Badro James, Fiquet Guillaume, Guyot François, Rueff Jean-Pascal, Struzhkin Viktor V, Vankó György, Monaco Giulio
Laboratoire de Mine Université ralogie-Cristallographie de Paris, Université Paris VI, Université Paris 7, CNRS, IPGP, 4 place Jussieu, F-75252 Paris Cedex 05, France.
Science. 2003 May 2;300(5620):789-91. doi: 10.1126/science.1081311. Epub 2003 Apr 3.
We measured the spin state of iron in ferropericlase (Mg0.83Fe0.17)O at high pressure and found a high-spin to low-spin transition occurring in the 60- to 70-gigapascal pressure range, corresponding to depths of 2000 kilometers in Earth's lower mantle. This transition implies that the partition coefficient of iron between ferropericlase and magnesium silicate perovskite, the two main constituents of the lower mantle, may increase by several orders of magnitude, depleting the perovskite phase of its iron. The lower mantle may then be composed of two different layers. The upper layer would consist of a phase mixture with about equal partitioning of iron between magnesium silicate perovskite and ferropericlase, whereas the lower layer would consist of almost iron-free perovskite and iron-rich ferropericlase. This stratification is likely to have profound implications for the transport properties of Earth's lowermost mantle.
我们测量了高压下铁方镁石(Mg0.83Fe0.17)O中铁的自旋态,发现在60至70吉帕斯卡的压力范围内发生了高自旋到低自旋的转变,这对应于地球下地幔2000公里深处。这种转变意味着下地幔的两种主要成分——铁方镁石和硅酸镁钙钛矿之间的铁分配系数可能会增加几个数量级,从而耗尽钙钛矿相中的铁。下地幔可能由两个不同的层组成。上层将由硅酸镁钙钛矿和铁方镁石之间铁分配大致相等的相混合物组成,而下层将由几乎不含铁的钙钛矿和富含铁的铁方镁石组成。这种分层可能对地球最下地幔的传输特性产生深远影响。