Abstract
Geological, petrological and chronological studies of the Takato granite, which is exposed in the Ina district of the Ryoke belt, have been carried out. The Takato granite intruded into the Ryoke metamorphic rocks which are composed of mainly pelitic and psamitic metamorphic rocks and consits of two bodies (northern and southern bodies) in the field. The northern body mainly consists of medium grain biotite granodiorite, and biotite granite and hornblende - biotite tonalite. The southern body is composed of hornblende-biotite tonalite. Based on mineral assemblage and whole rock chemical composition, biotite granodiorite and biotite granite, which are main constituent rock types of the northern body, were formed from dissimilar magma to the southern body and southern part of the northern body. Thus, we call biotite granodiorite to granite and hornblende - biotite tonalite "Takato granodiorite" and "Takato tonalite", respectively. The Takatao granodiorite gives a Rb-Sr whole rock isochron age of 85.2±6.6 Ma with an initial Sr isotopic ratio of 0.70774±0.00017. This age indicates time of activity of the Takatao granodiorite.Activity of the Takato tonalite is older than the Takato granodiorite. An initial Sr and Nd isotopic ratios of the Takato granodiorite are in range of initial isotopic ratios of the Ryoke granite.
