Petrogenesis and Evolution of Mesozoic Complexes from Southern Taihang Orogen

Pingshun-FuShan-WuAn-HongShan complex mainly consists of olivine-gabbro-diabase, hornblende diorite, diorite, monzodiorite, syenite and granite, which have similar geochemical properties. The content of CaO, FeO, MgO, TiO and SiO₂ are in linear positive correlation. The composite pluton is enriched in lithophylic elements (such as Sr, Ba, K) and LREE, but is depleted in high field strength elements (such as Nb, Ta, Ti) and HREE, and there is a weak positive Eu anomaly. The value of epsilon Nd(t) varies from -12.3 to -16.9 in FuShan complex, with that ofⅠSr ranges from 0.7056 to 0.7071; the value of epsilon Nd(t) varies from -13.8 to -18 in WuAn complex, and the value ofⅠSr is between 0.7059~0.7076. By contrast, the values of ε_Nd (-8.2~-11) in HongShan complex is obviously higher and relatively more homogeneous than that in FuShan-WuAn complex, and the value of I_Sr (0.705 2~0.710 2) has a greater variety. Pb isotope ratio of PingShui complex is relatively higher, the values of (²⁰⁶Pb/²⁰⁴Pb)_I, (²⁰⁷Pb/²⁰⁴Pb)_I and (²⁰⁸Pb/²⁰⁴Pb)_i are respectively 17.859~18.474, 15.429~15.612, 37.374~38.641, while those of FuShan complex (16.92~17.3, 15.32~15.42, 37.16~37.63), WuAn complex (16.63~17.4, 15.28~15.44, 36.78~37.3), and HongShan complex (17.28~17.74, 15.40~15.48, 37.01~38.12) change continuously. Pingshun-Fushan-Wuan complexes are probably the products of contemporaneous magma evolution, originated from the partial melting of EMI-enriched mantle, but experienced different degrees of hybridization of crust materials in the rising process. Hongshan complex also originated from the partial melting of EMI-enriched mantle, but belonged to different magmatic thermal event, and merely experienced slight hybridization of crust materials. The extensive Mesozoic Magmatic Activity of southern Taihang Mountain is probably related to the plume upwelling of Hanxing.