Collaborative Research: Isotopic constraints on the mineralogy of the MORB source

根据该合同，PIs建议分析大约50个深海橄榄岩的nd同位素，以确定是否在脊玄武岩中也观察到相关橄榄岩中nd同位素组成的变化。深海橄榄岩被认为是熔化的残留物，导致了中洋脊玄武岩的形成，然而在对西南印度脊（SWIR）的两个片段的研究中，PIs表明深海橄榄岩的143Nd/144Nd比MORB更具放射性成因，并且不像玄武岩那样跨越范围。这一惊人的结果可能表明橄榄岩不是玄武岩的唯一来源，很可能在MORB源中存在比橄榄岩更低熔融温度的岩性（如辉石岩）。本研究的目的是证实和扩展这些观察结果。正常MORB的样品将来自Kane和Gibbs断裂带、Garrett FZ、Hess Deep以及沿SWIR的17°和30°E之间的正交扩展段。此外，样本将从明显受热点影响的地区进行研究：海洋学家断裂带（亚速尔群岛羽流）、印度洋在东经33度至45度之间的地区（马里恩热点）。

Under this award, the PIs propose to analyze approximately 50 abyssal peridotites for Nd-isotopes to determine whether variations in Nd-isotopic composition in ridge basalts are also observed in the associated peridotites. Abyssal peridotites are thought to be the residues of melting that lead to mid-ocean ridge basalts, however in a study on two segments of the South West Indian Ridge (SWIR) the PIs showed that the 143Nd/144Nd of abyssal peridotites are more radiogenic than MORB and do not span the range as the basalts. This surprising result may indicate that the peridotite is not the sole source of the basalts, and most likely, a lithology with a lower melting temperature than peridotite (like pyroxenite) is present in the MORB source. The purpose of this study is to confirm and extend these observations. Samples of Normal MORB will come from the Kane and Gibbs fracture zone, Garrett FZ, Hess Deep and the orthogonal spreading segment between 17 degrees and 30 degrees E along the SWIR. In addition samples will be studied from areas that are clearly influenced by hot spots: the Oceanographer fracture zone (Azores plume) the area of the Indian Ocean between 33 degrees - 45 degrees E (Marion hot spot).