Abstract

Mixing properties of solid solutions of the post-spinel phases with a composition of CaCr₂O₄–CaAl₂O₄, CaCr₂O₄–CaFe₂O₄, MgCr₂O₄–MgAl₂O₄, and MgCr₂O₄–MgFe₂O₄ in the temperature range of 1873–2223 K and at a pressure of 18–25 GPa were studied by the semi-empirical modeling. These PT parameters were used to estimate a formation energy of impurity defects of trivalent metal ions (aluminum and iron) in isomorphic sites. The study results: (1) the studied binary solid solutions are characterized by a complete miscibility; (2) the incorporation of Fe³⁺ impurity ion into the post-spinel phases of MgCr₂O₄ and CaCr₂O₄ is less favorable in terms of energy than that of Al³⁺ ions over the entire pressure and temperature range under study. The results obtained were used to interpret compositions of the post-spinel phases forming inclusions in lower mantle diamonds.

中文翻译：

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后尖晶石相的同象特征：下地幔钻石中包裹体成分的计算机模拟

摘要

_{CaCr 2} O ₄ –CaAl ₂ O ₄、CaCr ₂ O ₄ –CaFe ₂ O ₄、MgCr ₂ O ₄ –MgAl ₂ O ₄和 MgCr ₂ O ₄组成的后尖晶石相固溶体的混合特性通过半经验模型研究了1873-2223 K温度范围和18-25 GPa压力下的-MgFe ₂ O ₄ 。这些PT参数用于估计同构位点中三价金属离子（铝和铁）的杂质缺陷的形成能。研究结果：（1）所研究的二元固溶体具有完全混溶的特点； (2)在整个研究的压力和温度范围内， Fe ^{3+杂质离子掺入MgCr} ₂ O ₄和CaCr ₂ O ₄的尖晶石后相中，在能量方面不如Al ³⁺离子有利。 。获得的结果用于解释下地幔钻石中形成夹杂物的后尖晶石相的成分。