Química mineral da clorita e mica branca do depósito paleoproterozóico do Luizão, Província Aurífera de Alta Floresta (MT), sul do Cráton Amazônico

• Autor(a) principal: Perez, Andres Isquierdo [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/11449/203401; http://www.athena.biblioteca.unesp.br/exlibris/bd/capelo/2019-05-14/000915016.pdf
• topic: Mineralogia; Geoquímica; Mica; Ouro; Crátons; Petrologia; Análise com microssonda; Alta Floresta (MT)

The Alta Floresta Gold Province (AFGP), north of Mato Grosso State, represents a WNW-ESE 500km long crustal segment located in the southernmost sector of the Amazon Craton. It consists of Paleoproterozoic plutonic, volcanic and volcanissedimentary sequences, limited to the south by the Caiabis Graben and by the Cachimbo Graben at its northmost edges. More than a hundred small primary gold-rich deposits along the NW-SE Peru-Trairão belt occur in the Province. In this context, its primary mineralizations can be further grouped into four major groups: (1) Au ± Cu disseminated deposits; (2) Au ± Cu structurally controlled deposits; (3) Cu + Mo ± Au disseminated deposits; and (4) vein-type Au + Pb + Zn ± Cu. Typical magmatic-hydrothermal haloes similar to the Au-porphyry and epithermal deposits are reported in the province, and represent different evolutionary stages of the mineralizing fluid. The phyllic alteration, for instance, represents one of the earliest hydrothermal stages, into a moderate temperature and acid pH proxies, whereas, the propylitic and chloritic alterations represent the final hydrothemal fluid circulation, therefore, neutral to alkaline pH and cooler fluids. In this scenario, although the major geological attributes for the gold deposits of the province be well-understood, mineral chemistry studies are still scarce. Therefore, the study in mineral chemistry of the chlorite and white mica of the Luizão deposit (group I), aimed to characterize different mineral textures and estimate the T e P forming conditions of these minerals, respectively. Applying petrographic and microprobe analyzes, this study was able to distinct four textures of chlorite, all related to the propylic alteration: (1) anhedral, (2) anomalous, (3) fibrous and (4) venular; besides five textures of white mica associated to the pyllic alteration: (1) fibrous-muscovite, (2) fringe muscovite, (3) subhedral muscovite, (4) venular muscovite and (5) sericite...