喜马拉雅造山带亚东地区基性岩的变质作用与部分熔融

The Himalayan orogen was derived by the Cenozoic collision between the India and Asia continents, representing a nature laboratory for studying metamorphism, partial melting and granite genesis of continental orogen. Ultrahigh-pressure eclogite in the western Himalayan orogen recorded the time and nature for the continental collision. However, the genesis of metabasic rocks widely distributed in the central Himalayan orogen remains controversial. This applying project will conduct a field geological, petrologic, geochemical and geochronological study and phase equilibria modeling on the metabasic rocks of the Greater Himalayan Sequence in the Yadong region, central Himalaya. The aims are to identify the distribution and types of the metabasic rocks and their contact relationship with the country rocks, characteristics of partial melting, and composition, occurrence and content of leucosome, to reveal the P-T conditions, time and P-T-t path of metamorphism and partial melting of the metabasic rocks as well as anatectic reaction, anatectic degree and melt composition, to link the partial melting of the metabasic rocks to the leucogranite genesis, and to recover the protolith type, formation time and tectonic setting of the metabasic rocks. These expected results will provide important constraints for the subduction-exhumation history of the India continent, and the tectonic models of the Himalayan orogen.

喜马拉雅造山带是印度与亚洲大陆在新生代碰撞作用的产物，是研究大陆造山带变质作用、部分熔融和花岗岩成因的天然实验室。喜马拉雅造山带西段产出的超高压榴辉岩为大陆碰撞的时间和性质提供了关键性约束。但是，造山带中段广泛分布的基性变质岩的成因还存在较大争议。本申请项目拟以亚东地区大喜马拉雅系列中的基性变质岩为研究对象，在详细的野外地质调查基础上，进行系统的岩石学、地球化学、年代学和相平衡模拟研究。项目的目标是查明基性变质岩的分布、岩石类型及与围岩的接触关系，基性变质岩的部分熔融特征以及浅色体的组成、产状与含量，揭示基性变质岩变质作用和部分熔融的温度压力条件、时间和P-T-t轨迹，研究基性变质岩部分熔融方式、熔融程度和熔体成分，探讨基性变质岩部分熔融对淡色花岗岩形成的贡献，恢复基性变质岩的原岩、形成时代和构造环境，限定印度大陆俯冲-折返的演化历史，为建立喜马拉雅造山带的构造模型提供重要制约。

喜马拉雅造山带中段的高压榴辉岩（退变质榴辉岩）/基性麻粒岩不仅记录了印度大陆地壳俯冲的重要信息，而且与广泛分布的淡色花岗岩成因密切。本项目对亚东和定日地区大喜马拉雅岩系中的基性变质岩进行了系统的岩石学、地球化学、年代学和相平衡模拟研究，初步查明了基性变质岩的岩石类型、分布特征和围岩性质，揭示出基性变质岩的峰期和退变质阶段的温度、压力条件和变质作用时间，建立了P-T-t轨迹，探讨了基性变质岩的部分熔融方式和对淡色花岗岩的贡献，恢复了基性变质岩的原岩类型和形成时代，限定了印度大陆中下地壳的俯冲-折返演化历史，为新生代的喜马拉雅造山作用提供了重要制约。