大陆俯冲带富钾高硅熔体与橄榄岩反应的高温高压实验研究

The subduction of continental crust and its interactions with the overriding mantle are recognized as fundamental solid Earth processes, yet the crust-mantle interaction of this system remains unclear. How crust-mantle interaction initiate, evolve and eventually terminate along the continental subduction zones is poorly understood, as constraints imposed by geological and geophysical observables are ambiguous. Here this proposal focuses on high P - T experimental studies on interaction between K-Si-rich melt and peridotite, in order to provide insight into the crust-mantle interaction along the continental subduction interface. We choose K-rich felsic melts from partial melting of the deeply subducted continental crust during its exhumation as crustal melt end-member, and choose mantle wedge peridotites including fertile and depleted ones as mantle end-member. We will study: (1) how the crust-derived melt metasomatizing the overlying mantle wedge, such as condition, process, and mechanism; (2) how the recycled continental component affecting the petrological property and geochemical constituent of the mantle wedge; and (3) how magmatic rocks responding to partial melting of the metasomatized mantle during evolution of the continental collision orogen. We hope our experimental studies in this proposal can contribute to understanding the crust-mantle interaction in the continental subduction zones.

深俯冲陆壳来源熔体对上覆岩石圈地幔楔的交代作用，是大陆碰撞造山带壳幔相互作用的重要过程，但这一关键的科学问题一直没有明确的认识。本项目拟拟选取苏鲁超高压地体折返过程中部分熔融产生的富钾高硅熔体为陆壳熔体端元，地幔楔橄榄岩(包括亏损型和富集型)为地幔端元，进行高温高压实验，模拟大陆俯冲通道中的壳幔相互作用。通过高温高压条件下熔体-橄榄岩反应的实验岩石学研究，结合恰当的矿物学和地球化学分析技术，揭示俯冲带深部富钾高硅熔/流体交代地幔的条件、过程和机制，以及再循环陆壳物质对地幔岩石的岩石学属性和地球化学组成的影响；并将反应熔体与苏鲁超高压变质带内的石岛碱性杂岩进行对比研究，认识被交代的橄榄岩部分熔融的产物与机理；解释造山带演化的不同阶段岩浆岩的响应，进而为大陆俯冲带壳幔相互作用过程与机理提供实验岩石学约束。

大陆碰撞造山带壳-幔相互作用，是理解造山带演化和大陆动力过程的关键。本项目选取苏鲁-大别超高压地体折返过程中部分熔融产生的富钾高硅熔体为陆壳熔体端元，地幔楔橄榄岩(包括亏损型和富集型)为地幔端元，进行高温高压实验研究，结合造山带天然样品的研究，确定深俯冲陆壳部分熔融的机制、过程以及初始熔体的组分特征；确定深俯冲陆壳发生部分熔融的原岩属性；确定大陆造山带碰撞后岩浆作用；确定幔源岩浆的成分和上升侵位机制；确定大陆俯冲带陆壳熔体交代地幔的条件、过程、机制和产物，进而解释大陆俯冲带壳幔相互作用和造山带演化的不同阶段岩浆岩的响应。通过上述研究，为理解大陆造山带演化和大陆俯冲带壳-幔相互作用提供关键的科学依据。