冈底斯花岗岩类中的长石光性成分和结构状态的研究

沿噶尔河-雅鲁藏布江及其北岸的冈底斯山系分布着巨大的弧形花岗质岩基,向东延伸到波密、察隅地区,其范围东西长达两千余公里、南北宽几十公里到百余公里。岩带位置与印度板块和欧亚大陆板块之间的缝合线方向一致。根据迪肖和甘塞尔报道,该岩带向西经克什米尔地区延伸到巴基斯坦境内。

OPTICAL STUDIES OF THE FELDSPARS FROM GANDES GRANITIC ROCKS

Granitic rocks of different ages are extensively distributed along the Gandes Chain. They are intimately genetic related both in origin and is space. The rocks consist mainly of diorites, granodiorites and granites, with the predominance of granodiorites in this granite belt. In general, their distribution has a tendency to change rocks nature from basic to acid from south toward north. The optical properties of feldspars indicate that alkali feldspar ordering shows itself a systematical increase along this direction just as the changes of host rocks in composition of SiO2, K2O and the volatiles. The variation of An component of plagioclase is also in comply with the decreasing of CaO, FeO + Fe2O3 and MgO of the host rocks. The ordering of alkali feldspars generally can be regarded as a complex function of chemical composition of host rocks, the dimension of rock masses and the amount and component of volatiles. Among them, it is believed, the last one is most important especially for boron. Obviously the types of rocks could play an important role to the An content of plagioclases.