Rola minerałów ciężkich w geologii i paleogeografii

Abstract

FELDSPARS AS INDICATORS OF CRYSTALLIZATION CONDITIONS OF SOME SUDETIC GRANITOIDS Summary Both X-ray and chemical analyses aiming at establishing the structural stage and crystallization temperature of potassium feldspars and of plagioclases are, among others, applied also in solution of the problems related to the genesis of granitoids. The article presents the results of the mineralogical examinations of feldspars from the granitoids Of the Strzegom-Sobótka massif, in the light of similar examinations made for two other Sudetic granitoid massifs, i.e. for the Karkonosze and the Kudowa massifs. The Karkonosze granitoids with potassium feldspars, characterized by scarcely arranged structure, have crystallized at the highest temperature, whereas the Kudowa granitois with the potassium feldspars characterized by the highest triclinic system - at the lowest temperature. As concerns the crystallization temperature and the degree of the triclinic system of feldspars, the Strzegom granitoids take an intermediate position here. It has also been demonstrated that the macrocrystals of the Strzegom granitoids, like those of the Karkonosze granitoids, are older than the feldspars in the main rock body. The structural phase of the plagioclasses seems to prove that the crystallization of the Karkonosze and the Strzegom granitoids has taken place in the zones deeper than that of the Kudowa granitoids.