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

根据这项合同，研究所建议分析大约50个深海橄榄岩的Nd同位素，以确定是否在相关的橄榄岩中也观察到脊玄武岩中Nd同位素组成的变化。深海橄榄岩被认为是熔融的残留物，导致洋中脊玄武岩，但在对西南印度洋脊（SWIR）的两个部分的研究中，PI显示深海橄榄岩的143 Nd/144 Nd比MORB更具放射成因，并且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不是玄武岩的唯一来源，最有可能的是，在MORB源中存在熔融温度低于橄榄岩（如辉石岩）的岩性。本研究的目的是证实和扩展这些观察结果。正常MORB的样品将来自凯恩和吉布斯断裂带，加勒特FZ，赫斯深和正交扩展段之间的17度和30度E沿着SWIR。此外，还将研究明显受热点影响的地区的样品：海洋学家断裂带（亚速尔群岛羽流）、印度洋东经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).