The Water-Fe-Pressure dependent single-crystal elastic properties of wadsleyite: Implications for the seismic anisotropy in the upper Mantle Transition Zone
The Water-Fe-Pressure dependent single-crystal elastic properties of wadsleyite: Implications for the seismic anisotropy in the upper Mantle Transition Zone
复制标题
瓦兹利石的水-铁-压力依赖性单晶弹性特性：对上地幔过渡带地震各向异性的影响
DOI：
10.1016/j.epsl.2021.116955
复制
发表时间：
2021
影响因子：
5.3
通讯作者：
Lavina, Barbara
中科院分区：
文献类型：
--
作者：
Zhou, Wen-Yi;Ren, Zhiyuan;Zhang, Jin S.;Chen, Bin;Hao, Ming;Ohuchi, Tomohiro;Miyagi, Lowell;Zhang, Dongzhou;Alp, Esen E.;Lavina, Barbara
最近的地震研究表明，在俯冲板块附近的区域存在各向异性的地幔过渡带（MTZ）。瓦兹利石是上部 MTZ 的主要各向异性贡献者，因此解释这些地震观测结果需要了解单晶弹性模量 (C i j s) 和瓦兹利石变形引起的晶格择优取向 (LPO)。瓦兹利石在其晶体结构中可以含有高达 3 wt% 的水，以羟基形式存在点缺陷，然而，水含量、铁含量和压力对瓦兹利石 C i j 的综合影响仍不清楚。在本研究中，我们测量了合成水合含铁瓦兹利石（0.14 (4) wt% 水，Fe#= 9.4，Fe 3+/ΣFe= 0.3）高达 18.2 (2) GPa 的高压单晶弹性。结合前期实验数据，分离了压力、水和Fe含量对瓦兹利石C i j s和内禀弹性各向异性的影响。我们的结果表明，瓦兹利石的固有弹性各向异性随着压力、水和铁含量的增加而降低。在 15 GPa 下，水含量增加 0.1 wt% 或 Fe# 增加 1 会使硅锰矿的 V P 和 V S 各向异性分别平均降低约 1.1-1.3% 和约 0.8-1.3%。结合之前变形实验确定的LPO，我们模拟了上MTZ中由冷俯冲板块附近的次垂直地幔流和周围地幔中的次水平地幔流产生的地震各向异性。在这两种情况下，瓦兹利石的LPO导致V SV （垂直极化剪切波速度）> V SH （水平极化剪切波速度）。我们的结果表明，瓦兹利石可能是全球范围内弱各向异性 MTZ（< 1%）的原因。考虑到水降低了瓦兹利石的弹性各向异性但促进了 LPO，地震各向异性可能不是上部 MTZ 的良好水传感器。
Recent seismic studies suggested an anisotropic Mantle Transition Zone (MTZ) in areas adjacent to subducted slabs. Wadsleyite is the main anisotropy contributor in the upper MTZ, therefore the interpretation of these seismic observations requires the knowledge of single-crystal elastic moduli (C i j s) and the deformation-induced lattice preferred orientation (LPO) of wadsleyite. Wadsleyite can host up to 3 wt% water in its crystal structure as point defects in the form of hydroxyl groups, however, the combined effect of water content, Fe content, and pressure on the C i j s of wadsleyite remains unclear. In this study, we measured the high-pressure single-crystal elasticity of a synthetic hydrous Fe-bearing wadsleyite (0.14 (4) wt% water, Fe#= 9.4, Fe 3+/ΣFe= 0.3) up to 18.2 (2) GPa. In combination with previous experimental data, we separated the effects of pressure, water, and Fe contents on the C i j s and intrinsic elastic anisotropy of wadsleyite. Our results suggest that the intrinsic elastic anisotropy of wadsleyite decreases with pressure, water, and Fe contents. At 15 GPa, increasing the water content by 0.1 wt% or Fe# by 1 decreases the V P and V S anisotropy of wadsleyite by∼ 1.1-1.3%, and∼ 0.8-1.3% in average, respectively. Combining the LPO determined in previous deformation experiments, we modeled the seismic anisotropy in the upper MTZ generated by a sub-vertical mantle flow near cold subducted slabs and a sub-horizontal mantle flow in the ambient mantle. In both scenarios, the LPO of wadsleyite leads to V SV (vertically polarized shear wave velocity)> V SH (horizontally polarized shear wave velocity). Our results suggest that wadsleyite may account for a weak anisotropic MTZ (< 1%) on the global scale. Considering the fact that water decreases the elastic anisotropy but promotes LPO of wadsleyite, seismic anisotropy may not be a good water sensor in the upper MTZ.
登录
查看更多内容
影响因子：
5.3
作者：
M. Hao;Jin S. Zhang;C. Pierotti;Wencai Zhou;Dongzhou Zhang;P. Dera
通讯作者：
M. Hao;Jin S. Zhang;C. Pierotti;Wencai Zhou;Dongzhou Zhang;P. Dera
DOI：
10.1002/2017jb015339
发表时间：
2018-04
期刊：
Journal of Geophysical Research: Solid Earth
影响因子：
--
作者：
Jin S. Zhang;J. Bass;B. Schmandt
通讯作者：
Jin S. Zhang;J. Bass;B. Schmandt
影响因子：
--
作者：
M. Núñez-Valdez;P. D. Silveira;R. Wentzcovitch
通讯作者：
M. Núñez-Valdez;P. D. Silveira;R. Wentzcovitch
影响因子：
5.3
作者：
Kawakatsu, Hitoshi;Yoshioka, Shoichi
通讯作者：
Yoshioka, Shoichi
地幔深部径向各向异性的概率
影响因子：
5.3
作者：
K. Visser;J. Trampert;S. Lebedev;B. Kennett
通讯作者：
B. Kennett