晋北蓝晶石、十字石和红柱石的宝石矿物学特征及形成条件

Gemmological-mineralogical Features and Forming Conditions of Staurolite, Kyanite and Sillimanite from North of Shanxi Province

晋北的十字石、蓝晶石和红柱石从研究区北部的尖山至南部的何家兰表现出一定的规律性。通过矿物成分和矿物共生组合分析,利用地质温度计并结合前人的实验数据对研究区变质地层中的蓝晶石、十字石和红柱石的形成温度和压力进行估算,结合研究区的构造特征阐明其成因。结果表明,该区西川河断裂以北地区地层中的十字石和蓝晶石形成于中压条件下[p=(5.5～7)×108Pa],变质温度为520～550℃;西川河断裂以南地区地层中的红柱石形成于较高的温度(t=570～600℃)和较低的压力(低于3×108Pa)。十字石、蓝晶石和红柱石的形成与该区西川河断裂区域变质作用有关。西川河断裂控制了南北地区的变质条件,进而控制了十字石、蓝晶石和红柱石的形成条件和空间分布。

Staurolite, kyanite and sillimanite are widely distributed through the metamorphic layers in the north of Shanxi Province and their distribution presents a certain regularity from the north to the south, namely from Jianshan to Hejialan. In order to find out the forming conditions of the three minerals and further reveal their indicative significance to the metamorphic degree of the rocks involved and the interrelation between metamorphic degree and the fault of Xichuan River, EPMA and geothermometer are adopted in the research The results of the estimated calculations, along with the petrologic features, indicate that staurolite and kyanite in the north of Xichuan River are formed at the higher pressure [p=(5~7)×108 Pa] and the lower temperature (t=520~550℃), whereas sillimanite in the south is formed at the higher temperature (t=570～600℃) and the lower pressure (p<3×108 Pa). It is concluded that the regular distribution and forming conditions of staurolite, kyanite and sillimanite are closely related to the fault of Xichuan River.