Origin of the CO2-only fluid inclusions in the Palaeoproterozoic Carará vein-quartz gold deposit, Ipitinga Auriferous District, SE-Guiana Shield, Brazil: Implications for orogenic gold mineralisation
Autor(a) principal: | |
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Data de Publicação: | 2010 |
Outros Autores: | |
Tipo de documento: | Artigo |
Idioma: | eng |
Título da fonte: | Repositório Institucional de Geociências - RIGEO |
Texto Completo: | https://rigeo.cprm.gov.br/handle/doc/570 |
Resumo: | The Carará gold deposit, located in the Ipitinga Auriferous District, south-eastern portion of the Guiana Shield, northern Brazil, is a typical orogenic, greenstone-hosted, auriferous quartz vein. Mineralisation was post-metamorphic and syn-tectonic in relation to the host Palaeoproterozoic (ca. 2.03 Ga) shear zone developed close to the tectonic boundary between a Palaeoproterozoic continental arc and an Archaean block. The deposit style is very simple, consisting of a quartz vein and its hydrothermal envelope, which is composed of muscovite and tourmaline; sulphides are rare. Muscovite and tourmaline, in addition to gold,fill small fractures in the quartz vein. The fluid inclusion assemblage trapped in high- and low-grade portions of the Au–quartz vein is rather enigmatic, consisting of one-phase CO2 inclusions with no visible water at room or sub-zero temperatures, although small amounts of water have been detected by micro-Raman analysis. In this aspect Carará differs from the other gold showings in the same district, which are characterized by abundant aqueous-carbonic fluid inclusions. The carbonic fluid is composed predominantly of CO2 in addition to b2 mol.% N2 and traces of CH4 and C2H6. The carbonic fluid show very variable densities, which is interpreted to result from post-entrapment reequilibration. Inclusions in the high-grade quartz are the densest (0.89 to 1.07 g/cm3) and with less effects of re-equilibration. These inclusions approximate the physico-chemical characteristics of the parental fluid that started to be trapped at least around the amphibolite facies metamorphic conditions and then followed a retrograde path. Most of the inclusions appear to have been trapped and/or re-equilibrated at 350 to 475 °C and 1.8 to 3.6 kbar, which implies a 7 to 12 km depth of vein formation and gold mineralisation. Both phase separation of a carbonic-aqueous fluid (XCO2N0.8) and the existence of an originally CO2-dominated fluid could account for the observed fluid inclusion properties and the absence of H2O-bearing inclusions in the mineralised vein. The fluid inclusion characteristics, combined with published geological and isotopic information, indicate a deep-seated source for CO2 that could be mantle, magmatic or metamorphic in origin. We suggest that the likely sources are fluid produced by the 2.07 Ga-old charnockites that occur in the region and/or the coeval high grade metamorphism that is widespread in the Guiana Shield |
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KLEIN, Evandro LuizFUZIKAWA, Kazuo2013-12-19T16:32:42Z2013-12-19T16:32:42Z2010KLEIN, Evandro Luiz; FUZIKAWA, Kazuo. Origin of the CO2-only fluid inclusions in the Palaeoproterozoic Carará vein-quartz gold deposit, Ipitinga Auriferous District, SE-Guiana Shield, Brazil: Implications for orogenic gold mineralisation. Ore Geology Reviews, Amsterdam, v.37, n.1, p.31-40, 2010.01691368https://rigeo.cprm.gov.br/handle/doc/570The Carará gold deposit, located in the Ipitinga Auriferous District, south-eastern portion of the Guiana Shield, northern Brazil, is a typical orogenic, greenstone-hosted, auriferous quartz vein. Mineralisation was post-metamorphic and syn-tectonic in relation to the host Palaeoproterozoic (ca. 2.03 Ga) shear zone developed close to the tectonic boundary between a Palaeoproterozoic continental arc and an Archaean block. The deposit style is very simple, consisting of a quartz vein and its hydrothermal envelope, which is composed of muscovite and tourmaline; sulphides are rare. Muscovite and tourmaline, in addition to gold,fill small fractures in the quartz vein. The fluid inclusion assemblage trapped in high- and low-grade portions of the Au–quartz vein is rather enigmatic, consisting of one-phase CO2 inclusions with no visible water at room or sub-zero temperatures, although small amounts of water have been detected by micro-Raman analysis. In this aspect Carará differs from the other gold showings in the same district, which are characterized by abundant aqueous-carbonic fluid inclusions. The carbonic fluid is composed predominantly of CO2 in addition to b2 mol.