大陆俯冲带超高压变质岩部分熔融与壳幔相互作用研究进展

自20世纪80年代在大陆地壳岩石中发现柯石英和金刚石等超高压变质矿物以来,大陆深俯冲和超高压变质作用就成为了固体地球科学研究的前沿和热点领域之一。经过三十余年的研究,已经在大陆地壳的俯冲深度、深俯冲岩石变质P-T-t轨迹、俯冲地壳岩石的折返机制、深俯冲岩石的原岩性质、大陆碰撞过程中的熔/流体活动与元素活动性、俯冲隧道内部不同类型壳幔相互作用、碰撞后岩浆岩的成因、大陆碰撞造山带成矿作用等方面取得了许多重要成果。本文重点对大陆俯冲带超高压岩石部分熔融和不同类型壳幔相互作用近十年来的研究进展进行回顾和总结,并对存在的相关科学问题和未来的研究方向进行了展望。深俯冲大陆地壳的部分熔融主要出现在两个阶段:折返的初期阶段和碰撞后阶段,前者产生了碱性熔体,后者产生了钙碱性熔体。大陆俯冲带壳幔相互作用有两种类型,涉及地幔楔与两种俯冲带流体的交代反应:一是来自深俯冲陆壳的变质脱水/熔融,二是来自先前俯冲古洋壳的变质脱水/熔融。

Progresses in the Study of Partial Melting of Ultrahigh-Pressure Metamorphic Rocks and Crust-Mantle Interaction in Continental Subduction Zones

Since the findings of ultrahigh-pressure(UHP)metamorphic minerals such as coesite and diamond in continental crustal rocks in the 1980 s,the study of continental deep subduction and UHP metamorphism has been one of the frontiers and hotspots in solid earth science.After more than 30 years of studies,many important achievements have been made in following research aspects,including the depth of continental crust subduction,the metamorphic P-T-t path of deeply subducted rocks,the exhumation mechanism of subducted crustal rocks,the protolith nature of deeply subducted rocks,the melt/fluid activity and element mobility in the process of continental collision,the different types of crust-mantle interaction in subduction channels,the petrogenesis of post-collisional igneous rocks,and the metallogenesis in collisional orogens.In this paper,we have specially reviewed and summarized research progresses in the partial melting of UHP rocks and the different types of crust-mantle interaction in continental subduction zones in the past 10 years,and have prospected the existed relevant scientific questions and future directions of studies.It merits to be emphasized that partial melting of the deeply subducted continental crust mainly took place in two stages.The first partial melting occurred during the initial stage of exhumation,giving rise to alkaline melts.The second one happened in the post-collisional stage,yielding calc-alkaline melts.There are two types of crust-mantle interaction in continental subduction zones,involving metasomatic reaction of the mantle wedge with two kinds of subduction zone fluids.One was derived from metamorphic dehydration/melting of the deeply subducted continental crust and the other was originated from metamorphic dehydration/melting of the previously subducted oceanic crust.