Progress in Petrology in Japan during the Last Four Decades

Abstract

Progress in petrology in Japan is reviewed here with an emphasis on the basalt problems and experimental petrology, in which the author is most interested.
KOZU, the founder of the Japanese Association of Mineralogists, Petrologists and Economic Geologists, had made a great contribution to petrology by numerous experimental studies on rocks and rock-forming minerals. He may rightly be called the father of experimental petrology in Japan. On the other hand TSUBOI has devoted much effort to the petrogenesis of igneous and metamorphic rocks.
Basalt problems have been and will be most fascinating subjects in modern petrology. It is now generally accepted that the basalt magmas are generated by the partial melting of peridotites in the upper mantle, and that the nature of the basalt magmas depends chiefly on the depth where melting occurs. For the recent advance in this field, we owe much to the ingenious works by KUNO.
Importance of pyroclastic rocks, especially pyroclastic flow deposits, has been widely recognized in the field of volcanology. Genesis of andesites, the most abundant volcanic rocks in Japan, is an important problem waiting solution by the Japanese petrologists.
Among the studies on granitic rocks KOIDE'S memoir on the Dando granodioritic intrusives is outstanding. An interesting approach to the granite controversy was made by GORAI, who proposed the “plagioclase twin method” to decide the magmatic versus metamorphic origin of granitic rocks. Recently ultramafic rocks have been studied from the view point of the upper mantle materials, and ultramafic xenoliths enclosed in basaltic rocks are expected to provide informations on the relation between the upper mantle and basalts.
By his excellent study on the Sanbagawa crystalline schists, SUZUKI had founded the basis of metamorphic petrology in the early 1930's. Based on his many studies on the metamorphic minerals, MIYASHIRO has proposed a new scheme of metamorphic belts in Japan and a new classification of metamorphic facies.
Recent advance in experimental petrology is remarkable. Some universities and institutions in Japan are now well equipped by apparata for experiments. In the field of high pressure works on silicates, AKIMOTO and his associates have made important achievements, including synthesis of ferrosilite and olivine-spinel transition.