高温地质过程中Mo元素及同位素的行为研究：以东太平洋10°30’N 和11°20’N洋中脊玄武岩为例

钼（Mo）及其稳定同位素被广泛用来指示沉积环境的氧化还原条件，在古地理、古海洋演化和古环境的应用研究中取得了很大成功。Mo同位素在表生过程中的变化使其对研究高温地质过程，如壳幔循环、俯冲过程等很有潜力。然而，Mo同位素在高温地质过程中的行为还并不清楚，目前仍处于数据观察与积累阶段。因此，本项目拟通过系统分析45件东太平洋洋脊10°30’N和11°20’N的新鲜大洋中脊玄武岩（MORB）样品Mo元素含量及同位素组成：（1）揭示东太平洋洋脊之下MORB地幔的Mo同位素组成及不均一性程度；（2）探究Mo同位素在地幔交代、部分熔融及结晶分异过程中是否分馏及分馏机制；（3）通过寻找Mo同位素与主、微量元素，Sr-Nd-Pb同位素的相关关系，探讨地幔不均一性的成因。本研究有助于建立Mo同位素地幔储库，为利用Mo同位素研究俯冲带过程、壳幔循环及地幔不均一性奠定基础。

Molybdenum and its stable isotopes are widely used to indicate the redox conditions of the sedimentary environment, and have achieved considerable success in the application of studying paleogeography, paleo-ocean evolution and paleo-environment. Potentially, these fractionated Mo isotope characteristics of surface materials could be used to study high temperature geological process, such as subduction and mantle recycling processes. However, the behavior of Mo isotope in high temperature geological processes is still unclear and is still in the stage of data observation and accumulation. In this case, this proposal focuses on systematic analyzing Mo elemental and isotopic compositions of 45 representative MORB samples from East Pacific Rise 10°30’N and 11°20’N using double spike technique by MC-ICP-MS in order to (1) reveal the Mo isotope composition and heterogeneity of the MORB mantle beneath the eastern Pacific Ocean; (2) explore the mechanism of Mo isotope fractionation in high temperature geological process of mantle metasomatism, partial melting and fractional crystallization; (3) study the potential correlation between Mo isotope and major and trace elements, Sr-Nd-Pb isotopes, and discuss the origin of mantle heterogeneity. This research is helpful to establish a reservoir of Mo isotope in mantle, which lays a foundation for studying the subduction zone process, crust-mantle process and mantle heterogeneity by using Mo isotope.