Petrochemical characteristics of the Mesozoic-Cenozoic volcanic rock in Huanghua basin

Based on the data from typical core sampling, combined with K Ar dating, petrochemistry ,trace elemental geochemistry and isotopic compositions of the Mesozoic Cenozoic volcanic rock in the Huanghua basin, Bohai region, the geochemical features of the volcanic rock were studied. The rocks fall into four groups: Cenozoic basalt,Mesozoic late Cretaceous basaltic trachy andesite, Mesozoic late Cretaceous trachy dacite and liparite,and Mesozoic early Triassic dacite. The distribution pattern of the main elemental abundance of late Mesozoic shows a typical bimodal.Chronologically,for the volcanic rock,the amount of SiO 2 decreases gradually,the contents of Fe 2O 3,FeO,CaO,MgO,TiO 2,P 2O 5 and MnO increase little by little.The Cenozoic basalt is derived from the asthenospheric mantle.The late Cretaceous basaltic trachy andesite is derived from the enriched lithospheric mantle.In late Cretaceous and early Palaeogene,the felsic volcanic rock may be derived from fractional melting of the crust.