Rb-Sr isotope systematics in a phlogopite-bearing spinel lherzolite and its implications for age and origin of metasomatism in the Horoman peridotite complex, Hokkaido, Japan

Abstract

23.0±1.2 Ma was obtained by Rb-Sr method for a phlogopite-bearing spinel lherzolite from the Horoman peridotite complex in the Hidaka metamorphic belt, Hokkaido, Japan. The age is essentially identical to the oldest ages of the country metamorphic rocks reported so far in the Hidaka metamorphic belt, and may indicate the time of a metasomatic event which occurred in the wedge mantle. This metasomatic event may have occurred during uplift of this mantle fragment under mantle conditions contemporaneously with elevation of the Hidaka metamorphic belt resulting from collision between the Eurasian and North American plates.