摘要
本文试图通过对桂东南地区过铝花岗岩中普遍存在的堇青石研究,探讨花岗岩的形成条件和成因问题。该类花岗岩中存在两种堇青石:一种呈变晶状或不规则状聚晶出现,属于源岩的不熔残余物成因;另一种呈半自形-自形柱状单晶分散于岩石中,属岩浆结晶成因。两者常共存,后者是前者在岩浆状态下重结晶的产物。因此认为,根据堇青石的产出状态、共生矿物、成分、光学性质和晶体内部结构的差异,可以判断花岗岩熔浆的来源及其形成的深度、压力、温度条件。
The author tries to discuss the problem on the forming conditions and origin of granite through the study the cordierites that distribute widely in aluminium-oversaturated granite in southeastern Guangxi. There are two kinds of cordierites: one occurs as crystalloblastic or irregular polycrystal, which result from unmolten residues of mudstone; the other scatter as hypidiomorphic-idiomorphic columnar monocrystals in rocks, which stem from magmatic crystallization. They coexist constantly, the later is the recrystallization product of the former under magmatic state. Hence, this paper believes that in light of the mode of occurrence, paragenetic minerals, composition, optical properties and differences of internal structures of cordierites, the derivation of granitic magma and its forming depth, pressure and temperature can be judged.
