抄録
The results of field and laboratory investigations, with special reference to the modal analysis of the rocks from the plutonic mass in the vicinity of Tono, are discussed., The mass is composed generally of quartz, potash feldspar, plagioclase, biotite and hornblende showing a granodioritic nature, although parts of the mass show gabbroic facies consisting essentially of pyroxene and more basic plagioclase., It is remarkable that the direction of distribution of the rock facies bears a close resemblance to the general tectonic structure in the district, indicating the possibility of correlating the tectonic movements with the igneous injection., The tectonic movements and the igneous injection are believed to have occurred in late Cretaceous time., The heterogeneity of the igneous mass probably implies that the mass was intruded as a mixture of semi-consolidated basic rocks and more fluid granitic materials., The mixing may have occurred prior to intrusion, at a time when the materials were at considerable depth.,
