东南极Mather半岛超高温麻粒岩中的“纳米花岗岩”研究：对变质-深熔历史和初始熔体成分的制约

高级变质作用通常伴随着地壳岩石的部分熔融，熔体汲取、迁移到就位形成花岗岩的过程，导致地壳在化学成分和结构上发生分异。但是，目前对于地壳岩石的熔融机制、过程以及初始熔体成分尚缺少有效的限定。麻粒岩中的“纳米花岗岩”(即部分或完全结晶的熔体包裹体)为我们直接观察和研究地壳初始熔体提供了重要窗口。Mather半岛位于东南极茹尔群岛南缘，该地区出露的超高温麻粒岩是受多期变质事件影响的复合变质地体，其中保留有较多“纳米花岗岩”包裹体。本项目拟对“纳米花岗岩”包裹体开展精细的岩相学和地球化学研究(如主、微量元素以及H2O和CO2成分)，结合P–T轨迹构建和年代学分析，从“纳米花岗岩”的视角为研究区超高温地体的变质-熔融历史提供严格约束。本项目的实施不仅可以加深对超高温条件下地壳熔融机制和初始熔体成分的认识，而且让我们能够从源区视角讨论花岗岩的成因，进而为地壳分异和地球深部动力学过程提供重要约束。

High-grade metamorphism is usually accompanied with partial melting of the crustal rocks, and the subsequent segregation and emplacement of melts are the mechanisms that control the crustal differentiation in chemical compositions and structures. However, melting mechanisms and processes of crustal rocks, and the starting compositions of melts, are still poorly constrained. “Nanogranitoid” inclusions (i.e. partially to totally crystallized melt inclusions) within granulites provide us with a window to directly observe and investigate the pristine crustal melts. Mather Peninsula is located in the south of the Rauer islands, East Antarctica. UHT granulites cropping out in this region were considered as ploy-metamorphic terranes, which retained amounts of “nanogranitoid” inclusions. This proposed project will be focused on the petrography and geochemistry (i.e. major and trace elements, H2O and CO2) of the “nanogranitoid” inclusions. Coupled with P-T path and geochronological results, this study will provide precise constraints on the metamorphic–anatectic processes from a perspective of “nanogranitoid”. This project will not only shed light on the melting mechanisms of crustal rocks under UHT conditions and the pristine melt compositions, but also enable us to discuss the genesis of granitoids from the standpoint of magmatic source, and therefore, may provide valuable insights into the crustal differentiation and the dynamic process of the deep crust.