下层地幔的组成和热状态来自联合3D倒置与地震断层扫描和矿物弹性
Xin Deng1, Yinhan Xu1, Shangqin Hao1,2
1Deep Space Exploration Laboratory / School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China.
概括
地球的下层地幔富含,温度和组成的变化影响地震异常. 大型低剪速省份 (LLSVPs) 更热,更密集,可能起源于早期的岩海洋.
科学领域:
- 地质物理学 地质物理学
- 矿物物理 矿物物理
- 地震学 地震学
背景情况:
- 了解地球地幔的组成和热状态对于破译行星进化至关重要.
- 下层地幔的化学和热结构,特别是大型低剪速省份 (LLSVPs),仍然受到很小的约束.
- 地震断层扫描揭示了下层地幔的显著异质性,但它们的起源 (热与组成) 是有争议的.
研究的目的:
- 为了反转地球下层地幔的3D化学组成和热状态.
- 调查大型低剪速省份 (LLSVPs) 的性质和起源.
- 为了区分上层和下层地幔地震速度异常的原因.
主要方法:
- 利用地震断层扫描数据和矿物弹性数据.
- 采用马尔科夫链蒙特卡洛框架进行反转.
- 分析了温度和组成的横向和深度依赖的变化.
主要成果:
- 下层地幔是富含的,Mg/Si比率 (~1.16) 比上层地幔低.
- 侧面温度变化遵循高斯分布在上层下层地幔,但不是在最下层地幔.
- 速度异质性主要是上下地幔的热性,以及最下层地幔的组成/相位变化.
- LLSVPs表现出更高的温度 (~500 K),在底部的密度,以及更高的布里格曼和铁含量,支持基底岩海洋起源.
结论:
- 下层地幔的组成与上层地幔不同.
- 下层地幔的地震异常有不同的起源,取决于深度.
- LLSVPs被解释为早期地球基底岩海洋的残余,其特点是独特的热和组成特性.
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