Geochronology of paleo-earthquake -dating of fault materials by earthquake-

在对地震形成的断层岩进行识别后，采用K-Ar、Ar-Ar和辐射损伤等方法对古地震断层运动过程中形成的物质进行测年。为了在TL和ESR测年中估计自然辐射水平，购买了便携式γ射线计。我们还构建了用于单矿物颗粒Ar-Ar定年的自动激光步进加热系统。许多构造地质学家支持我们对断层岩石进行采样，主要是来自爱姬县大岛的伪岩，来自日本Atotsugawa、Hatagawa、Tasuke和Tanakura系统的断层泥，以及尼泊尔的MCT和韩国的梁山断层。用脉冲激光氩/氩光斑测年法测定了大岛伪石质及其宿主变质岩的年代。后一种结果为角闪岩的100-110Ma，前一种结果为60-80Ma。尼泊尔MCT的断层年龄约为3Ma， Tanakura的断层年龄约为40-50Ma， Yangson的断层年龄约为38-46Ma。在Atotsu系统中，年龄随着花岗岩分离物粒度的减小而变小。这种趋势在沉积岩分离物中没有观察到。然而，年龄在60Ma左右。当K离子被NH4离子交换时，其年龄比原蒙脱石的年龄大2-5%。我们已经发表了20多篇关于该项目的成果和相关学科的论文。

This is to date the materials formed during fault movement accomapnied with paleo-earthquakes by K-Ar, Ar-Ar and radiation damage methods after the identification of fault rocks formed by earthquakes.In order to estimate natural radiation level in TL and ESR dating, a portable γ-ray meter was purchased. We also constructed the automated laser step heating system for Ar-Ar dating of single mineral grain.Many structural geologists supported us for sampling of fault rocks, mainly pseudotachlytes from Oshima of Ehime Prefecture and fault gouges from Atotsugawa, Hatagawa, Tasuke and Tanakura systems in Japan, and from MCT in Nepal and Yangsan fault in Korea.Oshima pseudotachlytes and their host metamorphic rocks were dated with the Ar/Ar spot daing method using a pulsed laser. The later results give 100-110Ma for amphiboles and the former, 60-80Ma. The ages of gouges are about 3Ma for the Nepal MCT, 40-50Ma for the Tanakura, 38-46Ma for the Yangson. In the Atotsu system, the ages become younger with decreasing grain size of separates from granites. This tendency is not observed in the separates from sedimentary rocks. However, the ages are about 60Ma.We examined the discordant age relations due to K ion trapped in the expanded layers of smectite When K ion is exchanged by NH4 ion, the ages get 2-5% older than those of the original smectite.We have published more than 20 papers on the results of this project and the related subjects.