1954 Volume 60 Issue 705 Pages 241-254
Granitic rocks distributed contiguously in the Kitakami-cetral metamorphic zone are divided, petrographically as well as structurally, into three main masses, -Higami, Takekoma, and Hirota., The present part (I) deals primarily with the granite-tectonics of these masses., A characteristic flow structure (foliation and lineation) is observed in each granite mass., It is of particular interest that all lineations observed in anyone of the granite-masses are nearly consistent in direction and in plunge, representing the intrusion-axis of the mass., The directions of plunge of the axes of the three granite-masses, however, are conspicuously different from each other., Fabric diagrams constructed by plotting both foliations and lineations on Schmidt's nets, clearly illustrate the structural differences between these three., The results obtained from the present analyses are summarized as follows: Rock mass Lithological type Structural feature Type of structural pattern Direction of plunge Higami Normal granitic or trondjemitic Foliated and lineated moderately, but sheared (figs., 1 & 4 ; pl., 9, 3 & 4) B-tectonite type with monoclinic symmetry (fig., 5) NNW-NW Takekoma Granodioritic of so-called "Japan-type" Well foliated and lineated, but not sheared (figs., 8 & 9 ; Pl., 9, 1 & 2) Layered-B type with rhombic symmetry (fig., 10) S Hirota Quartz-monzonitic Foliated and lineated weakly (apparently massive and homogeneous)(fig., 11 and pl., 9, 5) Sub-layered-B type or massive-B type with rhombic or nearly isotropic symmetry (fig., 12) N
