Reconstructing the thermal structure of shallow crust using OSL-thermometry of K-feldspar from deep borehole core; Case studies in the Japanese Islands

Ogata, Manabu ; King, G. E.*; Herman, F.*; Yamada, Ryuji*; Omura, Kentaro*; Sueoka, Shigeru   

Optically stimulated luminescence (OSL)-thermometry can be used to reconstruct the thermal structure in slowly denuded regions where infrared stimulated luminescence (IRSL) signals of samples obtained from deep boreholes are measured and evaluated with depth. Only one study had explored this approach, using a target mineral of Na-feldspar. We applied multi-OSL-thermometry to K-feldspar obtained from deep borehole core samples drilled at the Tono (MIZ-1) and Rokko regions (Kabutoyama), which are well-documented thermally stable crustal environment. For the K-feldspar obtained from the MIZ-1 core, the inverted temperatures for the IRSL50 C of the samples at a depth of 1 km (40 C) were consistent with the in-situ temperatures. The results suggest that the application of OSL-thermometry to K-feldspar in a borehole is useful to reconstruct the palaeothermal condition. In this presentation, we will also show the results of the Kabutoyama core to draw more comprehensive conclusions.