Trace Elements and Sr, Nd Isotope Compositions of Surface Sediments in the Indian Ocean: An Evaluation of Sources and Processes for Sediment Transport and Dispersal

To decipher sediment provenance, understand dispersal pattern and its controlling factors in the Indian Ocean, we have studied major and trace element abundances and isotope compositions of Sr (Sr-87/Sr-86) and Nd (epsilon(Nd)) in silicate fractions of 38 surface sediment samples collected at similar to 1.5 degrees interval from India (similar to 10 degrees N) to Antarctica (similar to 70 degrees S). The Sr-87/Sr-86 ratio and epsilon(Nd) vary from 0.70527 and 0.1 near Crozet Island to 0.77854 and -34.8 near Antarctica, respectively. Higher Sr-87/Sr-86 ratio and lower epsilon(Nd) near Antarctica indicate source of old granitic rocks, and the opposite is observed in sediments from the Central and the Southwest Indian Ridges indicating source of seafloor spreading and mid-ocean ridge hydrothermal activity. Chondrite normalized Rare Earth Elements (REEs) pattern reveals positive Europium anomaly for Central and Southwest Indian Ridge sediments, while positive Gadolinium anomaly is observed in Indian and Antarctic coastal sediments. Sediments in the Indian sector of Southern Ocean and coastal Antarctica are highly dispersed through deep, bottom, and Antarctic circumpolar currents. The epsilon(Nd) spatial map generated for the entire Indian Ocean based on compilation of present study and results from literature shows dominance of terrigenous inputs from continental erosion with minor contribution from the ridges in the Indian Ocean. The epsilon(Nd) map together with trace elements can be employed for reconnaissancefor mineral exploration associated with hydrothermal deposits. Further, comparison of detrital epsilon(Nd) with its counter phases, that is, authigenic fractions and modern seawater at the sampling sites, would enhance our knowledge of benthic exchange processes, with an implication in using Nd isotopes asa water mass circulation proxy.