The compositional ranges of Mn-pyroxenoids

用能谱仪分析了日本产的锰系辉石和单斜辉石。在CaSiO_3摩尔分数为10%以下，只有贫钙的才能在较高温度下稳定存在。在所研究的辉石中，FeSiO_3的摩尔组成范围变化很大，达32摩尔%。辉石在较宽的温度范围内是稳定的，其组成范围为CaSiO_3的10%~20%，Fe的30%以下。Mg)SiO_3摩尔。低温下形成的辉长岩伴生高钙质辉石，其CaSiO_3摩尔分数达35%左右。球粒陨石的组成范围很广，在CaSiO_3摩尔分数为30%~55%之间，(Fe)在20%以下。Mg)SiO_3摩尔。高温条件下，单斜辉石在20%(Fe.Mg)SiO_3摩尔。随着温度的降低，CaMnSi2O6附近出现单斜辉石，单斜辉石在CaMnSi2O6-CaMnSi2O6-CaMnSi2O6界面上呈连续分布。也就是说，在较低的温度下，辉石的稳定范围是有限的。但它可以存在于单斜辉石区域之外。

Mn-pyroxenoids and clinopyroxenes from Japan were analysed using EDS. Pyroxmangite is extant under 10 % of CaSiO_3 mole, and only Ca-poor one is stable at higher temperatures. The compositional range of FeSiO_3 mole varies widely and reaches 32 mole % among studied pyroxmangites. Rhodonite may be stable under the wide temperature range, and its compositional range exsists between 10 % and 20 % of CaSiO_3 sole and under 30 % of (Fe. Mg)SiO_3 mole. Rhodonite accompanying johannsenite formed under low temperature is high-calcian, and its CaSiO_3 mole reaches about 35 %. Bustamite has wide compositional range located within the area between 30 % and 55 % of CaSiO_3 mole and under 20 % of (Fe. Mg)SiO_3 mole. In case of high temperature, bustamite is stable in the compositional area of clinopyroxene under 20 % of (Fe. Mg)SiO_3 mole. The decreasing temperature invites the appearance of johannsenite near CaMnSi_2O_6, and the distribution of clinopyroxenes on Ca(Fe, Mg)Si_2O_6- CaMnSi_2O_6 join becomes consecutive. That is, the stability field of bustamite is limited at lower temperatures. but it is able to exist outside of clinopyroxene area.