Mineralogical, micromorphological and geochemical evolution of the kaolin facies deposit from the Capim region (northern Brazil) D. J. L. SOUSA 1,2 , A. F. D. C. VARAJA ˜ O 1 , J. YVON 2, * AND G.M. DA COSTA 3 1 DEGEO Departamento de Geologia /EM/UFOP, Campus Morro do Cruzeiro, 35400 000 Ouro Preto, MG, Brazil, 2 Nancy Universite´ LEM Laboratoire Environnement et Mine´ralurgie /ENSG/INPL, F-54501 Vandœuvre le`s Nancy, France, and 3 DEQUI Departamento de Quimica /ICEB/UFOP, Campus Morro do Cruzeiro, 35400-000 Ouro Preto, MG, Brazil (Received 1 July 2006; revised 10 November 2006) ABSTRACT: 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 Mo¨ ssbauer 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, Mo¨ ssbauer, TEM, SEM, ferruginization, deferruginization, degradation, Capim River, Amazon, Brazil. The Capim Kaolin District (CKD), known world- wide for the high quality of its kaolin reserves, is located in the Brazilian Amazon, northern Brazil (Fig. 1), and represents 16% of Brazilian reserves, almost 60% of the production, and 63% of the beneficiated ores exported (DNPM, 2004). More than 1 M tons of ore are sold each year to the international paper-coating market. This economic importance has promoted scientific interest in Capim kaolin since the 1970s. These studies encompass both general works on geology and genesis (Krebs & Arantes, 1973; Hurst & Bo´sio, 1975; Monteiro, 1977; Murray & Partrigde, 1981) and specific works, involving mineralogical, geochemical and facies aspects (Costa & Moraes, 1992, 1998; Moraes & Costa, 1993; Moraes, 1994; Kotschoubey et al., 1996; Sousa, 2000; Barbosa, 2002; Nascimento, 2002; Santos Jr., 2002; Barbosa et al., 2004). Many authors consider the Capim kaolin to be typically sedimentary (Krebs & Arantes, 1973; * E-mail: jacques.yvon@ensg.inpl-nancy.fr DOI: 10.1180/claymin.2007.042.1.06 Clay Minerals, (2007) 42, 69–87 # 2007 The Mineralogical Society