洋壳深俯冲带中富铝相的高温高压研究

The deeply subducted oceanic crust plays key roles in the chemical differentiation, the anisotropy of the structures and the properties, and geodynamics processes etc in the Earth's interior. The physicochemical properties of the materials in the subduction zone at various depths provide basic evidences to interpret many geological problems of the subducted slab. In the process of the subducted oceanic crust with the typical mid-oceanic ridge basalts component, the Al-rich phase (the new aluminous phase NAL and aluminous phase with calcium ferrite structure CF) occur and constitute 20~25 volume % of the deeply subducted slab. In present proposal, we will investigate on the physicochemical properties of the Al-rich phases at high temperature and high pressure conditions by combining diamond anvil cell technique, synchrotron radiation characterization, Brillouin scattering and theoretical simulation etc. The anticipated results include the P-V-T equation of state, elasticity, velocity, thermodynamic parameters of the Al-rich phases, which will be applied to discuss the iron spin state, water and potassium contents effect on the hosts' properties. Our target is to provide new evidences from experimental and theoretical simulations to understand the substantial constituents and the states of the materials in the deeply subducted zone, to constrain the interpretation for the observation of the seismic tomography.

洋壳深俯冲对地球内部物质组分的分异、结构和物性的各向异性、地球动力学过程等有着至关重要的影响。而俯冲带中物质的物理化学性质随着俯冲深度的变化，是解释俯冲板片中许多基础地质问题的最基本依据。以洋中脊玄武岩为代表的洋壳在深俯冲过程中，出现了富铝相(NAL和CF)，所占的比例为20~25%。本项目拟采用金刚石压腔技术、同步辐射表征技术和布里渊散射等多种方法，结合第一性原理计算，开展富铝相的高温高压研究，以期获得两种富铝相的P-V-T状态方程、弹性系数、波速、热力学参数等，深入讨论铁的自旋态、水的含量、钾的含量等对宿主物性的影响，为更深入了解洋壳深俯冲带中物质组成及其状态提供新的实验岩石矿物地球化学依据，为地震波速测量资料进行反演建立相应的约束条件。

洋壳深俯冲对地球内部物质状态(成分和结构)、地球动力学过程有着至关重要的影响。而俯冲带中物质的物理化学性质随着俯冲深度的变化，是解释俯冲板片中许多基础地质问题的最基本依据。以洋中脊玄武岩为代表的洋壳在深俯冲过程中，出现了富铝相(NAL和CF)，所占的比例为20~25%。本项目采用金刚石压腔技术、同步辐射表征技术和布里渊散射等多种方法，结合第一性原理计算，开展富铝相和致密硅酸盐含水相phase D的高温高压研究，获得它们的状态方程、弹性系数、波速、热力学参数等，讨论铁的自旋态、水的含量等对宿主物性的影响，为地震波速测量资料进行反演建立相应的约束条件，提出太平洋俯冲带在下地幔中部地震波速不均一性可能源于下地幔俯冲带NAL、CF和phaseD中铁的自旋转变。