东疆哈尔里克变质带中石榴子石的特征

石榴子石为东疆哈尔里克变质带中的常见矿物。从外形上可分为两种 类型，一种是晶形发育较好的石榴子石，为断裂区域变质作用形成；另一种是破碎状、裂纹 发育的石榴子石，为早期热变质作用形成，呈残留状出现。二者在空间上共存。对于晶形较 好的石榴子石的化学成分研究表明，石榴子石发育生长环带，在晶体粒径与核部MnO的含量 之间存在着相关关系。其峰期MnO的含量反映了递增变质带变质温度变化的趋势。

Characteristics of Garnets from the Harlik Metamorphic Belt in Eastern Xinjiang

Garnet is often seen in the Harlik metamorphic belt. It is distinguishe d as two different types by its morphology. The one is of a better crystal shape and formed during regional metamorphism, and the other is usually broken with c racks and recognized as a residue of early stage thermal metamorphism. Both garn ets may occur sometimes in the same samples. This study mainly focuses on the co mposi tions of garnets and their variations. The composition zoning characteristic s of the garnets, in which MnO and CaO decrease and MgO and FeO increase from co re to rim, indicate that the garnet crystallization temperatures were increasing from core to rim. The microprobe analyses reveal remarkable correlation between the MnO concentration in garnet core and its grain size. This suggests that the large garnet porphyoblasts nucleated at earlier stage and lower temperature.