Contexto geológico e alteração hidrotermal da mineralização aurífera do alvo Estrutura V, greenstone belt de Crixás (GO)

• Autor(a) principal: Ribeiro, Rafael Vieira [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/11449/203411; http://www.athena.biblioteca.unesp.br/exlibris/bd/capelo/2019-05-14/000915049.pdf
• topic: Geologia; Depositos hidrotermais; Mineralogia; Ouro; Minerios; Fácies (Geologia); Geologia economica; Greenstone belts; Crixás (GO)

The Structure V target is located at the Crixás Greenstone Belt, northwest of Goias State, which consist a sedimentary volcanic sequence metamorphosed on greenschist to lower amphibolite facies. This sequence is composed, from the base to the top, by Córrego Alagadinho Formation (komatiites), Rio Vermelho Formation (tholeiitic basalts) and Ribeirão das Antas Formation (carbonaceous phyllites and graywackes). This later hostes an assortment of gold deposits such as the bodies lngá, Palmeiras, Pequizão and Mina III, in order to the district be classified as the sixth largest gold reserve of Brazil. The gold mineralization of Structure V target is genetically associated to thrust fault system named structure V and divided in two main typologies: the former, which is considered as high grade, is hosted by the chlorite­carbonate-talc schist (metakomatiite) and arsenopyrite is the predominant ore mineral. Moreover, this mineral occurs disseminated on the Sn foliation. The second mineralization, classified as low grade, is placed at the contact between the chlorite-carbonate-talc schist and the quarzt-carbonate-tremolite schist (metabasalt), in which pyrrhotite and chalcopyrite are the main ore minerals. Furthermore, three ductile deformational events (Dn1, Dn and Dn+1) and one ruptile event are recognized on the geological setting of the target, in order to that hydrothermal metamorphic system responsible by the mineralization had been act during the Dn event. ln this context, the hydrothermal system promotes sin Dn alteration as carbonization, sulphidation, silicification and biotitization and one phase post Dn that is chloritization. ln addition, the hydrothermal zoning can be used as a prospective method, once the chloratization comprises the most external halo, the biotitization an intermadiate halo and the carbonatization represents the alteration associated with the ore. Finally, the potential source of fluids, Au and S of the system...