Petrografia, geoquímica e química mineral do Granito Correas associado as mineralizações de estanho, SW do estado de São Paulo

• Autor(a) principal: Mata, Suelen Portughesi da
• Data de Publicação: 2019
• Tipo de documento: Trabalho de conclusão de curso
• Idioma: por
• Título da fonte: Repositório Institucional da UNESP
• Texto Completo: http://hdl.handle.net/11449/234970
• topic: Geology; Correas Granite; Petrography; Geochemistry; Mineral chemistry; Rochas ígneas; Granito; Granito Correas; Petrografia; Geoquímica; Química mineral

The Correas Granite is located in the northern part of the 1:50.000 Araçaíba Topographic Map (SG-22-XB-II-3) of the IBGE, in the southwest region of the state of São Paulo, in the city of Ribeirão Branco, between the geographic coordinates 24°15'16.24"S/48°54'24.92"O e 24°16'56.38"S/48°57'38.29"O. The granite is located in the south-central Ribeira Belt, in the northern portion of the Apiai Terrain and is related to the granitogenic neoproterozoic evolution of the central Mantiqueira Province, associated with the occurrence of cassiterite and wolframite in greisens. The granite occupies an area of approximately 5 km², has the dimensions of an stock and has elongated ellipitical shape in the ENE-WSW direction. The granite is hosted in the metasediments of the Água Clara Formation and the Três Córregos Granitic Complex. The Correas Granite is represented by three facies and one pegmatitic phase: porphyritic biotite monzogranite, porphyritic biotite-muscovite sienogranite, topaz bearing porphyritic mica-albite granite and pegmatite. The porphyritic biotite monzogranite facies is white-gray to pinkish, isotropic with plagioclase, microcline and globular quartz phenocrysts up to 5mm and the groundmass is fine to medium-grained, and composed of microcline, plagioclase, quartz and biotite and secondary albite and muscovite. The porphyritic biotite-muscovite sienogranite facies is white-gray to redish, isotropic with plagioclase, microcline and globular quartz phenocrysts up to 5mm and the groundmass is fine grained, and composed of microcline, plagioclase, quartz, biotite and muscovite. The topaz bearing porphyritic mica-albite granite facies is white to pinkish, isotropic with microcline and globular quartz phenocrysts up to 7mm and the groundmass is fine grained, and composed of albite, quartz, microcline, micas (zinnwaldite and muscovite) and topaz. The pegmatite facies are characterized by the alternation of quartz and micas bands in which quartz, mica and topaz crystals are well formed and can reach more than 5cm. The Correas granitic rocks belong to a high-K calc-alkaline to shoshonitic potassic magmatism with dominant peraluminous types. The magmatism is compatible with A-type granite and post-colisional to anorogenic intraplaca ambient, with emplacement of the granite massif associated to the transtensive structures correlated to the shear zones in extensional ambient of the colisional event of the Ribeira Orogenesis. The mineral chemistry analyses in the topaz bearing porphyritic mica-albite granite facies prove the sodic character of the plagioclases, with predominantly albite composition, and variation in the composition of the micas, with predominantly zinnwaldite composition in the most evolved facies.