Early Permian zircon uranium-lead ages for plagiogranites in the Yakuno ophiolite, Asago district, Southwest Japan |
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Authors: | Charles T Herzig David L Kimbrough Yasutaka Hayasaka |
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Institution: | Department of Geological Sciences, Sun Diego State University, Sun Diego, CA 92182-1020 USA;1nstitute of Geology and Mineralogy, Hiroshima University, Hiroshima 72.4 Japan |
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Abstract: | Abstract Prior work has defined a two-stage history for Yakuno ophiolite petrogenesis consisting of older oceanic basement, and younger island-arc rocks and subordinate elastic rocks. First-stage Yakuno rocks have transitional-type M orb or oceanic plateau affinities, and second-stage Yakuno rocks are more similar to immature island-arc settings. Zircon U-Pb isotopic dates of plagiogranite from the Asago district of Southwest Japan yield crystallization ages of 285 ± 2 Ma for the first-stage ophiolite component, and 282 ± 2 Ma for the second-stage component of the ophiolite. These results indicate that the two petrologi-cally distinct components of the Yakuno ophiolite in this area formed in a short time interval in the Early Permian. The zircon U-Pb crystallization ages provide a maximum age for the base of the stratigraphically overlying Maizuru Group. |
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Keywords: | Japan ophiolite plagiogranites U-Pb Yakuno zircon |
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