九州の新生代深成岩類・火山岩類・火砕岩類のフィッション・トラック年代の総括(1)

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Zircon fission-track ages from the Tertiary granitic rocks and the pyroclastic rocks in Kyushu, which were reported by the author in several papers for the past thirteen years, have been compiled in this paper. All the ages of seventeen samples from eleven granitic bodies in south Kyushu concentrate around 14 Ma. There are no granitic rocks with zircon fission-track ages of 21-23 Ma. This fact indicates that these eleven granitic bodies in south Kyushu cooled at virtually the same time. The fission-track ages of the Goto granitic rocks and the Fukue pyroclastic flow deposits are 15±2 Ma and 20±2 Ma, respectively. Although there was an opinion which the Fukue pyroclastic flow deposits overlay on the Goto granitic rocks, the fission-track ages indicate that the Goto granitic rocks are younger than the Fukue pyroclastic flow deposits. Thirteen fission-track ages of the pyroclastic rocks (pyroclastic flow deposits and tuff beds) from the Tertiary formations in north and northwest Kyushu have also been compiled in this paper. These ages serve as important time markers in compiling the Tertiary geologic history of north and northwest Kyushu.
九州大学の論文