GEOLOGIA E PETROGRAFIA DO GARIMPO DE Au ± Cu DA RAIMUNDA, NA PROVÍNCIA MINERAL DE ALTA FLORESTA (MT): Geology and petrography of the Au ± Cu Raimunda Hill, in the Alta Floresta Mineral Province (MT)

Abstract

The Raimunda Garimpo is located in the PMAF, south of the Amazonian Craton, hosted in Granito Novo Mundo. The analyzes carried out showed the occurrence of two main host rocks of the mineralization: (1) tonalite; and (2) granodiorite. Six hydrothermal stages were recognized: (1) sodic alteration; (2) potassic; (3) seritic; (4) propylitic; (5) silica injection; e (6) late veinlets. The gold ore is confined, temporally and spatially associated with quartz ± carbonate veins, which correspond to the 5th alteration stage described. The ore is represented by the paragenesis pyrite ± chalcopyrite ± pyrrhotite ± sphalerite ± hematite ± bismuthinite ± gold. The characteristics of the Raimunda “Garimpo” are similar with the disseminated gold systems confined to veins and quartz stockwork in calc-alkaline granites described in the province. The hypothesis adopted in this work is that the hydrothermal system and the sulphide and mineralized zones of the Raimunda mine formed from the development of an epithermal intermediate sulfidation system that superimposed (telescoped) a possible porphyry-type system.O Garimpo da Raimunda está localizado na PMAF, ao sul do Cráton Amazônico, hospedado no Granito Novo Mundo. As análises feitas evidenciaram a ocorrência de duas rochas hospedeiras principais da mineralização: (1) tonalito; e (2) granodiorito. Foram reconhecidos seis estágios hidrotermais: (1) alteração sódica; (2) alteração potássica; (3) alteração sericítica; (4) alteração propilítica; (5) injeção de sílica; (6) vênulas tardias. O minério aurífero é filonar e está associado a veios de quartzo ± carbonato do 5º estágio de alteração descrito. A paragênse do minério é pirita ± calcopirita ± pirrotita ± esfalerita ± hematita ± bismutinita ± ouro. As análises sugerem que o garimpo se insere no contexto dos sistemas auríferos disseminados e confinados a veios e stockwork de quartzo em granitos descritos na província. A hipótese adotada neste trabalho é de que o sistema hidrotermal e as zonas mineralizadas do garimpo da Raimunda se formaram a partir do desenvolvimento de um sistema epitermal intermediate sulfidation que teria telescopado um possível sistema do tipo pórfiro.  Palavras-chave: Província Mineral de Alta Floresta. Ouro. Alteração hidrotermal. Garimpo da Raimunda.   ABSTRACT - The Raimunda mining is located in the Alta Floresta Gold Province, south of the Amazonian Craton, hosted in Granito Novo Mundo. The analyzes carried out showed the occurrence of two main host rocks of the mineralization: (1) tonalite; and (2) granodiorite. Six hydrothermal stages were recognized: (1) sodic alteration; (2) potassic; (3) seritic; (4) propylitic; (5) silica injection; e (6) late veinlets. The gold ore is confined, temporally and spatially associated with quartz ± carbonate veins, which correspond to the 5th alteration stage described. The ore is represented by the paragenesis pyrite ± chalcopyrite ± pyrrhotite ± sphalerite ± hematite ± bismuthinite ± gold. The characteristics of the Raimunda mining are similar with the disseminated gold systems confined to veins and quartz stockwork in calc-alkaline granites described in the province. The hypothesis adopted in this work is that the hydrothermal system and the sulphide and mineralized zones of the Raimunda mine formed from the development of an epithermal intermediate sulfidation system that superimposed (telescoped) a possible porphyry-type system. Keywords: Alta Floresta Mineral Province. Gold. Hydrothermal alteration. Raimunda mining