Nature, distribution and origin of clay minerals in grain size fractions of sediments from manganese nodule field, Central Indian Ocean Basin

Abstract

DT, IR and X-ray diffraction analyses have been carried out on 3 grain size fractions (1, 1-2 and 2-4 mu m) of sediments from the Central Indian Ocean Basin. Results indicate that there are 2 smectite minerals (montmorillonite and Fe-rich montmorillonite). Montmorillonite is present in all size fractions of sediments, whereas Fe-rich montmorillonite is present only in 1 and 1-2 mu m fractions of siliceous and 1 mu m fractions of pelagic clays. Distribution of clay minerals suggests that illite, chlorite and kaolinite are the detrital products from Ganges and Brahmaputra and montmorillonite is derived from the weathering of the ridge rocks-Fe-rich montmorillonite in siliceous and pelagic clay is a result of early diagenetic processes. Size fraction studies suggest that montmorillonite tends to crystallise in 2 mu m size range