Mineralizações auríferas hospedadas na faixa metavulcano-sedimentar Jacuí-Bom Jesus da Penha - Sudoeste de Minas Gerais
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Data
2004-02-27
Autores
Feola, Jorge Luiz [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
As mineralizações auríferas hospedadas na Faixa Metavulcano-Sedimentar Jacuí-Bom Jesus da Penha são controladas tectonicamente pelas zonas de cisalhamento Riacho Fundo, Bom Jesus da Penha e Mumbuca. Nos prospectos da região de Jacuí são caracterizadas estruturas secundárias marcantes, principalmente cisalhantes Riedel de alto ângulo, enquanto naqueles da região de Bom Jesus da Penha/Nova Resende há ausência dessas feições, refletindo o estilo intra- e interzonas de cisalhamento. O processo mineralizante está associado à ação metamórfico-hidrotermal, propiciada pelo evento dínamo-termal local. O condicionamento litológico da mineralização primária é evidenciado principalmente em rochas metassedimentares e hidrotermais, rochas gnáissicas diversas e veios de quartzo. Nessas rochas, o ouro ocorre livre, composicionalmente puro e ainda contendo prata. Entretanto, a ocorrência de aurocuprita/tetra-aurocuprita associada a cuprita, promovida pela alteração supergênica, permite a associação de ouro junto a sulfetos de cobre, que devem corresponder aos níveis mais preservados da mineralização. Os veios de quartzo, comumente contendo sulfetos, carbonatos, filossilicatos, sulfatos e óxidos, são do tipo veios de cisalhamento a localmente do tipo tension gashes, que ocorrem predominantemente em estruturas Riedel do tipo D. Embora parte desses contenham ouro, a mineralização é predominantemente do tipo disseminada, principalmente em muscovita/sericita-quartzo xistos. Embora vários processos de alteração hidrotermal sejam reconhecidos, normalmente apresentam-se não pervasivos. Destaca-se, entretanto, a interação fluido-rocha a partir de litotipos tanto de composição ácida como básica/ultrabásica. São admitidas temperaturas da ordem de 500-600°C para a fase inicial do processo mineralizante...
The gold mineralizations hosted in Jacuí-Bom Jesus da Penha Metavolcano- Sedimentary Belt are controled in the tectonic by Riacho Fundo, Bom Jesus da Penha and Mumbuca shear zones. In the Jacuí region are distinguished remarkable secondary structures, mainly high angle Riedel shears, while in the Bom Jesus da Penha/Nova Resende region there aren't this features, expressing the intrazone and interzone style of shear. The mineralization is associated to metamorphic-hydrothermal process, caused by local dynamo-thermal event. The litologic conditioning of primary mineralization is mainly corroborated in hidrothermal and metassedimentary rocks, several gneissic rocks and quartz veins. I these rocks gold occurs free, pure and with some contents of silver. However, supergenic alteration produces auricupride/tetra-auricupride associated to cuprite. This reaction permits gold and cupper sulphides association, that ought correspond the most preserved mineralization levels. The quartz veins usually contain sulfides, carbonates, philossilicates, sulphates and oxides. This are shear veins to local type D Riedel structure. In spite of gold occurs in some of that veins, the minalization is often disseminated type, mainly in muscovite/sericite-quartz schists. Several hidrothermal alteration process are recognized, but generally to show up not-pervasive. The fluid-rock interation from acid and basic/ultrabasics composition litotypes is emphasized. Temperatures around 500-600ºC are admitted to stage initial of the mineralization. The second stage is associated to sulphides forming and is marked by temperatures of 350- 400ºC. This stage results of more soften P-T conditions and fO2 and fS2 variations. In the last stage is widely hidrothermal, there is not gold and occurs at temperatures between 270 to 310ºC. The fluid involvid in the mineralize process are accepted to aqueous... (Complete abstract, access undermentioned electronic address)
The gold mineralizations hosted in Jacuí-Bom Jesus da Penha Metavolcano- Sedimentary Belt are controled in the tectonic by Riacho Fundo, Bom Jesus da Penha and Mumbuca shear zones. In the Jacuí region are distinguished remarkable secondary structures, mainly high angle Riedel shears, while in the Bom Jesus da Penha/Nova Resende region there aren't this features, expressing the intrazone and interzone style of shear. The mineralization is associated to metamorphic-hydrothermal process, caused by local dynamo-thermal event. The litologic conditioning of primary mineralization is mainly corroborated in hidrothermal and metassedimentary rocks, several gneissic rocks and quartz veins. I these rocks gold occurs free, pure and with some contents of silver. However, supergenic alteration produces auricupride/tetra-auricupride associated to cuprite. This reaction permits gold and cupper sulphides association, that ought correspond the most preserved mineralization levels. The quartz veins usually contain sulfides, carbonates, philossilicates, sulphates and oxides. This are shear veins to local type D Riedel structure. In spite of gold occurs in some of that veins, the minalization is often disseminated type, mainly in muscovite/sericite-quartz schists. Several hidrothermal alteration process are recognized, but generally to show up not-pervasive. The fluid-rock interation from acid and basic/ultrabasics composition litotypes is emphasized. Temperatures around 500-600ºC are admitted to stage initial of the mineralization. The second stage is associated to sulphides forming and is marked by temperatures of 350- 400ºC. This stage results of more soften P-T conditions and fO2 and fS2 variations. In the last stage is widely hidrothermal, there is not gold and occurs at temperatures between 270 to 310ºC. The fluid involvid in the mineralize process are accepted to aqueous... (Complete abstract, access undermentioned electronic address)
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Geologia economica - Brasil, Ouro, Zona de cisalhamento, Química mineral, Hidrotermalismo
Como citar
FEOLA, Jorge Luiz. Mineralizações auríferas hospedadas na faixa metavulcano-sedimentar Jacuí-Bom Jesus da Penha - Sudoeste de Minas Gerais. 2004. xvi, 211 f. Tese (doutorado) - Universidade Estadual Paulista, Instituto de Geociências e Ciências Exatas, 2004.