High-temperature compression of ferropericlase and the effect of temperature on iron spin transition
High-temperature compression of ferropericlase and the effect of temperature on iron spin transition
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DOI：
10.1016/j.epsl.2010.07.025
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发表时间：
2010-09-01
影响因子：
5.3
通讯作者：
Ohishi, Yasuo
中科院分区：
文献类型：
--
作者：
Komabayashi, Tetsuya;Hirose, Kei;Ohishi, Yasuo
在1600-1900 K的恒温条件下，采用激光加热金刚石对顶砧装置，对成分为（Mg0.81Fe0.19）O的铁方镁石（Fp）在116 GPa的压力下进行了高温原位X射线衍射实验。还对相同的材料进行了激光退火技术的室温实验。在T = 1600-1900 K和300 K时，分别在P=63-96 GPa和45-63 GPa下观察到可以用亚铁自旋转变解释的异常晶胞体积减小，表明自旋转变压力区间随温度的升高而扩大。在T = 1600-1900 K和300 K下，观察到的自旋转变的密度变化分别约为1.6%和1.0%，表明自旋转变压力区间随温度的升高而扩大。由于自旋跃迁的影响，中下地幔Pp的热膨胀系数较大。在橄榄岩的组成，自旋转变Fp增加了0.35%的岩石密度在最低的地幔条件。计算结果表明，钙钛矿型和橄榄岩型地幔模型都可以解释PREM下地幔的密度。然而，橄榄岩下地幔模型需要较少的假设来满足PREM密度，并且更自洽。(C)2010 Elsevier B. V.保留所有权利。
High-temperature compression experiments with in situ X-ray diffraction of ferropericlase (Fp) with a composition of (Mg0.81Fe0.19)O were made in a laser-heated diamond anvil cell to pressures (P) of 116 GPa at a constant temperature (T) of 1600-1900 K. Room-temperature experiments with a laser annealing technique were also carried out on the same material. Anomalous unit-cell volume reductions that can be explained by the spin transition of ferrous iron were observed at P=63-96 GPa and 45-63 GPa at T = 1600-1900 K and 300 K, respectively, indicating that the spin transition pressure interval expands with increasing temperature. The observed density changes across this spin transition at T = 1600-1900 K and 300 K are about 1.6% and 1.0%, respectively, indicating that the spin transition pressure interval expands with increasing temperature. The thermal expansivity of Pp is large in the mid-lower mantle due to the effect of the spin transition. In a peridotitic composition, the spin transition in Fp increases the rock density by 0.35% at the lowermost mantle conditions. Calculated densities show that both perovskitic and peridotitic mantle models may explain the PREM lower mantle density. However, the peridotitic lower mantle model requires less assumption to satisfy the PREM density and is more self-consistent. (C) 2010 Elsevier B.V. All rights reserved.