Clay Mineralogy and Trace Element Geochemistry of Subathu, Dharmsala and Siwalik Sediments in Himalayan Foothills of Northwest India

265 analyses from 108 selected samples of Subathu, Dharmsala and Siwalik sediments by X-ray diffraction, emission spectroscopy, flame spectrophotometry and gamma ray spectrography are presented in this report. Dominant clay minerals of the Subathu, Dharmsala and Siwalik sediments are respectively moderately degraded illite and chlorite; degraded illite, vermiculite and expandable mixed-layers; and montmorillonite, kaolinite and highly degraded illite/chlorite. Trace and minor elements in clays are divided into non-detrital diadochic substitutions (B, Ba, Sr, Ga, Sc, Zn, Ge and Pb) and detrital elements as diadochic impurities (Be, P, Mn, Cu, Mo, W, Zr and V). Distribution of Li, Na, K, Rb and Cs and that of U and Th seem to be related primarily to weathering in source areas. It appears that mineralogy and crystal chemistry of clay minerals have dominating influence in selective geochemical partition of trace elements.