抄録
Thermoluminescence of quartz in pyroclastic rocks of the Neogene to the Quaternary in the Minase geothermal area, Akita prefecture, was studied. This area is mainly composed of the Doroyu, Minasegawa, Sanzugawa Formations and the Kurikomayama volcanics in ascending order.. Quartz was picked out from nine boreholes cores.
There is no clear relation between vertical variations of thermoluminescence (TL) intensity and the stratigraphical units. The TL intensity decreases in accordance with the present temperature in the bore-holes. These facts suggest that the storage process of paleodose is strongly influenced not only by the time and intensity of exposure but also by the paleotemperature of the formation. An original paleo-dose in quartz might be set to zero by the magma intrusion of the Kurikomayama volcanic group, resuming the storage of electrons in trap levels afterwards.
TL intensities of quartz in the southern part of this area are smaller than those in the northern part. This suggests that the duration of hydrothermal activity in the south part has been relatively long.
In conclusion, the accumulation of paleodose is affected by the temperature due to geothermal activity. These features show that the TL method may be applicable to geothermal exploration.
