Geochemical evidence of terrigenous influence in deep-sea sediments up to 8°S in the Central Indian Basin

Thirty-two representative deep-sea sediment samples have been studied from three manganese nodule-bearing environments in the Central Indian Basin: diatomaceous-radiolarian ooze-clay, pelagic brown clay and calcareous ooze. They have been analysed for major and minor elements such as Si, Al, Ca, Mg, Na, K, Fe, Mn, P, Ti, Ba, Cu, Ni, Co, V, Zn and Cr. R-mode factor analysis reveals five important sources for these elements: (1) detrital (loaded with Fe, Ti, Al, Mg, Mn, P and K), (2) combined hydrogenetic-diagenetic (Mn, Ni, Cu, Co and Fe), (3) biogenic (Si), (4) seasalts (Na and Mg) and (5) dissolution residue (Ba). Factor scores, distributional trends of detrital elements, Al, Ti and Fe concentrations and Al/Al+Fe+Mn ratios provide new geochemical evidence for the effect of the terrigenous influx from the Ganges-Brahmaputra rivers into the northern part of the basin up to 8°S which inhibits the growth of manganese nodules in this area. In contrast, incorporation of transitional metals into sediments and manganese nodules in the other two areas of the basin is governed by hydrogenetic and diagenetic processes