脊柱后的Mg2SiO4转化及其与660公里地震断续续的关系
1Department of Geosciences, Princeton University, Princeton, New Jersey 08544, USA. sangshim@princeton.edu
Nature
|June 1, 2001
概括
660公里的地震不连续性与地球地幔的矿物相变有关. 新的现场实验证实这种转变发生在预期的深度,与地震数据保持一致.
科学领域:
- 地质物理学 地质物理学
- 矿物物理 矿物物理
- 高压地质化学 高压地质化学
背景情况:
- 660公里的地震不连续性标志着地球地幔特性发生了重大变化.
- 这种不连续性传统上归因于 (Mg,Fe) 2SiO4.4的脊柱后转化.
- 以前的现场研究表明,这种转变发生在较低的压力下,挑战其与660公里不连续性的联系.
研究的目的:
- 在高压和高温下研究Mg2SiO4的现场相变.
- 为了确定Mg2SiO4.4中后旋转过渡的精确压力-温度条件.
- 为了使实验发现与660公里不连续性的地震观测相协调.
主要方法:
- 在现场同步子X射线衍射.
- 双面激光加热在一个钻石的细胞.
- 实验研究Mg2SiO4在20至36GPa的压力下.
主要成果:
- 从-Mg2SiO4到MgSiO3-perovskite和MgO (periclase) 的相位转换在前向和反向方向都被观察到.
- 发现这种后旋转转变的压力和温度条件与660公里不连续性的地震数据一致.
- 这与之前在现场进行的多杆压力实验的发现相矛盾.
结论:
- 脊柱后的Mg2SiO4转变与660公里的地震断裂相一致.
- 高压实验技术,如激光加热的钻石杆细胞,为了解地球深层过程提供了至关重要的数据.
- 这些先进的现场方法更好地限制了地幔不连续性的精确位置和性质.
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