Isotopic ages and strontium isotopic ratios of submarine rocks in the Japan Sea

Abstract

One granodiorite, two basalts and five andesites dredged from seamounts and banks in the Japan Sea were studied by means of K-Ar and Rb-Sr dating methods. The granodiorite gives a concordant age of 227m.y, while the ages of the basalts and andesites range from 4 to 22m.y. The Sr isotopic ratios (87Sr/86Sr)0 of these samples are higher than the mean for island basalts. © 1974, GEOCHEMICAL SOCIETY OF JAPAN. All rights reserved.