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 and Chitradurga of Karnataka State have been studied. ln Dharwad district, while the clay deposits derived from greywackes/phyllites are dominated by kaolinite, those derived from the acid metavolcanics contain illite as the sole clay mineral. In Belgaum and Chitradurgadistricts the deposits are kaolinitic, characterised by poor crystallinity and near absence of illite.

Chemically, the clay deposits studied have relatively high silica and low titania. The transformation of precursor rocks to clay deposits which was brought about by insitu chemical weathering and subsequent reworking of the weathered products under tropical climatic conditions was accompanied by enrichment of Al, Zr and Cr and removal of Sit 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 interpretation.