苏鲁造山带超高压变质岩部分熔融过程中的Mg-Fe同位素分馏行为

大陆俯冲带超高压变质岩部分熔融行为及其地球化学效应是研究深俯冲板片地球化学分异和壳幔相互作用的核心内容之一。尽管目前在深俯冲板片的部分熔融过程、时限、机制和产物性质等方面取得了突出进展，对熔体的地球化学组成，特别是对不同温压条件下部分熔融过程中Mg-Fe同位素的分馏行为及其控制因素，仍然缺乏关键制约。针对这个重要问题，本项目计划对苏鲁威海地区的混合岩和仰口地区代表高压-超高压熔体的花岗岩脉体进行系统的岩石地球化学研究，拟通过全岩主微量元素和Sr-Nd-O同位素、矿物原位微区地球化学及年代学分析，查明熔体产物的形成时限、熔融条件、熔体组成及其控制因素。在此基础上，系统分析全岩和矿物的Mg-Fe同位素，查明高压-超高压条件下部分熔融熔体的Mg-Fe同位素组成，揭示Mg-Fe同位素分馏行为及其控制因素，结果将促进对高温Mg-Fe同位素体系的理解，深化对深俯冲板片部分熔融地球化学效应的认识。

Research on partial melting of UHP metamorphic rocks and its geochemical effects in continental subduction zones is one of the core contents in the study of geochemical differentiation of deep subduction slabs and crust-mantle interactions. Although much progress has been made in the process, time limit, mechanism and product properties of partial melting of deep subducted crust, there is still a lack of key constraints on the geochemical composition of melts, especially on the fractionation behavior and controlling factors of Mg-Fe isotopes during partial melting under different P-T conditions. To solve this important issue, this project plans to systematically study the petrogeochemistry of Weihai migmatite and Yangkou granite veins representing high pressure and ultrahigh pressure melts in the Sulu orogen. It is planned firstly to find out the formation time, melting conditions, melt compositions and control factors on partial melting products through the analysis of whole-rock major and trace elements, Sr-Nd-O isotopes, in-situ mineral geochemistry and geochronology. On this basis, we further systematically analyze the Mg-Fe isotopic compositions of whole-rocks and minerals, to find out the Mg-Fe isotopic compositions of partial melts under high pressure and ultrahigh pressure conditions, and reveal the Mg-Fe isotopic fractionation behaviors. The results will promote the understanding of high temperature Mg-Fe isotopic systems and deepen the understanding of geochemical effects of partial melting of deep subducted slabs.