Geochemical evolution of pyrochlore during supergene alteration of Catalão II ore deposit

Abstract : The crystallochemical evolution of pyrochlores in the course of the meteoric alteration has been followed, with classical techniques of mineralogical investigation (optical microscopy, SEM, electron microprobe SX50 CAMECA), on drilling and trenches tallying the thick ferrallitic alteration cover in the Catalão II ore deposit (the Goiás state, Brazil). An abrupt transformation of the primary pyrochlores (pyrochlore s.s.) into secondary species of the type bario or cerio-pyrochlore has thus been observable to the pedogenetic silcrete level of depth (30–40 m). This transformation shows the characteristics of a pseudomorphose and results from the preferential washing of some cations (Na, Ca) and anions (F), partially replaced by Ba or REE and (OH).
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Submitted on : Thursday, July 22, 2010 - 11:52:58 AM
Last modification on : Friday, April 12, 2019 - 4:22:45 PM

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Erenaldo Rocha, Mohamed Nasraoui, François Soubiès, Essaïd Bilal, Pierre de Parseval. Geochemical evolution of pyrochlore during supergene alteration of Catalão II ore deposit. Comptes rendus de l’Académie des sciences. Série IIa, Sciences de la terre et des planètes, Elsevier, 2001, 332 (2), pp.91-98. ⟨10.1016/S1251-8050(00)01504-4⟩. ⟨emse-00505023⟩

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