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. (28th June 2019) - Subha Anand, S.
Abstract: 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 ( 87 Sr/ 86 Sr) and Nd (εNd ) in silicate fractions of 38 surface sediment samples collected at ~1.5° interval from India (~10°N) to Antarctica (~70°S). The 87 Sr/ 86 Sr ratio and ε Nd vary from 0.70527 and 0.1 near Crozet Island to 0.77854 and −34.8 near Antarctica, respectively. Higher 87 Sr/ 86 Sr ratio and lower ε 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 ε 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 ε Nd map together with trace elements can be employed for reconnaissance for mineral exploration associated with hydrothermal deposits. Further, comparison of detrital ε 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 as a water mass circulation proxy. Key Points: Sediment provenance and dispersal pattern were studied in the Indian Ocean based on Sr and Nd isotope compositions of surface sediment collected along N‐S transect (10°N–70°S) from India to Antarctica In the entire study region, the 87 Sr/ 86 Sr ratio and ε Nd vary from 0.70527 and 0.10 near Crozet Island to 0.77854 and − 34.8 near Antarctic coast, respectively The ε Nd surface plot generated for the entire Indian Ocean shows dominance of terrigenous inputs from continental erosion with minor contribution from Indian Ocean ridges