俯冲带中水流体的化学性质研究进展

Advances of the Research on Chemical Features of Aqueous Fluid in Subduction Zones

俯冲带中的水在壳幔演化和物质交换中起重要作用。本文就俯冲带中水的物理化学性质、溶液中的离子缔合、混溶、主量元素与微量元素组成等方面进行了阐述。重点剖析:1)超临界态下温度压力条件的改变导致水微观结构与性质的变化,扩散系数、粘度等性质随之改变,进而对水岩反应产生影响;2)富水流体中离子缔合影响着金属配合物数量,很大程度制约流体中矿物的溶解行为;3)低Cl流体中微量元素配分模式与岛弧玄武岩类似,意味着富水贫氯碱性硅酸盐成分的流体在地幔楔元素运移中起关键作用。并展望了俯冲带中流体化学性质研究的新手段。

The aqueous fluid in subduction zone has played important role for the evolution of crust and mantle and the mass exchange. The physico-chemical properties, ion association, miscibility, and major/trace elements of the fluid in subduction-zone have been described in this paper. Some conclusions have been drawn as follows. 1） The variation of pressure and temperature under the supercritical condition resulted in the variation of microstructure, nature, diffusion coefficient and viscosity of the fluid, and then affected the water-rock interaction, 2）The ion association has influenced the amount of metal complex, which mainly constrained the solubility of minerals in fluids, 3）The similarity of trace-element patterns of the low CI fluid in subduction zone and those of the island-arc basalts implies that the H2O-rich, Cl-poor, alkali-silicate-bearing fluid is has played fundamental role for the element transportation in the mantle wedge. In addition, some prospective new research methods on the fluid in subduction zone have been discussed.