Thermoluminescence as a new research tool for the evaluation of geothermal activity of the Kakkonda geothermal system, northeast Japan

Abstract

The thermoluminescence glow-curve of quartz in volcanic and pyroclastic rocks of the Miocene and Quaternary in the Kakkonda geothermal field was divided into L (low), M (medium) and H (high) peaks in order of increasing temperature. Thermoluminescence emission is independent of stratigraphic boundaries but it is closely related to surface geothermal manifestations. Thermally stimulated processes of thermoluminescence caused by natural annealing occurred in the Quaternary after the eruption of the Tamagawa Welded Tuffs; radiation storage processes then began, as a consequence of the temperature drop. Thermoluminescence behavior indicates natural temperature manifestations, together with the paleo-temperature history. The H peak was thermally stable compared to the L and M peaks, and the area within which the relative intensity of the H peak is less than 5% coincides with the surface zone where dominant fluid flow is convective. In addition, L and M peaks indicate that a relatively low-temperature fluid mixes with the hot upflow around the western margin of the ascending flow zone. Thermoluminescence characteristics reflect paleo-temperature history and are related to geothermal fluid flow. Thermoluminescence is an effective exploration technique for evaluating natural temperature manifestations and subterranean heat flow in geothermal systems.