Sn-polymetallic greisen-type deposits associated with late-stage rapakivi granites, Brazil: fluid inclusion and stable isotope characteristics

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dc.contributor.authorBettencourt, J. S.
dc.contributor.authorLeite, W. B.
dc.contributor.authorGoraieb, C. L.
dc.contributor.authorSparrenberger, I
dc.contributor.authorBello, RMS
dc.contributor.authorPayolla, B. L.
dc.contributor.institutionUniversidade de São Paulo (USP)
dc.contributor.institutionUniversidade Estadual Paulista (Unesp)
dc.contributor.institutionInst Pesquisas Tecnol
dc.contributor.institutionEletronorte SA
dc.date.accessioned2014-05-20T15:29:07Z
dc.date.available2014-05-20T15:29:07Z
dc.date.issued2005-03-01
dc.description.abstractTin-polymetallic greisen-type deposits in the Itu Rapakivi Province and Rondonia Tin Province, Brazil are associated with late-stage rapakivi fluorine-rich peraluminous alkali-feldspar granites. These granites contain topaz and/or muscovite or zinnwaldite and have geochemical characteristics comparable to the low-P sub-type topaz-bearing granites. Stockworks and veins are common in Oriente Novo (Rondonia Tin Province) and Correas (Itu Rapakivi Province) deposits, but in the Santa Barbara deposit (Rondonia Tin Province) a preserved cupola with associated bed-like greisen is predominant. The contrasting mineralization styles reflect different depths of formation, spatial relationship to tin granites, and different wall rock/fluid proportions. The deposits contain a similar rare-metal suite that includes Sri (+/-W, +/-Ta, +/-Nb), and base-metal suite (Zn-Cu-Pb) is present only in Correas deposit. The early fluid inclusions of the Correas and Oriente Novo deposits are (1) low to moderate-salinity (0-19 wt.% NaCl eq.) CO2-bearing aqueous fluids homogenizing at 245-450 degreesC, and (2) aqueous solutions with low CO2, low to moderate salinity (0-14 wt.% NaCl eq.), which homogenize between 100 and 340 T. In the Santa Barbara deposit, the early inclusions are represented by (1) low-salinity (5-12 wt.% NaCl eq.) aqueous fluids with variable CO2 contents, homogenizing at 340 to 390 T, and (2) low-salinity (0-3 wt.% NaCl eq.) aqueous fluid inclusions, which homogenize at 320380 degreesC. Cassiterite, wolframite, columbite-tantalite, scheelite, and sulfide assemblages accompany these fluids. The late fluid in the Oriente Novo and Correas deposit was a low-salinity (0-6 wt.% NaCl eq.) CO2-free aqueous solution, which homogenizes at (100-260 degreesC) and characterizes the sulfide fluorite-sericite association in the Correas deposit. The late fluid in the Santa Barbara deposit has lower salinity (0-3 wt.% NaCl eq.) and characterizes the late-barren-quartz, muscovite and kaolinite veins. Oxygen isotope thermometry coupled with fluid inclusion data suggest hydrothermal activity at 240-450 degreesC, and 1,0-2.6 kbar fluid pressure at Correas and Oriente Novo. The hydrogen isotope composition of breccia-greisen, stockwork, and vein fluids (delta(18)O quartz from 9.9parts per thousand to 10.9parts per thousand, deltaDH(2)O from 4.13parts per thousand to 6.95parts per thousand) is consistent with a fluid that was in equilibrium with granite at temperatures from 450 to 240 degreesC. In the Santa Barbara deposit, the inferred temperatures for quartz-pods and bed-like greisens are much higher (570 and 500 degreesC, respectively), and that for the cassiterite-quartz-veins is 415 degreesC. The oxygen and hydrogen isotope composition of greisen and quartz-pods fluids (delta(18)O(qtz-H2O)=5.5-6.1parts per thousand) indicate that the fluid equilibrated with the albite granite, consistent with a magmatic origin. The values for mica (delta(18)O(mica-H2O)=33-9.8parts per thousand) suggest mixing with meteoric water. Late muscovite veins (delta(18)O(qtz-H2O)=-6.4parts per thousand) and late quartz (delta(18)O(mica-H2O)=-3.8parts per thousand) indicate involvement of a meteoric fluid. Overall, the stable isotope and fluid inclusion data imply three fluid types: (1) an early orthomagmatic fluid, which equilibrated with granite; (2) a mixed orthomagmatic-meteoric fluid; and (3) a late hydrothermal meteoric fluid. The first two were responsible for cassiterite, wolframite, and minor coluChange in the redox conditions related to mixing-of magmatic and meteoric fluids favored important sulfide mineralization in the Correas deposit. (C) 2004 Elsevier B.V. All rights reserved.en
dc.description.affiliationUniv São Paulo, Inst Geociencias, São Paulo, Brazil
dc.description.affiliationUniv Estadual Paulista, Inst Geociencias & Ciências Exatas, BR-01405 São Paulo, Brazil
dc.description.affiliationInst Pesquisas Tecnol, São Paulo, Brazil
dc.description.affiliationEletronorte SA, Brasilia, DF, Brazil
dc.description.affiliationUnespUniv Estadual Paulista, Inst Geociencias & Ciências Exatas, BR-01405 São Paulo, Brazil
dc.format.extent363-386
dc.identifierhttp://dx.doi.org/10.1016/j.lithos.2004.03.060
dc.identifier.citationLithos. Amsterdam: Elsevier B.V., v. 80, n. 1-4, p. 363-386, 2005.
dc.identifier.doi10.1016/j.lithos.2004.03.060
dc.identifier.issn0024-4937
dc.identifier.urihttp://hdl.handle.net/11449/38779
dc.identifier.wosWOS:000227130100020
dc.language.isoeng
dc.publisherElsevier B.V.
dc.relation.ispartofLithos
dc.relation.ispartofjcr3.857
dc.relation.ispartofsjr2,670
dc.rights.accessRightsAcesso restrito
dc.sourceWeb of Science
dc.subjectrapakivi granitept
dc.subjectgreisen depositspt
dc.subjectfluid inclusionspt
dc.subjectstable isotopespt
dc.subjectBrazilpt
dc.titleSn-polymetallic greisen-type deposits associated with late-stage rapakivi granites, Brazil: fluid inclusion and stable isotope characteristicsen
dc.typeArtigo
dcterms.licensehttp://www.elsevier.com/about/open-access/open-access-policies/article-posting-policy
dcterms.rightsHolderElsevier B.V.

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