Composição química da clorita e mica branca do depósito paleoproterozóico de Au + metais base do Francisco, Província Aurífera de Alta Floresta (MT)

• Autor(a) principal: Machado, Juliana Martuscelli [UNESP]
• Data de Publicação: 2018
• Tipo de documento: Trabalho de conclusão de curso
• Idioma: por
• Título da fonte: Repositório Institucional da UNESP
• Texto Completo: http://hdl.handle.net/11449/203407; http://www.athena.biblioteca.unesp.br/exlibris/bd/capelo/2019-05-14/000915034.pdf
• topic: Geoquímica; Mica; Ouro; Crátons; Mineralogia; Petrologia; Análise com microssonda; Depositos hidrotermais; Alta Floresta (MT)

The Alta Florest Gold Province (AFGP), located in the north of Mato Grosso State, is comprehended as a crustal segment with approximately 500 km extension and direction WNW-ESE. It is inserted in the south part of the Amazonic Craton, limited to the north by the Cachimbo Graben and at the south by the Caiabis Graben. In the province, there is occurrence of Paleo- and Mesoproterozoic volcanic and volcanic-sedimentary sequences, which contains primary gold mineralizations concentrated along the Peru-Trairão Belt (NWSE). These mineralizations are grouped in four principal groups: (1) disseminated deposits of Au ± Cu; (2) structurally controlled deposits of Au ± Cu; (3) disseminated deposits of Cu + Mo ± Au; and (4) structurally controlled deposits of Au + Pb + Zn ± Cu. Even though the principal geological attributes have already been established, mineral chemistry studies are scant in the province. Thereby, the porpoise of this study is the characterization of chlorite and muscovite of Francisco's deposit (Peixoto de Azevedo city, MT), that takes part in the fourth class of deposits. To elaborate this study, petrography and electron microprobe were used in samples of sericitic and chloritic alterations. In this context, it was possible to identify two typologies of white mica: (1) fibro-muscovite, and (2) sericite; and two varieties of chlorite: (1) low birefringence, and (2) anomaly birefringence. The data indicates a compositional homogeneity between all varieties observed. Therefore, the white mica shows highly fengite components, while the chlorite displays a predominance of ripidolite components. The muscovite geobarometer points pressures of 0.11 to 1.75 kbar (0.41 km to 6.63 km), whilst the chlorite geothermometer indicates temperatures between 184º to 411ºC. In this context, the Francisco's deposit may have been formed in a magmatic-hydrothermal system, under high temperatures, and located in shallow crustal levels, as most...