Dévitrification et altération supergène d'une rhyolite (bassin du Paraná, Brésil) : mécanismes et bilans géochimiques |
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| Authors: | Marjorie Bernard Patrick Dudoignon Norberto Dani |
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| Institution: | 1. ESIP, UMR 6532 du CNRS, université de Poitiers, 40, av. du Recteur-Pineau, 86022 Poitiers cedex, France;2. Universidade Federal do Rio Grande do Sul, Instituto de Geociências, Porto Alegre, RS, Brésil |
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| Abstract: | The weathering of a rhyolitic lava flow of the Paraná Basin (Brazil) developed, on few centimeters only, simplified petrographic features. The initial meteoric fluid pass-way is marked by celadonite-to-nontronite transformation. The second step is the complete dissolution of plagioclases, and the last one is the massive precipitation of halloysite. The geochemical mass balances according to the alteration features demonstrate the progressive leaching of major and trace elements fractionated by plagioclases, glass and opaques, and the sorption of Cu>As>Sb in the halloysite matrix. To cite this article: M. Bernard et al., C. R. Geoscience 336 (2004). |
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| Keywords: | rhyolite dévitrification céladonite nontronite halloysite altération météorique éléments traces rhyolite devitrification celadonite nontronite halloysite weathering trace elements |
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