Thermal equation of state of majoritic knorringite and its significance for continental upper mantle
Thermal equation of state of majoritic knorringite and its significance for continental upper mantle
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DOI：
10.1002/2014jb011194
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发表时间：
2014-11
期刊：
影响因子：
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通讯作者：
A. Dymshits;K. Litasov;I. Sharygin;A. Shatskiy;E. Ohtani;A. Suzuki;K. Funakoshi
中科院分区：
文献类型：
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作者：
A. Dymshits;K. Litasov;I. Sharygin;A. Shatskiy;E. Ohtani;A. Suzuki;K. Funakoshi
通过使用Kawai型多砧装置进行的原位X射线衍射实验，获得了压力至17 GPa和温度至1673 K下的镁橄榄石Mg3.19Cr1.60Si3.19O12的P-V-T状态方程（EoS）。将室温P-V数据与三阶Birch-Murnaghan EoS拟合得到等温体积模量K 0，300 = 154（4）GPa和压力导数K′ 0，300 = 5.4（1.2）。当使用所有的P-V-T数据在固定的V0 = 1549.08 Ω 3下拟合高温Birch-Murnaghan EoS时，我们发现K 0，300 = 157（2）GPa，K′0，T = 4.5（6），（K 0，T/T）P =-0.019（4）（GPa K-1），a = 3.00（14）× 10 - 5 K-1，B = 0.65（24）× 10 - 8 K-2，其中α = a + bT是体积热膨胀系数。将德拜温度固定为θ0 = 731 K，用当前数据拟合Mie‐Grüneisen‐Debye EoS，得到Grüneisen参数，γ0 = 1.34，q = 1.0（固定）。纯镁铝榴石的热弹性参数进行了估计，并与以前的数据进行了比较其他石榴石组合物。上地幔镁铝榴石中Cr2 O3的存在使P-和S-速度降低了1.6%，密度增加了1.7%（对于20 mol.%镁铝榴石端元）。结果表明，核算钾镁岭石端元的地幔石榴石声速的准确估计的重要性。
The P‐V‐T equation of state (EoS) for majoritic knorringite Mg3.19Cr1.60Si3.19O12 at pressures to 17 GPa and temperatures to 1673 K was obtained from in situ X‐ray diffraction experiments using a Kawai‐type multi‐anvil apparatus. Fitting of the room‐temperature P–V data to a third‐order Birch‐Murnaghan EoS yielded an isothermal bulk modulus, K0,300 = 154 (4) GPa, and a pressure derivative, K′0,300 = 5.4 (1.2). When fitting a high‐temperature Birch‐Murnaghan EoS using all of the P‐V‐T data at a fixed V0 = 1549.08 Å3, we find that K0,300 = 157 (2) GPa, K′0,T = 4.5 (6), (∂K0,T/∂T)P = −0.019 (4) (GPa K−1), a = 3.00 (14) × 10−5 K−1, and b = 0.65 (24) × 10−8 K−2, where α = a + bT is the volumetric thermal expansion coefficient. Fitting the Mie‐Grüneisen‐Debye EoS with the present data with a Debye temperature fixed at θ0 = 731 K yielded a Grüneisen parameter, γ0 = 1.34 at q = 1.0 (fixed). The thermoelastic parameters of pure knorringite were estimated and were compared with the previous data on other garnet compositions. The presence of Cr2O3 in pyrope garnets in the upper mantle decreases P‐ and S‐velocities by 1.6% and the density increases by 1.7% (for 20 mol.% knorringite end member) compared to pure pyrope. The results show the importance of accounting knorringite end‐member for accurate estimation of mantle garnet acoustic velocities.