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Clay Minerals; March 2007; v. 42; no. 1; p. 69-87; DOI: 10.1180/claymin.2007.042.1.06
© 2007 Mineralogical Society of Great Britain and Ireland
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Mineralogical, micromorphological and geochemical evolution of the kaolin facies deposit from the Capim region (northern Brazil)

D. J. L. SOUSA1,2, A. F. D. C. VARAJÃO1, J. YVON2,* and G.M. DA COSTA3

1 DEGEO – Departamento de Geologia /EM/UFOP, Campus Morro do Cruzeiro, 35400 000 Ouro Preto, MG, Brazil,2 Nancy Université LEM – Laboratoire Environnement et Minéralurgie /ENSG/INPL, F-54501 Vandoeuvre lès Nancy, France, and3 DEQUI – Departamento de Quimica /ICEB/UFOP, Campus Morro do Cruzeiro, 35400-000 Ouro Preto, MG, Brazil

* E-mail: jacques.yvon{at}ensg.inpl-nancy.fr

(Received 1 July 2006; revised 10 November 2006)

The Capim Kaolin District (eastern Brazilian Amazon), is one of the largest kaolin deposits in the world; with the kaolin used mainly for paper coating. The kaolin developed at the expense of Cretaceous sandy-clayey sediments of the Ipixuna formation, through intense lateritization from the Mesozoic to Cenozoic times.

This work describes the morphological, mineralogical, crystallochemical and geochemical evolution of the Capim kaolin facies. Based on the profile analysis in the open pit fronts, it encompasses X-ray diffraction, thin-section optical analysis, EDS-assisted scanning electron microscopy and transmission electron microscopy, chemical analysis, infrared and Mössbauer spectroscopies.

Six facies were defined as different stages of the supergene process. Ferruginization led to a thick duricrust on the soft kaolin, which in turn evolved from sandy-clayey sediments of the Ipixuna Formation. A subsequent deferruginization event degraded the duricrust, resulting in the flint kaolin facies.

KEYWORDS: kaolinite, XRD, IR, Mössbauer, TEM, SEM, ferruginization, deferruginization, degradation, Capim River, Amazon, Brazil






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