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

东南印度洋海脊是位于澳大利亚和南极洲之间的中洋扩张中心。由于它的地理位置，它是海底采样和研究最少的部分之一。它也是法国海洋邮轮最近采样了大量密集分布的大洋中脊扩张中心熔岩的地方，以努力在精细尺度上检查地幔的地球化学不均一性。这项研究由美国圣地亚哥州立大学和俄勒冈州立大学的科学家与法国两家主要海洋学术机构的科学家组成，对这些熔岩进行了全面的地球化学研究，以帮助了解印度洋以下的地壳以及地幔物质的转移如何影响它。研究目标是检验一个基于统计分析和理论的危险的新假说的有效性，该假说提出地幔不均质性具有双峰性，并由条纹状的化学差异表示，这有助于我们理解地幔对流和地球的化学分异。这项工作的美国部分涉及东南印度海岭玄武岩玻璃的放射性同位素(铅、钕、锶和氢)分析和微量元素地球化学分析。这些数据将被用来确定东南印度洋海脊下的条纹状铅和Hf同位素是否传播到整个地区，(2)调查活动热点附近的中欧架玄武岩熔岩同位素不均一性是否与远离活动热区的不同，以及(3)研究同位素不均一性如何与地幔源岩性和部分熔融条件的变化有关。该提案的更广泛的影响是好的，涉及与法国两大海洋学术机构的科学家进行强有力的国际合作。该项目还将帮助支持圣地亚哥州立大学由NSF资助的开放式同位素设施，并将与法国同事一起开发改进的火山玻璃溶解程序，从而为科学建设基础设施。其他影响包括本科生培训和将研究成果纳入大学生课程。

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.