Gold-bearing iron duricrust in Central Brazil

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dc.contributor.authorde Oliveira, S. M B
dc.contributor.authorCampos, E. G. [UNESP]
dc.contributor.institutionUniversidade de São Paulo (USP)
dc.contributor.institutionUniversidade Estadual de Campinas (UNICAMP)
dc.contributor.institutionUniversidade Estadual Paulista (Unesp)
dc.date.accessioned2014-05-27T11:17:26Z
dc.date.available2014-05-27T11:17:26Z
dc.date.issued1991-11-01
dc.description.abstractIn the Cuiabá region-State of Mato Grosso, Central Brazil-primary gold mineralization is hosted by two generations of quartz veins in Precambrian metamorphic terrains of the Cuiabá Group. Gold is mined from the veins and mainly from the eluvial horizons that cover the deeply altered basement. In the lodes gold occurs as small particles (less than 1 mm) associated with pyrite and contains up to 5% Ag. Larger particles and nuggets of almost pure gold are found in the iron duricrust which caps the upper levels of the weathering profile. It is difficult to determine the average grade of this kind of deposit but some prospects in the Cuiabá region produce up to 2 g gold per ton of ore. Lateritization is responsible for both the formation of the iron crust and the concentration of gold within the regolith. Under a tropical climate, the supergene alteration of phyllites of the Cuiabá Group has led to the formation of a weathering profile consisting typically of saprolite, mottled clay zone and duricrust, from bottom to top. The duricrust is directly derived form the in situ weathering of phyllites. Geochemical balance calculations indicate that in the transition from the saprolite to the duricrust lateritization has promoted a progressive loss of Si, Al and K, and more than 500% of absolute Fe enrichment. Gold underwent a supergene evolution related to the development of the weathering profile. In the saprolite and mottled clay zone, associated with quartz and oxidized sulfides, gold dissolves as demonstrated by corrosion features at the surface of the particles. The formation of secondary gold in the duricrust is indicated by the larger size of the nuggets, their higher fineness and the close relationship between gold and the neoformed iron oxy-hydroxides. © 1991.en
dc.description.affiliationInstituto de Geociências Universidade de São Paulo, 01498 São Paulo
dc.description.affiliationInstituto de Geociências UNICAMP, 13081 Campinas
dc.description.affiliationInstituto de Geociências e Ciências Exatas UNESP, 13500 Rio Claro
dc.description.affiliationUnespInstituto de Geociências e Ciências Exatas UNESP, 13500 Rio Claro
dc.format.extent309-323
dc.identifierhttp://dx.doi.org/10.1016/0375-6742(91)90005-F
dc.identifier.citationJournal of Geochemical Exploration, v. 41, n. 3, p. 309-323, 1991.
dc.identifier.doi10.1016/0375-6742(91)90005-F
dc.identifier.issn0375-6742
dc.identifier.scopus2-s2.0-0026359454
dc.identifier.urihttp://hdl.handle.net/11449/64150
dc.language.isoeng
dc.relation.ispartofJournal of Geochemical Exploration
dc.relation.ispartofjcr2.858
dc.relation.ispartofsjr0,916
dc.rights.accessRightsAcesso restrito
dc.sourceScopus
dc.subjectGeology--Weathering
dc.subjectRock--Geochemistry
dc.subjectDuricrust Lateritization
dc.subjectGold-Bearing Iron Duricrusts
dc.subjectLateritic Gold Mineralization
dc.subjectSupergene Alteration
dc.subjectWeathering Profiles
dc.subjectGold Deposits
dc.subjectCuiaba Group
dc.subjectgold
dc.subjectiron duricrust
dc.subjectlateritization
dc.subjectmineralization
dc.subjectquartz vein
dc.subjectweathering profile
dc.subjectBrazil, Mato Grosso, Cuiaba
dc.titleGold-bearing iron duricrust in Central Brazilen
dc.typeArtigo
dcterms.licensehttp://www.elsevier.com/about/open-access/open-access-policies/article-posting-policy

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