Timing of the cataclastic deformation along the Akaishi Tectonic Line, central Japan

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doi: 10.1007/s004100050065
Authors:Tanaka, H.; Uehara, N.; Itaya, T.
Author Affiliations:Primary:
Ehime University, Matsuyama, Japan
Sumitomo Cement Company, Japan
Okayama University of Science, Japan
Volume Title:Contributions to Mineralogy and Petrology
Source:Contributions to Mineralogy and Petrology, 120(2), p.150-158. Publisher: Springer International, Heidelberg-New York, International. ISSN: 0010-7999
Publication Date:1995
Note:In English. 25 refs.; illus., incl. 1 table, geol. sketch map
Summary:This paper presents K-Ar ages of cataclasites and fault gouges from the Akaishi Tectonic Line (ATL), central Japan. Petrological and mineralogical features of these rocks are also examined. Based on the results, the hypothesis that the K-Ar ages of these rocks represent the age of hydrothermal alteration associated with the fault movement is tested. Intensity of deformation and alteration increase passing from host rock into cataclasite and finally into fault gouge. This increase corresponds with an increase in the value of crystallinity index (Kubler index) of the micaceous minerals contained in these rocks. Furthermore, the degree of rejuvenation of K-Ar ages of the micaceous minerals increases in the same sense. A correlation of K-Ar ages (plotted on the y axis) vs Kubler index (plotted on the x axis) yields a concave curve asymptotically parallel with the x axis at ∼ 15 m.y. This curve is interpreted to represent the mode of decrease of the relative amounts of inherited Ar in the K-Ar system of the micaceous minerals, corresponding with an increase in the intensity of deformation and alteration. Inclination of the curve becomes zero if all the inherited Ar is lost from the K-Ar system of the micaceous minerals. Thus, it is concluded that the hydrothermal alteration occurred at approximately 15 m.y. The strike-slip basin along the ATL formed in the middle Miocene. The K-Ar dating of ATL gouges indicates that the ATL was active simultaneously with formation of the strike-slipe basin along its trace during the Middle Miocene. [P.Br.]
Subjects:Absolute age; Ar-40; Argon; Cataclasis; Crystallinity; Dates; Deformation; Fault zones; Gouge; Hydrothermal conditions; Isotopes; K/Ar; Noble gases; Stable isotopes; Tectonics; Akaishi Mountains; Asia; Far East; Honshu; Japan; Japanese Alps; Akaishi tectonic line
Abstract Numbers:96M/50
Record ID:1996004476
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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