Rubidium and Potassium Contents of Geosynclinal Basalts in the Japanese Islands

Abstract

GREEN volcanics are frequently found in the Palaeozoic system of the Carboniferous and Permian in Japan. They are intercalated in sedimentary rocks of the eugeosynclinal facies laid down in the Chichibu (Honshu) geosyncline. The green volcanics in the geosyncline are mostly basaltic lava, sill and pyroclastic rocks. The presence of pillow lava implies that almost all of them were the product of submarine volcanism. We have examined the green volcanics from various parts of the Palaeozoic, and have made chemical analyses of both major and minor elements to determine their petrochemical features and to consider the environment of volcanic eruption. In this paper, we discuss the rubidium and potassium contents of lava and sill collected from western Japan, and their bearing on recent discoveries of petrochemical features of Cainozoic volcanics elsewhere^1–3.