Cooling and Denudation History of the Tsuruga Body of Kojaku Granite, Southwest Japan, Constrained from Multi-system Thermochronology
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- SUEOKA Shigeru
- Japan Atomic Energy Agency
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- UMEDA Koji
- Japan Atomic Energy Agency
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- YASUE Ken-ichi
- Japan Atomic Energy Agency
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- NIWA Masakazu
- Japan Atomic Energy Agency
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- SHIMADA Koji
- Japan Atomic Energy Agency
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- ISHIMARU Tsuneari
- Japan Atomic Energy Agency
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- DANHARA Tohru
- Kyoto Fission-Track Co., Ltd
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- IWANO Hideki
- Kyoto Fission-Track Co., Ltd
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- YAGI Koshi
- Hiruzen Institute for Geology and Chronology Co., Ltd
Bibliographic Information
- Other Title
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- 複数の熱年代学的手法に基づいた江若花崗岩敦賀岩体の冷却・削剥史
- フクスウ ノ ネツ ネンダイガクテキ シュホウ ニ モトズイタ コウワカハナオカガン ツルガガンタイ ノ レイキャク ・ サクハクシ
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Abstract
In this study, multi-system thermochronology, i.e., fission-track (FT), K-Ar and U-Pb methods are used to identify the cooling and denudation history of the Tsuruga body of Kojaku granite, southwest Japan. Apatite FT age of 51.8 ± 6.5 Ma, zircon FT age of 70.4 ± 2.0 Ma, biotite K-Ar ages of 66.7–62.0 Ma, and zircon U-Pb age of 68.5 ± 0.7 Ma were obtained for granitic samples, whereas plagioclase K-Ar ages of 19.1–18.8 Ma and whole-rock K-Ar age of 19.0 ± 2.9 Ma were inferred for the basaltic dyke intruding into the granite. The zircon FT lengths are not significantly shorter than their initial lengths, implying rapid cooling at the zircon FT partial annealing zone (PAZ). On the other hand, the apatite FT length distribution shows a typical pattern for granitic pluton without reheating, indicating a slow cooling history at the apatite FT PAZ. Based on the results of these thermochronometric analyses, inverse thermal calculations using the FT data, and simple thermal conduction modeling of the granitic body, the cooling and denudation histories of the Tsuruga body are reconstructed: (1) the Tsuruga body intruded at ca. 68 Ma, late Cretaceous, at a depth of several kilometers, (2) rapidly cooled to below the zircon FT PAZ by heat conduction within a few million years or less, and (3) slowly cooled due to peneplanation during the past 50–60 million years. On the other hand, the whole-rock Rb-Sr age previously reported for the Kojaku body is younger than when the cooling curve of the Tsuruga body obtained by this study intersects with the closure temperature of the whole-rock Rb-Sr system. This may imply a time lag between the formation ages of these bodies, but more thermochronometric studies are required to draw a definitive conclusion. The K-Ar ages of the basaltic dyke are interpreted as its formation age, indicating that dyke intrusion was associated with the Green Tuff movement.
Journal
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- Journal of Geography (Chigaku Zasshi)
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Journal of Geography (Chigaku Zasshi) 125 (2), 201-219, 2016
Tokyo Geographical Society
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Details 詳細情報について
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- CRID
- 1390001204237799808
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- NII Article ID
- 130005150919
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- NII Book ID
- AN00322536
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- ISSN
- 18840884
- 0022135X
- http://id.crossref.org/issn/00221341
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- NDL BIB ID
- 027313044
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- Text Lang
- ja
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- Data Source
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- JaLC
- NDL
- Crossref
- CiNii Articles
- KAKEN
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- Abstract License Flag
- Disallowed