Abstract Granitic rocks occupy nearly 30% of the ground surface of Japan (Geological Survey of Japan 1982) and are mainly Mesozoic and Cenozoic in age (Fig. 4.1). Palaeozoic granites do exist, but outcrops are sparse and mostly con?ned to geological fragments rather than large granitic provinces. Many Japanese granites belong within the Late Mesozoic granitic superprovince of the NW Paci?c rim, continuing northeastwards from Japan to Sikhote Alin and Chukotka and southwestwards to the Korean Peninsula and Southern Coastal China (Fig. 4.1). As part of the ’Late Mesozoic Circum-Pacific Ring of Fire’, these Asian granites provide a mirror image of the Canadian Cordillera, Sierra Nevada and Peninsular Range granitic provinces of western North America.