Geochemical Trends in the Sediments and Manganese Nodules from a Part of the Central Indian Basin

Geochemical analyses of eighteen surface sediment samples collected from an area between 1°-15° S latitudes and 73°-87° E longitudes exhibit significant variation in their chemical composition. Distribution patterns of the major and minor elements suggest a probab Ie removal of a portion of Fe, Ti, Mg and Cr along with major portions of Mn, Ni, Cu and Zn as authigenic ferro-manganese colloids to the sediments.

The rare earth elements (REE) exhibit nearly an order of magnitude enrichment in the nodules compared to the surrounding sediments. The positive Ce anomaly in the Nodules (∼0.25) is associated with negative Ce anomaly (0.04) in the host sediment indicating its oxidative scavenging preferentially by Fe-hydroxide colloidal floes incorporating into the nodules. The shale (NASC) normalised patterns and end member ratios of REE indicate middle REE(MREE) ennchment over light REE(LREE) and heavy REE(HREE) in both nodules and sediments. The preferential uptake sequence of REE in the nodules could be given as MREE>LREE>HREE.