Isotopic and geothermodynamic studies of the granitic plutons

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Strontium isotopic analysis of apatite was carried out for the Cretaceous Kamihara Tonalite, Ryoke belt, southwestern Japan. It provides direct evidence of SrI heterogeneity in the Kamihara Tonalite. The SrI heterogeneity was caused by the assimilation of high SrI country metamorphic rocks of the Ryoke belt. The original magma and the wall rocks were estimated to be mixed in the ratio 3:7 for the Tenryu area and 8:2 for the Shimoyama area. The effect of assimilation is more significant in the Tenryu area. The Kamihara Tonalite in the Shimoyama area was emplaced after the assimilation of wall metamorphic rocks to an extent of 20% and subsequent complete homogenization. These emplacements occurred under a pressure ranging from 0.15 to 0.44GPa.