Lateral variation of major and trace elements in the late Miocene volcanic rocks from central part of Northeast Japan.

Abstract

Abundances of major elements and five trace elements, Rb, Sr, Nb, Y and Zr were determined by X-ray fluorescence analysis for the late Miocene (8-6 Ma) volcanic rocks of the central part of Northeast Japan, Systematic zonal variation of petrological features, i.e., mafic phenocryst assemblages and rock series, as well as gradual increase in K2O, Na2O+K2O, Rb and Sr contents are rocognized in these volcanics from the Pacific Ocean side to the Japan Sea side across the arc. Similarity of across-arc variations with regard to both the petrological and geochemical features between the late Miocene volcanics and the Quaternary volcanics suggests that the mechanism of magma generation of the late Miocene is essentially similar to the Quaternary one.