【摘要】 冀东迁西三屯营地区的高级变质杂岩,主要由早太古宙的三组片麻岩所组成。岩石地球化学研究表明,较早期的三屯营片麻岩为钙碱性石英闪长质岩石,除U和Th外,它不亏损不相容元素。较晚期的小关庄片麻岩和秋花峪片麻岩,分别为钙碱性石英闪长质和钙碱性英云闪长—奥长花岗质岩石,二者均发生了不相容元素的亏损。三屯营地区的岩石亏损与未亏损是源岩浆所具有的特征,可能是初始地壳形成时上地幔不均匀造成的。更多还原

【Abstract】 Archaean high-grade metamorphic complex around Santunying of Qianxi,eastern Hebei, China, is dominantly composed of three Early Archaean gneisses（Pb-Pb isochron 3 563 Ma）. The Santunying Gneiss, which is earlier in age andquartzdioritic in composition, has higher concentrations of incompatible, LREE andsiderophile elements with K₂O, Pb, Rb and Ba undepleted. The Qiuhuayu andXiaoguanzhuang Gneisses, which are younger, show a magmatic differentiationrelationship with incompatible elements depleted. They are quartz-dioritic andtonalitic-trondjhmatic respectively. It is clear that depletion and undepletion of the gneisses are not related togranulite facies metamorphism. Heterogeneity of the mantle might have occurredas early as the Early Archaean and it was this heterogeneity that produced earlierSantunying magma rich in LIL and siderophile elements, and younger Xiaoguan-zhuang-Qiuhuayu magma poor in LIL. A disturbance of LIL, however, is obvious,which is marked by the deviation of the variation of abundances of these elementsfrom the trend of variation of magmatic crystallization. This is considered to bethe result of the granulite facies metamorphism. The co-existence of undepleted and depleted gneisses in a limited area is sig-nificant for revealing the primary relationship between the lower crust and themantlle.更多还原