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

The thermoluminescence glow-curve of quartz in volcanic and pyroclastic rocks of the Miocene and Quaternary in the Kakkonda geothermal ®eld 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 Tu€s; 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 ¯uid ¯ow is convective. In addition, L and M peaks indicate that a relatively low-temperature ¯uid mixes with the hot up¯ow around the western margin of the ascending ¯ow zone. Thermoluminescence characteristics re¯ect paleo-temperature history and are related to geothermal ¯uid ¯ow. Thermoluminescence is an e€ective exploration technique for 0375-6505/00/$20.00 # 2000 CNR. Published by Elsevier Science Ltd. All rights reserved. PII: S0 37 5 -6 50 5 (9 9) 00 0 49 -8 Geothermics 29 (2000) 27±50 * Corresponding author. E-mail address: tsuchiya@bas.earth.tohoku.ac.jp (N. Tsuchiya). evaluating natural temperature manifestations and subterranean heat ¯ow in geothermal systems. # 2000 CNR. Published by Elsevier Science Ltd. All rights reserved.