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Title: Contrasting oxygen fugacity of I- and S-type granites from the Araçuaí orogen, SE Brazil : an approach based on opaque mineral assemblages.
Authors: Dias, Jordania Cristina dos Santos
Gonçalves, Leonardo Eustáquio da Silva
Gonçalves, Cristiane Paula de Castro
Keywords: G1 and G2 supersuites
Issue Date: 2019
Citation: DIAS, J. C. dos S.; GONÇALVES, L. E. da S.; GONÇALVES, C. P. de C. Contrasting oxygen fugacity of I- and S-type granites from the Araçuaí orogen, SE Brazil: an approach based on opaque mineral assemblages. Mineralogy and Petrology, v. 113, p. 667–686, jun. 2019. Disponível em: <>. Acesso em: 10 mar. 2020.
Abstract: This study presents mineralogical characterization of opaque assemblages from I- and S-type granites from the Araçuaí orogen, southeastern Brazil that belong respectively, to the pre- and syn-collisional stages of the orogeny. Although these granites are geochemically well-characterized, with a robust geochemical, isotopic and geochronological database, their opaque minerals have not yet been investigated, and they provide important information about the oxygen fugacity and temperature conditions of their magmas. I-type granites (G1 Supersuite) consist of biotite hornblende granites and their opaque assemblage is ilmenite + pyrite + pyrrhotite ± magnetite ± Fe-Ti oxides ± chalcopyrite. S-type rocks (G2 Supersuite) are biotite muscovite sillimanite granites with ilmenite + graphite + pyrrhotite + pyrite as opaques. Our results combined with literature data show that ranges for oxygen fugacity (fO2) are: I-type granitoids containing magnetite and free of pyrite and phyrrhotite likely crystallized under fO2 between 10−15 bars and 10–8.5 bars, whereas magnetite free rocks containing pyrite and pyrrhotite should have crystallized with fO2 higher than 10−18 bars and lower than 10−15 bars. Regarding S-type granites, they must have crystallized under fO2 lower than 10−18 bars.
ISSN: 1438-1168
Appears in Collections:DEGEO - Artigos publicados em periódicos

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