Abstract
Omine Acid Rocks are distributed in the central mountainland of Kii peninsula and made of several hypabyssal plutons which are scattered for the stretch of about 40Km in north-south direction. The acid rocks consist mainly of leucocractic and porphyritic granitic rocks and the present outcrops are closer to the ceiling of dome-shaped pluton. They have intruded two geological epochs, Paleozoic Chichibu Group and Mesozoic Hidaka Group, and give thermal and mechanical effects to country rocks. Omine Acid Rocks have not made a large batholith exposed intermittently but several independent plutons intruded successively.
The general chemical feature of Omine Acid Rocks is characterized by SiO2-poor and K2O-rich as compared with other Shimanto granitic rocks and average Japanese granitic rocks (Aramaki, 1972). The chemical trend of the acid rocks on the diagram Q-Or-Ab is similar to that of Washinton's table rather than that of Japanese granitic rocks.
