MINERALOGY, GEOCHEMISTRY AND GENESIS OF CLAY DEPOSITS IN BELGAUM, DHARWAD AND CHITRADURGA DISTRICTS, KARNATAKA

A dozen clay deposits occurring in the districts of Belgaum, Dharwad a nd Chitradurga of Karnataka State have been studied. In Dharwad distri ct, while the clay deposits derived from greywackes/phyllites are domi nated by kaolinite, those derived from the acid metavolcanics contain illite as the sole clay mineral. In Belgaum and Chitradurp districts t he deposits are kaolini tic, characterised by poor crystallinity and n ear absence of illite. Chemically, the clay deposits studied have rela tively high silica and low titania. The transformation of precursor ro cks to clay deposits which was brought about by insitu chemical weathe ring and subsequent reworking of the weathered products under tropical climatic conditions was accompanied by enrichment of Al, Zr and Cr an d removal of Si, Fe, Ni, Cu and Zn. Presence of relicts of nearly all the major and accessory minerals native to the precursor rocks, in all the litho-units of clay profiles is in agreement with such an interpr etation.