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Detailed geological,chronological,mineralogical,petrological and geochemical studies have been con-ducted of the Chicheng gneissic complex in northwestern Hebei Province.The gneissic complex is com-posed mainly of tonalitic-granodioritic rocks according to O’Connor’s classification.The zircon U-Pbage of the gneissic complex is 2468_(-27)~(+33) Ma.,consistent with that of the rocks in the NorthTonalitic-granodioritic Gneiss Belt in the North China Platform.The Archean Chicheng gneissic complexis part of the belt.No significant difference in composition between early anhedral metasomatic and late semi-euhedralplagioclases suggests that the gneissic complex is not composed merely of mafic rocks replaced by felsicfluids.The REE patterns in the complex,in conjunction with major and trace elements data.show thatthe gneissic complex is the mixture of felsic magma produced by partial melting of F(?) dacitic granulite andcrystallate derived from the magma produced by 50%±partial melting of TH_2 tholeiitic granulite and40%±fractional crystallization of hornblende.
Detailed geological, chronological, mineralogical, petrological and geochemical studies have been con-ducted of the Chicheng gneissic complex in northwestern Hebei Province. The gneissic complex is com-posed mainly of tonalitic-granodioritic rocks according to O’Connor’s classification. The zircon U- Pbage of the gneissic complex is 2468 _ (- 27) ~ (+33) Ma., Consistent with that of the rocks in the North Tonalitic-granodioritic Gneiss Belt in the North China Platform. The Archean Chicheng gneissic complex is part of the belt. Significantly, difference in composition between early anhedral metasomatic and late semi-euhedralplagioclases suggests that the gneissic complex is not composed merely of mafic rocks replaced by felsicfluids. the REE patterns in the complex, in conjunction with major and trace elements data. show that the gneissic complex is the mixture of felsic magma produced by partial melting of F (?) dacitic granulite and crystal derived from the magma produced by 50% ± partial melting of TH_ 2 tholeiitic granulite and 40% ± fractional crystallization of hornblende.