Early weathering of palladium gold under lateritic conditions, Maquiné Mine, Minas Gerais, Brazil.
Autor(a) principal: | |
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Data de Publicação: | 2000 |
Outros Autores: | , , , |
Tipo de documento: | Artigo |
Idioma: | eng |
Título da fonte: | Repositório Institucional da UFOP |
Texto Completo: | http://www.repositorio.ufop.br/handle/123456789/1364 |
Resumo: | Since the 80's, studies have shown that Au is mobile in supergene lateritic sur®cial conditions. They are based either on petrological, thermodynamic studies, or experimental works. In contrast, few studies have been done on the mobility of the Pt group elements (PGE). Moreover, at the present time, no study has addressed the di€erential mobility of Au, Ag and Pd from natural alloys in the supergene environment. The aim of this study is to understand the supergene behavior, in lateritic conditions, of Au±Ag±Pd alloys of the Au ore locally called Jacutinga at the Maquine Mine, Iron Quadrangle, Minas Gerais state, Brazil. The ®eld work shows that the host rock is a ``Lake Superior type'' banded iron formation (BIF) and that the Au mineralization originates from sul®de-barren hydrothermal processes. Primary Ag±Pd-bearing Au has developed as xenomorphous particles between hematite and quartz grains. The petrological study indicates that the most weathered primary Au particles with rounded shapes and pitted surfaces were found, under the duricrust, within the upper friable saprolite. This layer, however is not the most weathered part of the lateritic mantle, but it is where the quartz dissolution resulting porosity is the most developed. The distribution of Au contents in the weathered rocks are controlled by the initial hydrothermal primary pattern. No physical dispersion has been found. Most of the particles are residual and very weakly weathered. This characterizes early stages of Au particle weathering in agreement with the relatively low weathering gradient of the host itabiritic formations that leads essentially to the development of isostructural saprolite lateritic mantle. Limited dissolution of primary Au particles issued from the friable saprolite induces Pd±Ag depleted rims compared to primary Au particle Pd±Ag contents.In addition, limited very short distance in situ dissolution/reprecipitation processes have been found at depth within the primary mineralization, as illustrated by tiny supergene, almost pure, Au particles. The supergene mobility order Pd> Ag> Au as re¯ecting early weathering stages of Au±Ag±Pd alloys under lateritic conditions is proposed. |
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Varajão, César Augusto ChicarinoColin, FabriceVieillard, PhillipMelfi, Adolpho JoséNahon, Daniel2012-09-06T14:03:32Z2012-09-06T14:03:32Z2000VARAJÃO, C. A. C. et al. Early weathering of palladium gold under lateritic conditions, Maquiné Mine, Minas Gerais, Brazil. Applied Geochemistry, v. 15, n. 2, p. 245–263, fev. 2000. Disponível em: <https://www.sciencedirect.com/science/article/pii/S0883292799000384>. Acesso em: 06 set. 2012.08832927http://www.repositorio.ufop.br/handle/123456789/1364Since the 80's, studies have shown that Au is mobile in supergene lateritic sur®cial conditions. They are based either on petrological, thermodynamic studies, or experimental works. In contrast, few studies have been done on the mobility of the Pt group elements (PGE). Moreover, at the present time, no study has addressed the di€erential mobility of Au, Ag and Pd from natural alloys in the supergene environment. The aim of this study is to understand the supergene behavior, in lateritic conditions, of Au±Ag±Pd alloys of the Au ore locally called Jacutinga at the Maquine Mine, Iron Quadrangle, Minas Gerais state, Brazil. The ®eld work shows that the host rock is a ``Lake Superior type'' banded iron formation (BIF) and that the Au mineralization originates from sul®de-barren hydrothermal processes. Primary Ag±Pd-bearing Au has developed as xenomorphous particles between hematite and quartz grains. The petrological study indicates that the most weathered primary Au particles with rounded shapes and pitted surfaces were found, under the duricrust, within the upper friable saprolite. This layer, however is not the most weathered part of the lateritic mantle, but it is where the quartz dissolution resulting porosity is the most developed. The distribution of Au contents in the weathered rocks are controlled by the initial hydrothermal primary pattern. No physical dispersion has been found. Most of the particles are residual and very weakly weathered. This characterizes early stages of Au particle weathering in agreement with the relatively low weathering gradient of the host itabiritic formations that leads essentially to the development of isostructural saprolite lateritic mantle. Limited dissolution of primary Au particles issued from the friable saprolite induces Pd±Ag depleted rims compared to primary Au particle Pd±Ag contents.In addition, limited very short distance in situ dissolution/reprecipitation processes have been found at depth within the primary mineralization, as illustrated by tiny supergene, almost pure, Au particles. The supergene mobility order Pd> Ag> Au as re¯ecting early weathering stages of Au±Ag±Pd alloys under lateritic conditions is proposed.Early weathering of palladium gold under lateritic conditions, Maquiné Mine, Minas Gerais, Brazil.info:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/articleO periódico Applied Geochemistry concede licença ao repositório institucional da Universidade Federal de Ouro Preto para depósito deste artigo. Número da licença: 3335441070423.info:eu-repo/semantics/openAccessengreponame:Repositório Institucional da