| Abstract |
Yamagata prefecture, located in the northeast of Japan, has many Quaternary volcanoes with high temperature hot springs and hydrothermal alteration zones. Typical Quaternary volcanoes are Funagata, Zao and Azuma in the Ou Mountains, and Chokai, Gassan, Hayama, and Hijiori in the Uetsu Mountains. Geothermal resources related to Quaternary volcanoes such as Azuma, Zao, and Hijiori areas are accompanied by high temperature hot springs above 60 oC associated with hydrothermal acidic alteration zones. Azuma and Hijiori areas are related with volcanic depression and maximum temperatures of the exploration wells are around 250 oC. And also the HDR project was conducted in Hijiori geothermal field. Furthermore, many hot springs are distributed in this district. Yamagata prefecture has about 140 hot spring areas, more than 400 hot spring sources, and the total flow rate from these hot springs is about 48,000L/min (Yamagata Pref., 2018). High temperature hot springs are distributed close to the Quaternary volcanoes and also distributed in the basins and volcano-tectonic depression in the north-south direction, which have suitable structures favorable for thermal waters reservoirs. |