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已通过相平衡实验、高温溶液的测热、热力学计算对共生尖晶石与单斜辉石之间Cr和Al的分配以及尖晶石-单斜辉石-石榴石平衡对Cr/Al比值的相关性进行了研究.交换平衡:?在970K、latm下测量的纯相的焓变为-2100±500cal~·.尖晶石与单斜辉石相之间Cr-Al分配的实验结果得到了下列分配关系:?这里,X_i~j指j相八面体位置中i的原子分数率.分配对成分的依赖关系意味着,根据对称模式,尖晶石中的Al-Cr混合是非理想的,其W_(Cr-Al)~(Sp)是2700±500cal/gm.反之,单斜辉石中的铝-铬混合却接近理想混合.实测的镁铬榴石(Mg_3Cr_2Si_2O_12)稳定区以及石榴石的混合性质,连同我们的实验数据用于计算Cr/Al比值对下面这个重要反应的影响:斜方辉石+单斜辉石+尖晶石=橄榄石+石榴石直到Cr/(Cr+Al)达0.7,Cr/(Cr+Al)比值每增加0.1,尖晶石二辉橄榄岩的稳定区就可增加到约2.3kbar.计算的稳定性与O’Ne?(1981)的实验结果非常一致.这样的分配关系导致在原始二辉橄榄岩较低的Cr/Alk(～0.07)比值下,单斜辉石缓冲了尖晶石成分,并使尖晶石-石榴石的反应间距从少含或不含单斛辉石时的10kbar急剧降为富辉石“地幔岩”中的2kbar.
The distribution of Cr and Al between the coexisting spinel and clinopyroxene and the ratio of the equilibrium of spinel-clinopyroxene-garnet to the ratio of Cr to Al have been calculated through phase equilibrium experiments, thermometry of thermophilic solution and thermodynamics The exchange equilibrium is: • The enthalpy of the pure phase, measured at 970K, latm, becomes -2100 ± 500 cal- • The experimental results for the Cr-Al distribution between the spinel and the clinopyroxene phase are obtained Here, X_i ~ j refers to the atomic fractional ratio of i in the octahedral position of phase j.The distribution of the dependence on the composition means that according to the symmetry mode, the Al-Cr mixing in the spinel is not ideal, and its On the contrary, the Al-Cr mixed in clinopyroxene is close to the ideal mixture.The measured stability of the magnesia-garnet (Mg_3Cr_2Si_2O_12) and the mixture of garnet The nature, along with our experimental data, was used to calculate the effect of the Cr / Al ratio on the following important reaction: orthopyroxene + clinopyroxene + spinel = olivine + garnet up to Cr / (Cr + Al) 0.7, the stability of spinel-lherzolites increases to about 2.3 kbar for every 0.1 increase in Cr / (Cr + Al) ratio. The calculated stability is in agreement with that of O’Ne? (1981) The results are very consistent, resulting in a distribution of cristobalite buffered by spinel at a lower Cr / Alk (~ 0.07) ratio of the original lherzolite, with a spinel-garnet reaction spacing From 10 kbar with or without monosodium pyrochlore to 2 kbar in fuguite “mantle rock”.