Geochemical Evolution of the Mantle

地幔的地球化学演化

• 批准号: 9804891
• 负责人: Stanley Hart
• 金额: $ 46.5万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-07-01 至 2002-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9804891&HistoricalAwards=false
• 关键词: Geochemical; Evolution; Mantle

9804891HartThis accomplishment-based renewal has, as its overarching goals, the understanding of the placement, genesis, evolution and lithologic nature of the several known heterogeneous mantle domains, and the dynamics of melting and melt extraction from these mantle domains. Two of these domains have yet to be adequately characterized for their osmium isotopic composition. In order to address this, osmium isotope studies will be conducted on ocean island basalts (Pitcairn and Christmas Islands) thought to be derived from the EM1 mantle domain and on refractory chromites in abyssal peridotites (MORB domain) from all of the major spreading ridge systems of the world. Several of Earth's mantle domains are thought to be a result of lithospheric recycling, yet the lithologic expression and melting dynamics of this material are not understood. These issues will be explored via two avenues. Ion microprobe studies of the Pb isotope composition and trace element signatures of mineral (phenocryst) melt inclusions from various ocean island basalts will shed light on the melting lithologies and melt transport networks involved. The second approach will utilize Th and Ra isotope data in conjunction with melt inclusion studies for a series of historic lavas from the Galapagos Islands. The apparent derivation of a number of these islands by a wide range in degree of melting from a single mantle source will allow constraints to be placed on issues of batch versus fractional melting, percolative versus focused melt transport, continuous melt re-equilibration versus escape in high velocity conduits, and homogenous source lithology versus small-scale (veined) heterogeneities.

9804891基于成就的续签作为其总体目标，是对几个已知异质地幔域的放置，创世纪，进化和岩性性质的理解，以及从这些地幔域中熔化和融化的动力学的动力学。这些域中的两个尚未适当地以其同位素组成的渗透性来表征。为了解决这个问题，将在海洋岛玄武岩（Pitcairn和圣诞节岛）上进行osmium同位素研究，被认为是源自EM1地幔结构域以及在世界上所有主要扩散岭系统中的深渊橄榄岩（Morb域）中的EM1地幔域和难治性的铬铁矿。地球的几个地幔结构域被认为是岩石圈回收的结果，但是岩性表达和该材料的融化动力学尚不清楚。这些问题将通过两种途径探讨。来自各种海洋岛玄武岩的矿物质（emocryst）融合物的PB同位素组成和痕量元件特征的离子微探针研究将阐明涉及的熔融岩性和熔体传输网络。第二种方法将利用TH和RA同位素数据与加拉帕戈斯群岛一系列历史熔岩的融化研究结合使用。从单个地幔来源熔化的程度上，许多这些岛屿的明显推导将允许在批处理与分数熔化，渗透性熔融融化的运输，连续的融化重新平衡相对于高速速度的养殖中的逃生与同质源源（同质源源）与小质量级别（VELUS Small Sceter（Veleus Small Sceter）的问题）上放置在批处理与分数熔化，渗透性融化融化的转运，连续的融化融化的问题上。