11:45 AM - 12:00 PM
[SCG63-11] Kinematics and K-Ar geochronology of the Median Tectonic Line of western Shikoku, south-west Japan.
Keywords:Median Tectonic Line, Paleogene, Kinematic history, K-Ar geochronology
The purpose of this study is to date the fault movements, it carried out that the K-Ar age measurements of fault gouge sampled at area avoided overlapping deformation of movement phase divided by the investigation of map, outcrop, and section scale. The measurement object intends for authigenic illite produced by the fault movement. The problem of this measurement method is that it is difficult to separate only authigenic illite from sample, because it consists of detrital illite in samples of fault distributed in wall rocks of sedimentary rock. Therefore, the measurements are the mixed age and become the measurements that are older than the age of the fault movement. We are going to estimate the true age of fault movement by analyzing the polytype. In addition, it intend to analyze the change of ages by the particle size and the polytype quantification based on dating of illite of 3 fraction (0.2-0.4, 0.4-1.0, 1.0-2.0μm) for 1 sample. It shows result of the K-Ar age measurements before the analysis of polytype (Table1). Based on the K-Ar age measurements, it is expected to understand the periods of Ichinokawa phase and Pre-Tobe phase in more detail.
Kubota, Y., Takeshita, T., 2008. Island Arc, vol. 17, p.129-151.; Kubota, Y., Takeshita, T., 2015. The 122nd annual meeting of the geological society of Japan abstract. p.125.; Shibata, K., Nakajima T., Sangawa A., Uchiumi S. & Aoyama H., 1989. K-Ar ages of fault gouges from the Median Tectonic Line in Shikoku. Bulletin of the Geological Survey of Japan . 40, p.661-671.