丰宁变质磷矿深成变质作用及其成矿问题

丰宁变质磷矿产于华北地台北部基底变质岩系之中。含磷灰石的角闪岩类似层状矿层已被卷入基底塑性褶皱之内,并且经历了角闪岩相至角闪石麻粒岩亚相变质作用和混合岩化(局部熔融)作用。从其角闪岩类岩石含V、Ti、P、Fe元素推测磷质矿源是与基底基性岩浆岩经变质成因有关。

PLUTONIC METAMORPHISM AND ITS RELATED MINERALIZATION PROBLEMS OF FENGNING METAMORPHIC PHOSPHORITE DEPOSIT

Fengning metamorphic phosphorite deposit is situated in the northern part of North China Platform,belonging to basement of Precambrian metamorphic series. Apatite is concentrated in a schistose orientation parallel to minerals in basement rocks, as it was formed in a process of flow, migration and recrystallization.Apatite associated with mafic minerals in the basement rocks was often paragenerated with magnetite, illmenite, Ti-magnetite, V-Timagnetite. These metamorphic amphibolites containing apatite have undergone the plastic folds as a part of the basement, and suffered the regional metamorphism and migmatization. The phosphorite material may be derived from the metabasic volcanic layers and matabasic intrusions. According to the results of chemical analyses,the authors designed a SIL-ALM-ALK-CFM diagram (Fig. 3) for comparison between magmatic and metamorphic rocks, and hence discussed some problems of the plutonic metamorphism and anatexis, and their evolutinonal tendency. Basing on the equilibrium and nonequilibrium states, the diagrams of metamorphic facies (Fig.6 and 7)is made by using Morey-Schreinmaker's method for revealing the evolutional tendency and genetic process of the plutonic metamorphism in this area.