High-pressure-temperature phase relations of basaltic crust under lower-mantle conditions: implications for chemical heterogeneity in the lower mantle

下地幔的化学结构仍有争议。俯冲板块的命运是回答这一争论的关键。为了约束俯冲板块的动力学，将采用申请人独创的新型高压生成技术——kawai型碳化钨多砧压力机，在压力高达50 GPa、温度为1700、2000和2300 K的条件下，确定下地幔条件下MORB的相关系。利用本项目确定的MORB体系中组成矿物的组成和比例，估算玄武岩地壳的密度和地震波速度。在此基础上，讨论了俯冲板块玄武岩碎片在地幔动力学中的作用以及地震探测玄武岩碎片的可能性。

The chemical structure of the lower mantle remains under debate. The fate of subducting slabs is a key to answering the debate. In order to constrain dynamics of subducting slabs, phase relations of MORB under lower mantle conditions will be determined at pressures up to 50 GPa and temperatures of 1700, 2000 and 2300 K by means of the applicant’s original novel high-pressure generation technology of a Kawai-type multi-anvil press with tungsten carbide anvils. Using the compositions and proportions of constituent minerals in the MORB system determined in this project, density and seismic wave velocities of basaltic crust will be estimated. Based on these investigations, the roles of basaltic fragments of subducted slabs in mantle dynamics and possibility of the seismic detection of such fragments will be discussed.