The new U-Pb age data of igneous rocks in Nakadorijima Island, Goto Islands, Nagasaki Prefecture, was reported by research groups of Nagasaki University, National Museum of Nature and Science, and Saga University

The research groups of Dr. Yoshimitsu Suda of Nagasaki University, Dr. Kenichiro Tani of the National Science Museum, and Prof. Susumu Kakuen of Saga University have presented a detailed geological map (1/10000) of the Tannayama area of Nakadorijima Island in the Goto Islands, Nagasaki Prefecture, and results of the U-Pb dating of igneous rocks in the Tannayama area. The U-Pb dating using zircon from the igneous rocks of the Goto Islands was the first attempt and carried out using a Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) at the National Museum of Nature and Science (Tsukuba). From the igneous rocks of the Tannayama area, the ages of 14.7 Ma ± 0.3 Ma (gabbro), 15.9 Ma ± 0.5 Ma (granite), 15.4 Ma ± 0.9 Ma (granite) and 15.1 Ma ± 2.1 Ma (rhyolite) were obtained. In addition, the age of 14.5 Ma ± 0.7 Ma was from the granite in Yagatamesaki (1 Ma represents 1 million years ago).

The Japanese archipelago was formed by the break-up of the eastern margin of the Eurasian continent from ca. 25 to 15 million years ago. At 15 million years ago, when the igneous rocks in Goto Islands were generated, the Japan Sea and the Japanese archipelago was formed by the end of break-up activity, and the young and hot Philippine Sea plate began to subduct under the southwestern Japan. The age data indicate that the igneous rocks in the Nakadorijima Island, were formed at the earliest stage of igneous activity in the Japanese archipelago, which are important research target for clarifying the tectonics for the formation of Japanese archipelago during the middle Miocene.

Geological map of Tannayama area and results of U-Pb dating

URL : https://doi.org/10.1111/iar.12390

Title:
Petrogenetic implications and geochronology of middle Miocene Tannayama igneous rocks, Goto Islands, Japan Sea southern margin, northwestern Kyushu, Japan

Authors:
Yoshimitsu Suda（Nagasaki University）

Kenichiro Tani（National Museum of Nature and Science）

Miho Yamaguchi（Nagasaki University）

Susumu Kakubuchi（Saga University）

Article:
Island Arc, Volume 30, Issue 1, January/December 2021, e12390, 24p.

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