There outcrop characteristic Cretaceous bimodal volcanic rock assembl ag es in eastern Zhejiang, but their geneses have always been in dispute.This paper di scusses the Sr and Nd isotopic features of the two end members ,the basalts and the highK rhyolites, and demonstrates that basalts were derived from ric hed mantle wedge through metasomatism of fluids (or contaminatio n of components) from subducted slab, whereas rhyolites were formed by remelting of the old metamorphic basement.Low degree mixing took place between basic and felsic ma gmas, which not only resulted in important variation of Sr isotopic composition in the rhyolites,but probably also affect ed the N d isotopic composition of basalts to a certain degree,but had not evidently chan g ed their Sr isotopic compositions.