 60% to 80% of the rocks. The microgabroic dike comprises a rock of dark gray coloration, with very fine the porphyritic texture. This rock is essentially composed of plagioclase crystals as well as crystalline crystals of sanidine, quartz and opaque minerals. The andesitic dike consists of plagioclase phenocrysts and vesicles surrounded by a hemicrystalline matrix rich in microclites and crystallites of plagioclase and opaque minerals, with presence of and vesicles. The geochemical data indicate that rhyolitic dikes are acidic rocks with alkaline affinity, with characteristics compatible with A-type magmatism. These rocks have a pattern of Fe enrichment, followed by an impoverishment of Al, which is typical of the toleithic trend. The microgabroic dike is classified as high in magnesium toleithic basalt, in addition to presenting normative quartz and hyperstênio that corroborate with the identified affinity. The andesitic dike was positioned in the line that separates the field of basalts from the field of andesites and basaltic andesites, besides presenting normative quartz and hyperstênio that support a toleítica affinity. In the diagrams of tectonic ambience, the rhyolitic and andesitic dikes show an intraplate environment, while the microgabroic dike presents basalt characteristics of the meso-oceanic mountain range. These rocks show signatures of trace elements marked by negative anomalies of Nb, Ta and Ti, and high levels of LILE, Th and ETRL, thus suggesting that these rocks were formed from a mantle metassomatized by previous subduction or was contaminated by the nesting rock during its final positioning