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

古地震地质年代学 - 通过地震对断层物质进行测年 -

• 批准号: 11440151
• 负责人: ITAYA Tetsumaru
• 金额: $ 6.14万
• 依托单位: Okayama University of Science
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B).
• 财政年份: 1999
• 资助国家: 日本
• 起止时间: 1999 至 2000
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-11440151/
• 关键词: earthquake; fault materials; fault gouge; mica-clay minerals; K-Ar method; Ar-Ar method; TL method; ESR method; 年代測定; 放射線損傷法; 断層; シュードタキライト

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.

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。

项目成果

Nishimura, Y., Coombs, D.S., Landis, C.A.and Itaya, T.: "Continuous metamorphic gradient documented by graphitization and K-Ar age, southeast Otago, New Zealand."American Mineralogist. 85. 1625-1636 (2000)

Nishimura, Y.、Coombs, D.S.、Landis, C.A. 和 Itaya, T.：“通过石墨化和 K-Ar 年龄记录的连续变质梯度，新西兰奥塔哥东南部。”美国矿物学家。

Tsujimori, T.and Itaya, T.: "Blueschist-facies metamorphism during Paleozoic orogeny in southwestern Japan : Phengite K-Ar ages of blueschist-facies tectonic blocks in a serpentinite melange beneath early Paleozoic Oeyama ophiolite."The Island Arc.. 8. 19

Tsujimori, T. 和 Itaya, T.：“日本西南部古生代造山运动期间的蓝片岩相变质作用：早古生代大江山蛇绿岩下蛇纹岩混杂岩中蓝片岩相构造块的白云母 K-Ar 年龄。”岛弧.. 8

Ohtani, T., Fujimoto, K., Ito, H., Tanaka, H., Higuchi, T.and Tomida, N.: "Fault Rocks and Paleo- to Recent Fluid Characteristics from the Borehole Survey of the Nojima Fault ruptured in the 1995 Kobe earthquake, southwest Japan."Journal of Geophysical Re

Ohtani, T.、Fujimoto, K.、Ito, H.、Tanaka, H.、Higuchi, T. 和 Tomida, N.：“来自野岛断层破裂钻孔测量的断层岩石和古至近期流体特征

Tanaka,H.,Fujimoto,K.,Ohtani,T.and Ito,H.: "Role of each shear zone in a fault zone during seismic cycles, clarified by structural and chemical characterization of fault rocks along the GSJ core penetrating."Journal of Geophysical Research. (印刷中).

Tanaka, H.、Fujimoto, K.、Ohtani, T. 和 Ito, H.：“地震周期期间断层带中每个剪切带的作用，通过沿 GSJ 核心穿透的断层岩石的结构和化学特征得以阐明。”地球物理研究杂志（正在出版）。

Itaya, T.and Fujino, M.: "K-Ar age - chemistry - fabric relations of phengite from the Sanbagawa high pressure schists, Japan."The Island Arc. 8. 523-536 (1999)

Itaya, T. 和 Fujino, M.：“来自日本三波川高压片岩的多硅白云岩的 K-Ar 年龄 - 化学 - 组构关系。”岛弧。