Physical properties of Cretaceous to Paleogene granitic rocks in Japan: Part 2. A case of the southern Tohoku region.

Abstract

About 340 granitic rock samples (including 12 gabbroic rock samples) exposed in the Abukuma Mountains, southern Tohoku region, were collected and measured on their physical properties such as density, porosity, magnetic susceptibility and natural remanent magnetization (NRM). Two tectonic lines, the Futaba Fracture Zone (FFZ) and Hatakawa Fracture Zone (HFZ) trend north in the east side of the Abukuma Mountains and the Tanagura Fracture Zone trends the NNW in the west side. Therefore, the Abukuma Mountains are divided into three areas by these tectonic lines. They are the east of the Futaba Fracture Zone, between of the Futaba Fracture Zone and the Hatakawa Fracture Zone, west of the Hatakawa Fracture Zone (between of the Hatakawa Fracture Zone and the Tanagura Fracture zone) and the South Area accompanied with metamorphic rocks. Eleven gabbroic rocks from the west of the HFZ and one from the South Area were collected and measured. The measurement result was averaged for each area.