Petrology of the Miocene volcanic rocks distributed around Utsunomiya, central Japan

Abstract

Two types of Miocene volcanic rocks are distributed in Utsunomiya, central Japan. Andesite and rhyolite are intercalated with Kazamiyamada Formation, in the lower, and Oya Formation, in the upper, respectively. The Kazamiyamada andesite was subdivided into Kasamatsu andesite and Hanzo andesite, on the basis of geochemical characteristics. Rhyolites are divided to Oya and Haguro types. The Haguro rhyolite differs from the Oya rhyolite in REE pattern.
In addition, magma genesis of these volcanic rocks will be discussed by the Sr and Nd isotope ratios.