Perspective for elasticity of minerals in the Earth's top lower mantle

• 作者: Zhu Mao Ningyu Sun Wei Wei
• 来源期刊: 国家科学评论（英文版）
• 年，卷（期）: 2021,（4）
• 所属期刊栏目: Special Topic:Key Problems of the Deep Earth
• 页码范围: 6-8
• 页数: 3页
• 语种: 英文
• DOI: 10.1093/nsr/nwaa270

摘要

The lower mantle, ranging from 660 to 2891 km in depth, comprises the vast majority of Earth's volume.Although the Earth's lower mantle has been regarded as compositionally homogeneous in the first order and isotropic until 150-300 km above the core-mantle boundary, there is growing seismic evidence indicating a rather complex image of the top lower mantle at depths of660-1200 km (Fig.1) [1,2].Beneath northeast Asia and North America, a 1.5-2.6％ reduction in the shear-wave velocity was identified at depths of 660-800 km [1].Near the major global subduction zones at depths of 660-1200 km, the SH wave (propagation direction parallel to the vibration direction) was observed as being up to 2％ faster than the SV wave (propagation direction perpendicular to the vibration direction), showing the presence ofseismic anisotropy in the top lower mantle [2].Deciphering the formation mechanism of the low-velocity layer and the anisotropic structure requires detailed knowledge of the elasticityof minerals under relevant pressuretemperature (P-T) conditions of thelower mantle.