俯冲带变质流体中Ti-Nb-Ta迁移和分异的机制：大别-苏鲁超高压榴辉岩和变质脉研究

项目名称： 俯冲带变质流体中Ti-Nb-Ta迁移和分异的机制：大别-苏鲁超高压榴辉岩和变质脉研究

项目编号： No.41303015

项目类型： 青年科学基金项目

立项/批准年度： 2014

项目学科： 天文学、地球科学

项目作者： 黄建

作者单位： 中国科学技术大学

项目金额： 26万元

中文摘要： 研究俯冲带变质流体中Ti-Nb-Ta的地球化学行为能够制约大陆地壳和岛弧岩浆岩的成因。传统观点认为Ti-Nb-Ta是流体"不活动性"元素。申请人及其它近年来的研究发现（超）高压岩石中变质脉内含有大量的富集Nb-Ta的金红石（TiO2），说明在特定的情况下，俯冲带变质流体能够导致Ti-Nb-Ta的有效迁移和分异。但是，迁移和分异的机制尚存在着较大争议，争论的焦点在于俯冲带变质流体的成份、性质和流体-岩石相互作用的强度等方面。变质脉能够提供俯冲带流体活动和元素迁移的重要信息，因此本申请拟以大别-苏鲁超高压榴辉岩-变质脉体系为研究对象，结合详细的岩相学、流体/多相固体包裹体、地球化学和锆石年代学等多种手段，探讨和验证：（1）Ti-Nb-Ta的迁移和分异与俯冲带变质流体的组成和性质以及流体-岩石相互作用的关系；（2）大别-苏鲁榴辉岩中矿物组合复杂脉的形成机制和演化。

中文关键词： 超临界流体；元素迁移和分异；变质岩；变质脉；俯冲带

英文摘要： Investigation of geochemical behavior of Ti-Nb-Ta in metamorphic fluids in subduction zones can play robust constraints on the generation of continental crust and island arc magmas. Ti, Nb, and Ta have long been regarded as fluid-immobile elements during subduction-zone metamorphism. However, the findings of Nb-Ta-rich rutile (TiO2) in metamorphic veins within (ultra)-high pressure metamorphic rocks indicate that Ti-Nb-Ta may be both transportable and fractionated during flow fluid within deep regions of subduction zones. Nonetheless, the mechanism of transportation and fractionation is controversial, focusing on the composition and property of subduction-zone metamorphic fluids and the intensity of fluid-rock interaction. As veins in metamorphic rocks are able to provide important information on fluid flow and element mobility during subduction-zone metamorphism, this study will carry out a combined study of petrology, fluid/multiphase solid inclusions, geochemistry and geochronology of zircon on the system of ultra-high pressure eclogite-vein from the Dabie-Sulu orogenic belt, trying to probe into and check: (1) the effects of the composition and property of metamorphic fluids and fluid-rock interaction on the Ti-Nb-Ta mobility/fractionation; (2) the formation mechanism and evolution of polymineralic metamorph

英文关键词： Supercritical fluids；Element mobility and fractionation；Metamorphic rocks；Metamorphic veins；Subduction zones