紀伊半島南部，本宮および十津川地域の温泉周辺の熱水活動史

抄録

The high temperature hot springs such as in Yunomine and Tosenji and the hydrothermal alteration zones of the Hongu area are distributed in the southern part of Kii peninsula, though Quaternary volcanoes which can be their potential heat sources are not distributed in the area. This research has aimed to understand the thermal history of the area by using several dating methods.
     Thermoluminescence (TL) dating method was applied according to the distance from dykes or gushing out point of the hot springs which thought to be the center of alteration. The results show that the alteration age of Yunomine alteration zone is younger as it approaches the gushing out point of hot spring. No clear tendency was observed in other places. These results suggest that the alteration ages near Yunomine hot spring are controlled by the distance from the gushing out point. However, no clear tendency was observed at other hot springs between the alteration ages and the distance from the center of alteration when two or more activities of alteration have occurred.
     The results of the TL, Fission Track (FT) and K-Ar dating show that after the high temperature hydrothermal alteration (until tens of millions of years ago), relatively low temperature alteration (from at least hundreds of thousands of to tens of thousands of years ago) occurred in Hongu and Totsukawa area.