UFOPinstname:Universidade Federal de Ouro Preto (UFOP)instacron:UFOPLICENSElicense.txtlicense.txttext/plain; charset=utf-81748http://www.repositorio.ufop.br/bitstream/123456789/1364/5/license.txt8a4605be74aa9ea9d79846c1fba20a33MD55CC-LICENSElicense_urllicense_urltext/plain; charset=utf-843http://www.repositorio.ufop.br/bitstream/123456789/1364/2/license_url5134edb0a80711cbbaa5247c36025151MD52ORIGINALARTIGO_EarlyWeatheringPalladium.pdfARTIGO_EarlyWeatheringPalladium.pdfapplication/pdf671599http://www.repositorio.ufop.br/bitstream/123456789/1364/1/ARTIGO_EarlyWeatheringPalladium.pdf8f8d68139ae8b18c3fbe8b889d37a141MD51123456789/13642019-03-08 10:05:29.687oai:localhost: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Repositório InstitucionalPUBhttp://www.repositorio.ufop.br/oai/requestrepositorio@ufop.edu.bropendoar:32332019-03-08T15:05:29Repositório Institucional da UFOP - Universidade Federal de Ouro Preto (UFOP)false |
dc.title.pt_BR.fl_str_mv |
Early weathering of palladium gold under lateritic conditions, Maquiné Mine, Minas Gerais, Brazil. |
title |
Early weathering of palladium gold under lateritic conditions, Maquiné Mine, Minas Gerais, Brazil. |
spellingShingle |
Early weathering of palladium gold under lateritic conditions, Maquiné Mine, Minas Gerais, Brazil. Varajão, César Augusto Chicarino |
title_short |
Early weathering of palladium gold under lateritic conditions, Maquiné Mine, Minas Gerais, Brazil. |
title_full |
Early weathering of palladium gold under lateritic conditions, Maquiné Mine, Minas Gerais, Brazil. |
title_fullStr |
Early weathering of palladium gold under lateritic conditions, Maquiné Mine, Minas Gerais, Brazil. |
title_full_unstemmed |
Early weathering of palladium gold under lateritic conditions, Maquiné Mine, Minas Gerais, Brazil. |
title_sort |
Early weathering of palladium gold under lateritic conditions, Maquiné Mine, Minas Gerais, Brazil. |
author |
Varajão, César Augusto Chicarino |
author_facet |
Varajão, César Augusto Chicarino Colin, Fabrice Vieillard, Phillip Melfi, Adolpho José Nahon, Daniel |
author_role |
author |
author2 |
Colin, Fabrice Vieillard, Phillip Melfi, Adolpho José Nahon, Daniel |
author2_role |
author author author author |
dc.contributor.author.fl_str_mv |
Varajão, César Augusto Chicarino Colin, Fabrice Vieillard, Phillip Melfi, Adolpho José Nahon, Daniel |
description |
Since the 80's, studies have shown that Au is mobile in supergene lateritic sur®cial conditions. They are based either on petrological, thermodynamic studies, or experimental works. In contrast, few studies have been done on the mobility of the Pt group elements (PGE). Moreover, at the present time, no study has addressed the di€erential mobility of Au, Ag and Pd from natural alloys in the supergene environment. The aim of this study is to understand the supergene behavior, in lateritic conditions, of Au±Ag±Pd alloys of the Au ore locally called Jacutinga at the Maquine Mine, Iron Quadrangle, Minas Gerais state, Brazil. The ®eld work shows that the host rock is a ``Lake Superior type'' banded iron formation (BIF) and that the Au mineralization originates from sul®de-barren hydrothermal processes. Primary Ag±Pd-bearing Au has developed as xenomorphous particles between hematite and quartz grains. The petrological study indicates that the most weathered primary Au particles with rounded shapes and pitted surfaces were found, under the duricrust, within the upper friable saprolite. This layer, however is not the most weathered part of the lateritic mantle, but it is where the quartz dissolution resulting porosity is the most developed. The distribution of Au contents in the weathered rocks are controlled by the initial hydrothermal primary pattern. No physical dispersion has been found. Most of the particles are residual and very weakly weathered. This characterizes early stages of Au particle weathering in agreement with the relatively low weathering gradient of the host itabiritic formations that leads essentially to the development of isostructural saprolite lateritic mantle. Limited dissolution of primary Au particles issued from the friable saprolite induces Pd±Ag depleted rims compared to primary Au particle Pd±Ag contents.In addition, limited very short distance in situ dissolution/reprecipitation processes have been found at depth within the primary mineralization, as illustrated by tiny supergene, almost pure, Au particles. The supergene mobility order Pd> Ag> Au as re¯ecting early weathering stages of Au±Ag±Pd alloys under lateritic conditions is proposed. |
publishDate |
2000 |
dc.date.issued.fl_str_mv |
2000 |
dc.date.accessioned.fl_str_mv |
2012-09-06T14:03:32Z |
dc.date.available.fl_str_mv |
2012-09-06T14:03:32Z |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
dc.type.driver.fl_str_mv |
info:eu-repo/semantics/article |
format |
article |
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publishedVersion |
dc.identifier.citation.fl_str_mv |
VARAJÃO, C. A. C. et al. Early weathering of palladium gold under lateritic conditions, Maquiné Mine, Minas Gerais, Brazil. Applied Geochemistry, v. 15, n. 2, p. 245–263, fev. 2000. Disponível em: <https://www.sciencedirect.com/science/article/pii/S0883292799000384>. Acesso em: 06 set. 2012. |
dc.identifier.uri.fl_str_mv |
http://www.repositorio.ufop.br/handle/123456789/1364 |
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08832927 |
identifier_str_mv |
VARAJÃO, C. A. C. et al. Early weathering of palladium gold under lateritic conditions, Maquiné Mine, Minas Gerais, Brazil. Applied Geochemistry, v. 15, n. 2, p. 245–263, fev. 2000. Disponível em: <https://www.sciencedirect.com/science/article/pii/S0883292799000384>. Acesso em: 06 set. 2012. 08832927 |
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