Abstract: Volcanic-sedimentary claystone of hydrolysis and strong clayization of fine fragments that are erupted and are transported by air fall, and are deposited in various kinds of media. It is a weak link in the current study of sedimentology. This paper puts emphasis on the study of the geochemical features of the trace elements in volcanic-sedimentary claystone and their difference from the features of corresponding elements in granite. This paper also discusses the source magma type and chemical differentiation mechanism of the volcanic-sedimentary claystone by applying the theory of chemical differentiation of molten magma in the upper mantle asthenosphere on both sides of the subduction zone.