Collaborative Research: An Isotopic and Trace Element Study of Links Between Source Heterogeneity and Mantle Melting Beneath the Southeast Indian Ridge

San Diego State University Foundation, San Diego CA

Investigators

Abstract

The Southeast Indian ridge is a mid-ocean spreading center that lies between Australia and Antarctica. Due to its location, it is one of the least sampled and studied parts of the ocean floor. It is also where French oceanographic cruises have recently sampled a large number of closely-spaced mid-ocean ridge spreading center lavas in an effort to examine geochemical heterogeneity of the mantle on a fine scale. This research teams US scientists from San Diego State University and Oregon State University with scientists from two major French academic oceanographic institutions to carry out a comprehensive geochemical study of these lavas to help understand the crust below the Indian Ocean and how it is affected by the transfer of mantle material. Research goals are to examine the validity of a risky, new hypothesis, based on statistical analysis and theory, which proposes that mantle heterogeneity is bimodal in character and represented by streak-like chemical differences that can help us understand mantle convection and the chemical differentiation of the Earth. The US component of the work involves the analysis of radiogenic isotopes (Pb, Nd, Sr, and Hf) and trace element geochemical analyses of Southeast Indian Ridge basalt glasses. These data will be used to determine whether the streak-like Pb and Hf isotopes beneath the Southeast Indian Ridge propagate across the area, (2) investigate whether mid-ocen ridge basalt lava isotopic heterogeneity is different in the vicinity of active hotspot areas compared with those that are far from hotspots, and (3) investigate how isotopic heterogeneity relates to changes in mantle source lithology and partial melting conditions. Broader impacts of the proposal are good and involve strong international collaboration with scientists at two major French oceanographic academic institutions. The project will also help support an NSF-funded, open, isotope facility at San Diego State University and will develop, in conjunction with French colleagues, improved volcanic glass dissolution procedures, thereby building infrastructure for science. Additional impacts include undergraduate training and incorporation of research results into college student coursework.