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石榴石是山西娄烦吕梁群变质岩系中广泛出现的特征矿物,赋存原岩为泥砂质和富铝的泥质岩类。对石榴石进行了电子探针成分分析及相关计算以阐明其成分与变质温度、压力间的关系。结果表明,石榴石成分的变化有一定的规律性。利用地质温度计估算变质温度和压力,结果表明,随着变质温度和压力的升高,石榴石成分中钙铝榴石、锰铝榴石的摩尔分数降低,而铁铝榴石和镁铝榴石的摩尔分数升高。这种变化规律是由于在不同的压力条件下,石榴石晶体结构中二价阳离子处于八面体配位时离子配位半径的不同引起的。
Garnet is a characteristic mineral widely appearing in the Lvliang Group metamorphic rocks in Loufan County, Shanxi Province. Preserved rocks are muddy and aluminiferous argillaceous rocks. Electron probe composition analysis and related calculations were performed on garnet to clarify the relationship between its composition and metamorphic temperature and pressure. The results show that the composition of garnet changes have a certain regularity. The geothermal thermometer was used to estimate the metamorphic temperature and pressure. The results showed that with the increase of metamorphic temperature and pressure, the molar fraction of the garnet and the almandine decreased while that of the almandine and the magallumite The mole fraction increased. This change is due to the different pressure conditions, the garnet crystal structure of divalent cations in the octahedral coordination of ions caused by the different coordination radius.