Ocorrência, distribuição e variabilidade granulométrica da argila caulim nos pegmatitos das regiões de Equador-RN e Junco do Seridó-PB.

Abstract

The purpose of this research is to investigate the occurence, size distribuition, yield and purity of the kaolin clay in the pegmatites from the Pegmatite Province of Borborema in the regions of the Junco do Serido-PB and Equador-RN. These variables were analysed considering various size intervals obtained by wet sieving of the samples collected from pegmatites that are being explored in the region. The exploration of the kaolin from pematites proceed without a systematic mine planning and mine safety and the clay mined from these deposits are used in various national industries. The pegmatites that are being explored can be classified in to heterogeneous and homogeneous types based on mineral zoning observed in the rocks. The kaolin clay fraction was separaed from the rocks using the sieves of 200, 325, 400 and 500 mesh and the fractions retained in the sieves were quantified to generate statistical parameters through histograms, bar diagrams, and regression analysis. The data obtained was used to execute a comparative analysis between the pegmatites in regard to the yield of the clay. The pegmatites that are being explored were grouped according to geographic occurence and nature of the pegmatite to do the analysis. Recovery of the kaolin from the rocks vary according to the localization of the pegmatites. Yield of kaolin in the heterogeneous pegmatites is very high because of the presence of zones of pure feldspar which have altered to kaolin. Here the quartz and mica impurities are relatively less. In the homogeneous pegmatites where feldspar occur disseminated with quartz and mica the kaolin yield is relatively less and tend to have more impurities. The kaolin particles are very fine grained in nature and all the clay pass through the sieve of 500 mesh. Sericite and quartz occur as impurities in the clay fraction below 325 mesh. The X-ray diffraction analysis showed that the sericite and quartz content diminishes with size and in the kaolin of below 500 mesh only small traces of these impurities were observed.