PETROGRAPHY AND PETROCHEMISTRY OF THE ROCKS FROM IWATE VOLCANO, NORTHEASTERN JAPAN

Iwate Volcano is a composite stratovolcano consisting of two tripple cones, older and younger volcanoes, and belongs to the northern sub-zone of the Nasu volcanic zone. The calderas, which are found in this volcano, represent two types of caldera belonging to Glencoe type. All of the lavas and pyroclastics of this volcano belong to tholeiitic rock series, but rocks of calc-alkali rock series are never found. The rocks of the older volcano are generally more advance in the stage of differentiation than those of the younger volcano, which are little differentiated. The chemical compositions of these rocks are also described.