Cooling and denudation history of the Tsuruga body of Kojaku granite, southwest Japan, constrained from multi-system thermochronology

Sueoka, Shigeru   ; Umeda, Koji; Yasue, Kenichi; Niwa, Masakazu   ; Shimada, Koji   ; Ishimaru, Tsuneari ; Danhara, Toru*; Iwano, Hideki*; Yagi, Koshi*

We applied multi-system thermochronology to the Tsuruga body of the Kojaku granite to constrain the cooling/denudation history of the Tsuruga area. Based on the thermochronometric results and other data, we reconstructed the cooling and denudation histories of the Tsuruga body as below: (1) the Tsuruga body intruded at c.a. 68 Ma at the depth of 4-5 km, (2) rapidly cooled down to c.a. 200C by heat conduction within a few million years or less, and (3) slowly cooled due to peneplanation during the Cenozoic. This cooling/denudation history is consistent with the observations that cataclasite and fault gouge are dominant in the crush zones of the Tsuruga body, that similar slow cooling histories over the Cenozoic are estimated in the surrounding areas based on thermochronometric ages, and that the amount of denudation in the last few million years in the Tsuruga area is inferred at less than several hundred meters from the elevations of the uplifted peneplains.