铁酸盐矿和后矿在深层下层地幔的深处
Ziqiang Yang1, Zijun Song2, Zhongqing Wu2,3,4
1Center for High Pressure Science and Technology Advanced Research, Shanghai 201203, China.
概括
研究人员在下层地幔条件下研究了铁酸盐转化. 他们发现了新的矿和矿后阶段,对于理解地球深层内部和地震异常至关重要.
科学领域:
- 地质物理学 地质物理学
- 矿物物理 矿物物理
- 固体地球科学 固体地球科学
背景情况:
- 铁磁酸盐主导着地球的地幔 (>80%的体积).
- 解释下层地幔地震速度异常需要理解铁磁酸盐相位转换.
- 在下层地幔条件下,铁酸盐的相变化没有得到很好的解决,与MgSiO3.3不同.
研究的目的:
- 为铁磁酸盐在广泛的压力-温度 (P-T) 范围内构建可靠的转换图.
- 在下层地幔P-T条件下研究铁酸盐的相变.
- 为下层地幔的地球物理和地球化学模型提供关键数据.
主要方法:
- 在高P-T条件下,合成铁矿矿 (Pv) 和矿后矿 (PPv) 阶段从费亚矿 (Fe2SiO4) 中.
- 利用化学分析来确定合成相的组成和结构.
- 计算压缩 (VP) 和剪切 (VS) 速度作为铁酸盐相的压力函数.
主要成果:
- 获得了具有高Fe/Si比率 (1.72(3) 的铁酸盐Pv相,包含~25mol%Fe2O3.3.
- 合成了一种铁酸PPv相位稳定在95 GPa以上.
- 铁酸盐Pv和PPv的计算VP和VS曲线几乎与MgSiO3平行,并且这些相是在下层地幔条件下报告的密度最高的酸盐.
结论:
- 高铁含量和铁在55GPa以上Si位点的旋转交叉对于解释地震观测至关重要.
- 新发现的铁酸盐相为下层地幔的地质物理和地化学模型提供了必要的约束.
- 这项研究解决了关于铁酸盐在地球下层地幔的行为方面的关键不确定性.
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