% N2 and traces of CH4 and C2H6. The carbonic fluid show very variable densities, which is interpreted to result from post-entrapment reequilibration. Inclusions in the high-grade quartz are the densest (0.89 to 1.07 g/cm3) and with less effects of re-equilibration. These inclusions approximate the physico-chemical characteristics of the parental fluid that started to be trapped at least around the amphibolite facies metamorphic conditions and then followed a retrograde path. Most of the inclusions appear to have been trapped and/or re-equilibrated at 350 to 475 °C and 1.8 to 3.6 kbar, which implies a 7 to 12 km depth of vein formation and gold mineralisation. Both phase separation of a carbonic-aqueous fluid (XCO2N0.8) and the existence of an originally CO2-dominated fluid could account for the observed fluid inclusion properties and the absence of H2O-bearing inclusions in the mineralised vein. The fluid inclusion characteristics, combined with published geological and isotopic information, indicate a deep-seated source for CO2 that could be mantle, magmatic or metamorphic in origin. We suggest that the likely sources are fluid produced by the 2.07 Ga-old charnockites that occur in the region and/or the coeval high grade metamorphism that is widespread in the Guiana ShieldElsevierDEPÓSITOS DE OUROZONA DE CISALHAMENTOINCLUSÕES FLUIDASQUARTZOPALEOPROTEROZOICOGUIANASBRASILOrigin of the CO2-only fluid inclusions in the Palaeoproterozoic Carará vein-quartz gold deposit, Ipitinga Auriferous District, SE-Guiana Shield, Brazil: Implications for orogenic gold mineralisationinfo:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/articleAmsterdamengreponame:Repositório Institucional de Geociências - RIGEOinstname:Companhia de Pesquisa de Recursos Minerais (CPRM)instacron:CPRMinfo:eu-repo/semantics/openAccessTEXTart_klein10.pdf.txtart_klein10.pdf.txtExtracted texttext/plain56865http://rigeo.cprm.gov.br/jspui/bitstream/doc/570/2/art_klein10.pdf.txt90882a23971ef529a83112d6f292e24eMD52THUMBNAILart_klein10.pdf.jpgart_klein10.pdf.jpgGenerated Thumbnailimage/jpeg1529http://rigeo.cprm.gov.br/jspui/bitstream/doc/570/3/art_klein10.pdf.jpg3d7297dd06d2420796d2bcd5be7ed3c3MD53ORIGINALart_klein10.pdfart_klein10.pdfproducao cientificaapplication/pdf1759726http://rigeo.cprm.gov.br/jspui/bitstream/doc/570/1/art_klein10.pdf381fd0b1f616b84365fafa3ec94e6ed5MD51doc/5702023-02-13 11:13:10.859oai:rigeo.sgb.gov.br:doc/570Repositório InstitucionalONGhttp://rigeo.cprm.gov.br/oai/requestrigeo@sgb.gov.bropendoar:2023-02-13T14:13:10Repositório Institucional de Geociências - RIGEO - Companhia de Pesquisa de Recursos Minerais (CPRM)false |
dc.title.none.fl_str_mv |
Origin of the CO2-only fluid inclusions in the Palaeoproterozoic Carará vein-quartz gold deposit, Ipitinga Auriferous District, SE-Guiana Shield, Brazil: Implications for orogenic gold mineralisation |
title |
Origin of the CO2-only fluid inclusions in the Palaeoproterozoic Carará vein-quartz gold deposit, Ipitinga Auriferous District, SE-Guiana Shield, Brazil: Implications for orogenic gold mineralisation |
spellingShingle |
Origin of the CO2-only fluid inclusions in the Palaeoproterozoic Carará vein-quartz gold deposit, Ipitinga Auriferous District, SE-Guiana Shield, Brazil: Implications for orogenic gold mineralisation KLEIN, Evandro Luiz DEPÓSITOS DE OURO ZONA DE CISALHAMENTO INCLUSÕES FLUIDAS QUARTZO PALEOPROTEROZOICO GUIANAS BRASIL |
title_short |
Origin of the CO2-only fluid inclusions in the Palaeoproterozoic Carará vein-quartz gold deposit, Ipitinga Auriferous District, SE-Guiana Shield, Brazil: Implications for orogenic gold mineralisation |
title_full |
Origin of the CO2-only fluid inclusions in the Palaeoproterozoic Carará vein-quartz gold deposit, Ipitinga Auriferous District, SE-Guiana Shield, Brazil: Implications for orogenic gold mineralisation |
title_fullStr |
Origin of the CO2-only fluid inclusions in the Palaeoproterozoic Carará vein-quartz gold deposit, Ipitinga Auriferous District, SE-Guiana Shield, Brazil: Implications for orogenic gold mineralisation |
title_full_unstemmed |
Origin of the CO2-only fluid inclusions in the Palaeoproterozoic Carará vein-quartz gold deposit, Ipitinga Auriferous District, SE-Guiana Shield, Brazil: Implications for orogenic gold mineralisation |
title_sort |
