下地幔布里奇曼石与毛钙硅石混溶对大型剪切波低速省长期演化的动力学影响:二维数值模拟  

Influence of the miscibility of bridgmanite and davemaoite on the long-term evolution of large low shear velocity provinces:insights from 2-D numerical models

作　　者：李杨 牛笑光 刘少辉 史志东 张志刚[2,3] 李娟 赵亮[1,3] LI Yang;NIU XiaoGuang;LIU ShaoHui;SHI ZhiDong;ZHANG ZhiGang;LI Juan;ZHAO Liang(State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;CAS Key Laboratory of Earth and Planetary Physics,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院地质与地球物理研究所,岩石圈演化国家重点实验室,北京100029 [2]中国科学院地质与地球物理研究所,中国科学院地球与行星物理重点实验室,北京100029 [3]中国科学院大学地球与行星科学学院,北京100049

出　　处：《地球物理学报》2023年第10期4241-4252,共12页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(41888101);中国科学院国际合作重点项目(132A11KYSB20200019);中国科学院地质与地球物理研究所重点部署项目(IGGCAS-201904,IGGCAS-202204)联合资助。

摘　　要：布里奇曼石(bridgmanite)和毛钙硅石(davemaoite)是下地幔主要的端元矿物,是构成下地幔的重要基石.矿物物理学新的研究发现,在高温高压条件下这两种矿物可以发生混溶,因而可能改变下地幔的物理化学状态.本研究我们在二维地幔对流数值模型中以相变的方式模拟布里奇曼石和毛钙硅石混溶现象,讨论其对地幔热-化学结构(尤其是下地幔大型剪切波低速省)的长期动力学影响.模拟结果显示,布里奇曼石和毛钙硅石混溶更有利于下地幔大型剪切波低速省长期保存,并且这种稳定作用随大型剪切波低速省与周围地幔密度差减小而更加显著,而相变边界的克拉伯龙斜率则在长期演化过程中起次级作用.Bridgmanite and davemaoite are the primary minerals in the deep mantle and are important building blocks of the lower mantle.Recent studies in mineral physics have found that the miscibility of these two minerals will be increased and even become a single perovskite-structured mineral under high-temperature and high-pressure conditions,which would potentially change the physical and chemical state of the lower mantle.In this study,we counted the miscibility of bridgmanite and davemaoite in two-dimensional mantle convection numerical simulations and discussed its long-term dynamic effects on the thermal-chemical structure of the mantle,particularly on the stability of the large low-shear-wave-velocity provinces(LLSVP)in the lower mantle.Our simulation results show that the miscibility of bridgmanite and davemaoite has a positive influence on the long-term preservation of the LLSVPs in the lower mantle,and this stabilizing effect increases as the density difference between the LLSVP and the surrounding mantle decreases,while the Clapeyron slope of the phase transition plays a minor role in the long-term evolution.

关 键 词：地幔对流 大型剪切波低速省 布里奇曼石 毛钙硅石 矿物混溶 数值模拟 

分 类 号：P313[天文地球—固体地球物理学]