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

合作研究：MORB 源矿物学的同位素限制

• 批准号: 0241053
• 负责人: Vincent Salters
• 金额: $ 28.08万
• 依托单位: Florida State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-03-01 至 2007-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0241053&HistoricalAwards=false
• 关键词: Collaborative; Research; Isotopic; constraints; mineralogy

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).

根据该奖项，PI 提议对大约 50 个深海橄榄岩进行 Nd 同位素分析，以确定在相关橄榄岩中是否也观察到山脊玄武岩中 Nd 同位素组成的变化。深渊橄榄岩被认为是导致大洋中脊玄武岩融化的残留物，然而，在对西南印度洋中脊 (SWIR) 两段的研究中，PI 表明，深渊橄榄岩的 143Nd/144Nd 放射性比MORB 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不是玄武岩的唯一来源，并且最有可能的是，MORB 来源中存在熔化温度低于橄榄岩（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 的样本将来自 Kane 和 Gibbs 断裂带、Garrett FZ、Hess Deep 以及沿 SWIR 的东经 17 度至 30 度之间的正交扩展段。此外，还将对明显受热点影响的区域的样本进行研究：海洋学家断裂带（亚速尔群岛羽流）、印度洋东经 33 度至 45 度之间的区域（马里恩热点）。