青藏高原可可西里及芒康岩区新生代火山岩中的长石及石榴子石巨晶

用Ｘ衍射分析、探针分析等方法，对可可西里和芒康岩区透长石和石榴子巨晶进行了研究。结果表明，可可西里粗安岩及芒康粗面英安岩中透长石巨晶内部光性均一，无环带和双晶，Ｘ光束见出溶条纹，矿物边部及核部成分变化很小，属高温极低有序度结构状态的钾透长石类型；石榴子石巨晶以Ａｌｍ和Ｐｙｒ为主要的二种端元组分，其结晶深度大约相当于中地壳。

Features of Megacryst on Cenozoic Volcanic Rocks from Hoh Xil and Mangkang Lithodistricts,Qinghai-Tibet Plateau

The results of the studies on the snidine and garnet megacryst from Hoh Xil and Mangkangby means of x-diffraction and probe analysis suggest that sanidine megacryst in trachyandesite andtrachydacite lithodistricts is optical homogeneous.There is not zonal texture and twin crystal.The x-ray diffractometry result indicates that there is not exsolution texture in the megacrysts.especially,chemical composltion of the megacrysts is homogeneous from the outer part to the inner part.Theyare very low in orderin8 degree and belong to K-sanidine,indicating a high rock-forming temperature.Garnet megacryst mainly consists of Alm and Pyr.Its crystallization depth resembles the depth ofmiddle crust;