Origin of the CO2-only fluid inclusions in the Palaeoproterozoic Carará vein-quartz gold deposit, Ipitinga Auriferous District, SE-Guiana Shield, Brazil: Implications for orogenic gold mineralisation |
author |
KLEIN, Evandro Luiz |
author_facet |
KLEIN, Evandro Luiz FUZIKAWA, Kazuo |
author_role |
author |
author2 |
FUZIKAWA, Kazuo |
author2_role |
author |
dc.contributor.author.fl_str_mv |
KLEIN, Evandro Luiz FUZIKAWA, Kazuo |
dc.subject.por.fl_str_mv |
DEPÓSITOS DE OURO ZONA DE CISALHAMENTO INCLUSÕES FLUIDAS QUARTZO PALEOPROTEROZOICO GUIANAS BRASIL |
topic |
DEPÓSITOS DE OURO ZONA DE CISALHAMENTO INCLUSÕES FLUIDAS QUARTZO PALEOPROTEROZOICO GUIANAS BRASIL |
description |
The Carará gold deposit, located in the Ipitinga Auriferous District, south-eastern portion of the Guiana Shield, northern Brazil, is a typical orogenic, greenstone-hosted, auriferous quartz vein. Mineralisation was post-metamorphic and syn-tectonic in relation to the host Palaeoproterozoic (ca. 2.03 Ga) shear zone developed close to the tectonic boundary between a Palaeoproterozoic continental arc and an Archaean block. The deposit style is very simple, consisting of a quartz vein and its hydrothermal envelope, which is composed of muscovite and tourmaline; sulphides are rare. Muscovite and tourmaline, in addition to gold,fill small fractures in the quartz vein. The fluid inclusion assemblage trapped in high- and low-grade portions of the Au–quartz vein is rather enigmatic, consisting of one-phase CO2 inclusions with no visible water at room or sub-zero temperatures, although small amounts of water have been detected by micro-Raman analysis. In this aspect Carará differs from the other gold showings in the same district, which are characterized by abundant aqueous-carbonic fluid inclusions. The carbonic fluid is composed predominantly of CO2 in addition to b2 mol.% N2 and traces of CH4 and C2H6. The carbonic fluid show very variable densities, which is interpreted to result from post-entrapment reequilibration. Inclusions in the high-grade quartz are the densest (0.89 to 1.07 g/cm3) and with less effects of re-equilibration. These inclusions approximate the physico-chemical characteristics of the parental fluid that started to be trapped at least around the amphibolite facies metamorphic conditions and then followed a retrograde path. Most of the inclusions appear to have been trapped and/or re-equilibrated at 350 to 475 °C and 1.8 to 3.6 kbar, which implies a 7 to 12 km depth of vein formation and gold mineralisation. Both phase separation of a carbonic-aqueous fluid (XCO2N0.8) and the existence of an originally CO2-dominated fluid could account for the observed fluid inclusion properties and the absence of H2O-bearing inclusions in the mineralised vein. The fluid inclusion characteristics, combined with published geological and isotopic information, indicate a deep-seated source for CO2 that could be mantle, magmatic or metamorphic in origin. We suggest that the likely sources are fluid produced by the 2.07 Ga-old charnockites that occur in the region and/or the coeval high grade metamorphism that is widespread in the Guiana Shield |
publishDate |
2010 |
dc.date.issued.fl_str_mv |
2010 |
dc.date.accessioned.fl_str_mv |
2013-12-19T16:32:42Z |
dc.date.available.fl_str_mv |
2013-12-19T16:32:42Z |
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info:eu-repo/semantics/publishedVersion |
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info:eu-repo/semantics/article |
format |
article |
status_str |
publishedVersion |
dc.identifier.citation.fl_str_mv |
KLEIN, Evandro Luiz; FUZIKAWA, Kazuo. Origin of the CO2-only fluid inclusions in the Palaeoproterozoic Carará vein-quartz gold deposit, Ipitinga Auriferous District, SE-Guiana Shield, Brazil: Implications for orogenic gold mineralisation. Ore Geology Reviews, Amsterdam, v.37, n.1, p.31-40, 2010. |
dc.identifier.uri.fl_str_mv |
https://rigeo.cprm.gov.br/handle/doc/570 |
dc.identifier.issn.none.fl_str_mv |
01691368 |
identifier_str_mv |
KLEIN, Evandro Luiz; FUZIKAWA, Kazuo. Origin of the CO2-only fluid inclusions in the Palaeoproterozoic Carará vein-quartz gold deposit, Ipitinga Auriferous District, SE-Guiana Shield, Brazil: Implications for orogenic gold mineralisation. Ore Geology Reviews, Amsterdam, v.37, n.1, p.31-40, 2010. 01691368 |
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https://rigeo.cprm.gov.br/handle/doc/570 |
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Elsevier |
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