Mineral characterization of kaolin associated with the Cristo Rei Pegmatite, Domingos Martins – ES (southeastern Brazil)
Mineral characterization of kaolin associated with the Cristo Rei pegmatite, Domingos Martins - ES (Southeast Region of Brazil)
Abstract
In southeastern Brazil, numerous kaolin deposits associated with weathered pegmatites are globally recognized within the Eastern Pegmatitic Province of Brazil. The Cristo Rei pegmatite, located in Domingos Martins (south-central Espírito Santo), represents a notable example of this geological setting. Beyond its scientific relevance, it constitutes a geologic feature of local socio-economic importance, exhibiting potential for the exploitation of gem minerals, clay minerals, ornamental stones, industrial minerals, and rare-earth–bearing phases. This study aimed to investigate the mineralogical and geochemical variation of clay minerals derived from the pegmatite, in order to elucidate the formation mechanisms, evolutionary processes, and geomorphological and hydrological controls governing their distribution. Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) analyses were applied to identify and characterize kaolinite, halloysite, and gibbsite. The results reveal an evolutionary gradient controlled by topography, drainage, and weathering intensity: (i) kaolinite predominates in actively drained zones, slopes, and valley bottoms; (ii) halloysite occurs in areas with high moisture and seasonal drainage; (iii) gibbsite dominates hilltops subjected to intense leaching and advanced weathering; and (iv) transitional phases occur in intermediate zones. The data confirm a typical kaolinization gradient governed by geomorphological and hydrodynamic processes. It is concluded that the Cristo Rei pegmatite represents a genetic model of hydrothermal and supergene alteration deposits, with potential for the selective exploration of clay minerals of high technological and economic value.
