Elementos traço em pirita por microssonda eletrônica no depósito disseminado X1, Província Aurífera de Alta Floresta (MT), Cráton Amazônico

• Autor(a) principal: Silva, Aline Nayra 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/11449/203400; http://www.athena.biblioteca.unesp.br/exlibris/bd/capelo/2019-05-14/000915015.pdf
• topic: Análise com microssonda; Ouro; Rochas igneas; Petrologia; Microscopia eletrônica de varredura; Crátons; Alta Floresta (MT)

The Alta Floresta Gold Province, located at north of Mato Grosso state, corresponds to a WNW-ESE 500km-long crustal segment inserted in the southernmost sector of the Amazon Craton. It consists of Paleoproterozoic plutonic, volcanic and volcanossedimentary sequences coverd by Mesoproterozoic clastic sediments. The province is limited to the south by the Caiabis Graben, and by the Cachimbo gráben at its northmost edges. Into the province, hundreds of primary small gold-rich deposits occur along the NW-SE Peru-Trairão belt. These gold mineralizations can be grouped into four major groups: (1) Au ± Cu disseminated deposits; (2) vein-type Au ± Cu structurally controlled deposits; (3) Cu + Mo ± Au disseminated deposits; and (4) vein-type Au + Pb + Zn ± Cu deposits. Collectivelly, these deposits represent magmatic-hidrotermal systems similar to gold-rich porphyry deposits (groups I and II) low to intermediate sulphidation epithermal deposits (groups III and IV), for which phyllic alteration (muscovite + quartz + pyrite) represents the major hydrothermal alteraion halo. Into this scenario, this work gols the determination of trace element concentrations in the pyrite crystals from the X1 deposit (Matupá city, MT), that is one of the major Au ± cu disseminated system into the province (group I). Therefore, conventional petrography, SEM and electronic microprobe analisys were performed. The petrography allowed to recognize three distinct textures of pyrite related to the phyllic alteration in the X1 deposit, which include: (1) fine, (2) medium and (3) coarse grained pyrite. The electronic microprobe analysis revel that the Pb (500 to 5510 ppm), Au (200 to 2000), Ti (10 to 90), Ag (40 to 450), Zn (10 to 700 ppm), Cu (90 to 11590 ppm), Ni (100 to 850 ppm) e Co (5960 to 17000 ppm), concentrations are above the detection limit, whereas Al (76 to 152 ppm), As (0 ppm), Sb (30 to 80 ppm) e Cr (20 to 800 ppm) were below the detection limit for the most...