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

根据这项合同，PIS建议分析大约50个深海橄榄岩中的Nd同位素，以确定在相关的橄榄岩中是否也观察到了山脊玄武岩中的ND同位素组成的变化。深海橄榄岩被认为是导致大洋中脊玄武岩的熔融残留物，然而，在对西南印度洋海脊(SWIR)两段的研究中，PI显示深海橄榄岩的143ND/144Nd比MORB具有更强的放射性成因，并不像玄武岩那样跨越范围。这一令人惊讶的结果可能表明，橄榄岩并不是玄武岩的唯一来源，最有可能的是，MORB来源中存在一种熔融温度低于橄榄岩(如辉石岩)的岩性。这项研究的目的是证实和扩大这些观察结果。正常MORB的样品将来自Kane和Gibbs断裂带、Garrett FZ、Hess Deep和沿SWIR的东经17度至30度的正交展布段。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(亚速尔羽流)、印度洋东经33度至45度之间的区域(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).