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已发表的天然超镁铁岩的辉石和尖晶石分析结果的对比表明,斜方辉石的铬含量随着共存的尖晶石的铬含量的增加而增加,直到Cr、Al比值达到1为止。超过1时,由于尖晶石含铬更多,故斜方辉石的铬含量即趋于减少。假定MgCrAlSiO_6为铬斜方辉石的组分,按照辉石—橄榄石—尖晶石组合中的化学平衡,可以解释斜方辉石和尖晶石间铬分配的非线性图式。当把这种Cr分配的平衡分析结果应用到那些超镁铁质岩、而在这些岩石中平衡作用过程又研究得很好的情况下,那么将会发现与有同样Cr、Al比的共存尖晶石相比,斜方辉石中的Cr将随平衡温度的降低而减少。然而,单斜辉石Cr数据似乎遵循一种不同的模式,但是,如果对Na与未处理的全Cr之比值的影响作一些模式校正,就会出现类似于斜方辉石的抛物线型式。如果与已发表的有关Al行为的成果结合起来,辉石的Cr和Al含量就能按全岩岩石化学和物理平衡条件得到更好的理解。
Comparison of the published pyroxene and spinel results of natural ultramafic rocks shows that the chromium content of orthopyroxenes increases with increasing chromium content of the coexisting spinel until the Cr and Al ratios reach 1 . When it exceeds 1, the chromium content of orthopyroxene tends to decrease as spinel contains more chromium. Assuming that MgCrAlSiO_6 is a component of chrome orthopyroxene, the non-linear pattern of chromium distribution between orthopyroxene and spinel can be explained in terms of the chemical equilibrium in the pyroxene-olivine-spinel combination. When applying this balanced analysis of Cr distributions to those ultramafic rocks, and where the well-balanced processes are well studied in these rocks, then coexistence with the same Cr and Al ratios Compared with spar, Cr in orthopyroxene will decrease as the equilibrium temperature decreases. However, the Crosstoid Cr data seem to follow a different pattern, but parabolic patterns similar to orthopyroxenes appear if some mode correction is made of the effect of the ratio of Na to untreated full Cr. Combined with the published results on Al behavior, the Cr and Al contents of pyroxene can be better understood in terms of rock petrochemistry and physical balance conditions.