Caracterização petrográfica e química de clorita e mica branca do depósito aurífero do Basílio, Província de Alta Floresta (MT)

• Autor(a) principal: Silva, Felipe Lucio da [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/11449/203402; http://www.athena.biblioteca.unesp.br/exlibris/bd/capelo/2019-05-14/000915018.pdf
• topic: Petrologia; Geoquímica; Mica; Ouro; Mineralogia; Alta Floresta (MT)

The Alta Floresta Gold Province (AFGP), located at north of Mato Grosso State, hosts more than a hundred medium- to high-grade and low tonnage gold-rich deposits. The province is placed at the southernmost portion of the Amazon Craton, where the gold deposits are concentrated along the NW-SE Peru-Trairão belt. Its mineralizations are hosted in Paleoproterozoic plutonic, volcanic and volcano-sedimentary sequences. Into this context, the primary gold deposits can be grouped into the following groups: (1) disseminated Au ± Cu deposits; (2) vein-type Au ± Cu deposits; (3) disseminated Cu + Mo ± Au deposits; and (4) vein-type Au + Pb + Zn ± Au deposits. In common, these deposits share the metalogeny controlled by magmatic-hydrothermal systems similar to Au-porphyry and low- to intermediate sulfidation epithermal systems. Although the major geological features of these deposits are known, mineral chemistry studies are scarce mainly if considered the hydrothermal halos compositions related to the mineralized zones. The chemical analysis of the typical-ocurring minerals from these halos, mainly represented by white mica (phyllic alteration) and chlorite (propylitic and chlroritic alterations) can provide further information about their mineral-forming processes, such as pressure and temperature. This work, therefore, goals the petrographic and chemistry characterizations of the chlorite and white mica from the vein-type Au ± Cu Basílio deposit (group II). Thus, four textural varieties of chlorite (pseudomorphic, venular, anomalous birefringence and intersticial) and four of white mica (lamellar sericite, pseudomorphic sericite, intersticial sericite and subhedral muscovite) were characterized. The chlorite is, generally, characterized as brunsvigite, where the anomalous birrefringence variety is Mg-enriched, while the others, Fe-enriched. The white mica, on the other hand, shows a wide compositional variation, from muscovite-like compositions...