The subduction of “hot” Shikoku Basin and the mantle upwelling related to the Japan Sea opening have induced extensive magmatism during the middle Miocene on both the back‐arc and island‐arc sides of southwest Japan. The Goto Islands are located on the back‐arc side of northwestern Kyushu, and middle Miocene granitic rocks and associated volcanic, hypabyssal, and gabbroic rocks are exposed. The igneous rocks at Tannayama on Nakadori‐jima in the Goto Islands consist of gabbronorite, granite, granite porphyry, diorite porphyry, andesite, and rhyolite. We performed detailed geological mapping at a 1:10 000 scale, as well as petrographical and geochemical analyses. We also determined the zircon U–Pb age dating of the igneous rocks from Tannayama together with a granitic rock in Yagatamesaki. The zircon U–Pb ages of the Tannayama igneous rocks show the crystallization ages of 14.7 Ma ± 0.3 Ma (gabbronorite), 15.9 Ma ± 0.5 Ma (granite), 15.4 Ma ± 0.9 Ma (granite porphyry), and 15.1 Ma ± 2.1 Ma (rhyolite). Zircons from the Yagatamesaki granitic rock yield 14.5 Ma ± 0.7 Ma. Considering field relationships, new zircon data indicate that the Tannayama granite formed at ~16–15 Ma, and the gabbronorite, granite porphyry, diorite porphyry, andesite, and subsequently rhyolite formed at 15–14 Ma, which overlaps a plutonic activity of the Yagatamesaki. The geochemical characteristics of the Tannayama igneous rocks are similar to those of the tholeiitic basalts and dacites of Hirado, and the granitic rocks of Tsushima in northwestern Kyushu. This suggests that the Tannayama igneous rocks can be correlated petrogenetically with the igneous rocks in those areas, with all of them generated by the upwelling of hot mantle diapirs during crustal thinning in an extensional environment during the middle Miocene.

中文翻译：

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日本五岛群岛中新世田中山火成岩的岩石成因意义和年代学

“热”四国盆地的俯冲和与日本海开放有关的地幔隆升，在日本西南部后弧和岛弧两侧的中新世中期都引起了广泛的岩浆作用。五岛群岛位于九州西北部的弧后侧，中新世中的花岗岩岩以及相关的火山岩，海底岩和辉长岩都暴露在外。五岛群岛中鸟岛的天南山火成岩由辉长岩，花岗岩，花岗岩斑岩，闪长斑岩，安山岩和流纹岩组成。我们以1:10 000的比例进行了详细的地质制图，并进行了岩石学和地球化学分析。我们还确定了田谷山火成岩与花岗岩在八g前崎的锆石U–Pb年龄年代。塔纳山火成岩的锆石U–Pb年龄显示出结晶年龄为14.7 Ma±0.3 Ma（辉长石），15.9 Ma±0.5 Ma（花岗岩），15.4 Ma±0.9 Ma（花岗岩斑岩）和15.1 Ma±2.1 Ma （流纹岩）。八g崎烧质花岗岩中的锆石产量为14.5 Ma±0.7 Ma。考虑到田间关系，新的锆石数据表明在约16-15 Ma形成了塔纳山花岗岩，辉长岩，花岗岩斑岩，闪长斑岩和安山岩以及随后的流纹岩在15-14 Ma形成，重叠了矢形岩的岩浆活动。 。谷山山火成岩的地球化学特征与平户的玄武岩和辉石以及九州西北部的对马岛的花岗岩具有相似的地球化学特征。