Initiation of the Lower Cretaceous subduction in the Northeaset Japan— Petrogenesis of the Lower Cretaceous dike rocks in the southern Kitakami Mountains, Japan

Abstract

Dike rocks preceding the Early Cretaceous plutonic activity distributed in southern part of the Kitakami Mountains, northeast Japan, are petrologically investigated.The high-Sr andesites and high-Mg andesites show similar petrochemical characteristics to those of adakite except higher Cr, Ni, and Mg contents.Petrochemical investigation indicates that the high-Sr andesite and high-Mg andesite magma can be resulted from interaction of slab derived adakitic melt with overlying wedge mantle.The shoshonites are characterized by the similar petrochemical characteristics to those of adakite except higher K and Rb contents.The chemical characteristics of shoshonites can be explained by the hypothesis of partial melting of mantle peridotite assimilated by adakitic slab melt.