南大西洋中脊（13-20°S）脊玄武岩的幔源组成及其对柱-脊相互作用的指示：Sr-Nd-Pb同位素制约

The mantle component recorded in MORB is one of key questions for understanding the cycles of earth deep materials and its effects on resource and environment. The latitudinal difference in mantle component of MORB would likely relate to the mantle plume-ridge interaction. Taking into account the MORB samples collected between 13-20°S along the South Mid-Atlantic Ridge (SMAR), a segment previously never studied on mantle component, we plan to reveal the mantle component of this segment, following the step-up studies of: (1) the texture and assemblage of phenocrystal minerals; (2) incompatible elements and Sr, Nd, and Nd isotopes in phenocrystal minerals and bulk rocks; (3) discrimination of source end-members (DM, Saint Helena and Circe mantle plume, or DM, Circe and Ascension mantle plume) and calculation of their contributions in mixed mantle. Based on the above studies, we plan to link the latitudinal change in mantle component with the spread rate of the ridge segment, distribution of fault structure, distance between mantle plumes and the ridge segment, and regional geophysical field, in order to find the relationship between latitudinal change in mantle component and mantle plume-ridge interaction. This research will provide essential references for the precisely and systematically understanding of the mechanism of mantle plume-ridge interaction along the low-spread-rate SMAR in the view of chemical geodynamics.

洋中脊玄武岩(MORB)记录的幔源组成性质是地球深部物质循环及其资源、环境效应研究的核心内容之一。南大西洋MORB的幔源组成（component）的纬向差异可能与脊-柱相互作用密切相关。本项目以南大西洋中脊地幔组成研究的空白区段（13-20°S）的MORB为研究对象，在其全岩和斑晶矿物常量、不相容元素和Sr-Nd-Pb 同位素地球化学组成特征研究基础上，通过MORB的幔源组成端员（DM和Saint Helena、Circe地幔柱，或者DM和Circe、Ascension地幔柱）的定性甄别及其各自混合比例的定量估计，揭示该区段MORB的幔源组成。在此基础上，结合研究区洋脊扩张速率、断裂构造分布、地幔柱距中脊的距离和地球物理场特征，查明该区段MORB幔源组成的纬向变化与柱-脊相互作用的关系。为精细刻画、系统完善南大西洋这一具有慢速中脊扩张速率的脊-柱相互作用化学地球动力学机制提供必要参考。