U-Pb ages of Miocene near-trench granitic rocks of the Southwest Japan arc: implications for magmatism related to hot subduction
U-Pb ages of Miocene near-trench granitic rocks of the Southwest Japan arc: implications for magmatism related to hot subduction
复制标题
日本西南部岛弧中新世近海沟花岗岩的 U-Pb 年龄：对与热俯冲相关的岩浆作用的影响
DOI：
10.1017/s0016756819000785
复制
发表时间：
2019
影响因子：
2.3
通讯作者：
Anma Ryo
中科院分区：
文献类型：
--
作者：
Shinjoe Hironao;Orihashi Yuji;Anma Ryo
本文提出了一个新的锆石U-Pb年龄数据集，记录了中新世中期日本西南弧的火成岩活动，并讨论了其与日本海开放、菲律宾海板块迁移和国盆地年轻热岩石圈俯冲的关系。以岩脉和岩质侵入为特征的岩浆活动开始于约15.6 Ma的九州和喜岛。大部分岩浆活动发生在15.5 ~ 13.5 Ma之间，区域长600公里，宽150公里。海沟附近火成岩活动的U-Pb年龄未见沿弧趋势。我们的资料表明，所有中中新世近海沟火成岩活动都发生在日本海开口停止后，即16 Ma之后，这表明近海沟地区的熔体提取和花岗岩侵位对弧后开口有一定的影响。我们的数据还表明，日本弧与伊津-波宁-马里亚纳弧之间的海沟-海沟-海沟型三联结在15.6 Ma时到达了纪宜半岛的东侧。同生岩浆活动沿弧的广泛分布，除了与日本海张开有关的热楔地幔条件外，还需要海沟平行的热源，如海沟平行脊的俯冲或年轻且高度分段的脊-断裂带系统。
We present a new dataset of zircon U–Pb ages that document igneous activity in the SW Japan arc during middle Miocene time and discuss its relationship with the opening of the Japan Sea, Philippine Sea plate migration, and subduction of the young hot lithosphere of the Shikoku Basin. Precursory magmatism, characterized by dike and stock intrusions, started c. 15.6 Ma in both Kyushu and the Kii Peninsula. Most plutonism occurred between 15.5 and 13.5 Ma in an area 600 km long and 150 km wide. No along-arc trend was recognized in the U–Pb ages of igneous activity near the trench. Our data indicate that all near-trench middle Miocene igneous activity occurred immediately after the opening of the Japan Sea ceased, ie after 16 Ma, implying that melt extraction and the emplacement of granites in the near-trench region had some influence on the back-arc opening. Our data also imply that the trench–trench–trench-type triple junction between the Japan arc and the Izu–Bonin–Mariana arc must have reached the east side of the Kii Peninsula by 15.6 Ma. The wide distribution of contemporaneous magmatic activity along the arc requires a trench-parallel heat source, such as the subduction of a trench-parallel ridge or a young and highly segmented ridge–fracture zone system in addition to the hot wedge mantle condition related to the opening of Japan Sea.