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

东南印度洋脊是位于澳大利亚和南极洲之间的大洋中部扩张中心。 由于其位置，它是海底采样和研究最少的部分之一。 法国海洋学考察队最近也在这里对大量密集分布的洋中脊扩张中心熔岩进行了取样，以精细地考察地幔的地球化学异质性。 这项研究由来自圣地亚哥州立大学和俄勒冈州州立大学的美国科学家与来自法国两大学术海洋学机构的科学家组成，对这些熔岩进行全面的地球化学研究，以帮助了解印度洋下方的地壳以及地幔物质转移对地壳的影响。 研究目标是检验一个基于统计分析和理论的风险性新假设的有效性，该假设提出地幔异质性具有双峰特征，并以条纹状化学差异为代表，可以帮助我们了解地幔对流和地球的化学分异。 美国部分的工作涉及放射性同位素（铅，钕，锶，铪）和微量元素地球化学分析的东南印度洋脊玄武岩玻璃的分析。 这些数据将被用来确定是否条纹状的Pb和Hf同位素东南印度洋海岭下传播整个地区，（2）调查是否在活跃的热点地区附近的中奥世脊玄武岩熔岩同位素不均匀性与那些远离热点地区相比，是不同的，（3）调查同位素不均匀性如何与地幔源岩性和部分熔融条件的变化。该提案的广泛影响是好的，涉及与法国两个主要海洋学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的一个由国家科学基金会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，从而建立科学基础设施。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.