Extensional stress accompanied by Miocene near-trench magmatism in the southern Kii Peninsula, SW Japan
Extensional stress accompanied by Miocene near-trench magmatism in the southern Kii Peninsula, SW Japan
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DOI：
10.1016/j.jseaes.2022.105266
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发表时间：
2022-06-02
影响因子：
3
通讯作者：
Hirata, Takafumi
中科院分区：
文献类型：
--
作者：
Haji, Toshiki;Yamaji, Atsushi;Hirata, Takafumi
大量的近海沟岩浆活动开始在熊野地区，日本西南部，约在。十五年前岩浆活动形成了岩基、坩埚和无数的岩脉。已知这些岩脉垂直于南海海槽，并由年轻的地层所容纳，这些地层以平行于海槽的轴线褶皱。因此，有人认为，在日本海弧后开启后不久，岩浆活动伴随着海沟垂直挤压。在这项研究中，我们获得了中新世早至中期熊野群和盐之崎火成杂岩中的14条长英质脉和151条基性岩脉的方位数据。两个数据集的反演产生了一个正常的断层应力状态与NE-SW扩展。该取向与沟槽的取向以高角度相交。我们还从两个长英质脉岩中获得了14.5 +/- 1.5和13.9 +/-1.4Ma的锆石裂变径迹年龄。这些年龄和现有的放射性测量和微体古生物学数据表明，这两组岩墙形成于约。14.5 MA.大、中尺度构造表明火成岩中的沟槽垂直缩短，表明褶皱发生在岩浆作用之后。我们解释了张应力是由于熊野地区下的岩基的侵位引起的隆起。推断的正断层应力制度提出了怀疑流行的构造模型，日本西南部，依赖于从伸展到压缩的过渡约。十五年前
Voluminous near-trench magmatism began in the Kumano area, SW Japan, at ca. 15 Ma. The magmatism formed batholiths, cauldrons, and numerous dikes. It has been known that The dikes are oriented perpendicular to the Nankai Trough, and are hosted by young formations that are folded with axes parallel to the trench. Therefore, it has been considered that the magmatism was accompanied by trench-perpendicular compression during the period shortly after backarc opening in the Japan Sea. For this study, we obtained orientation data from 14 felsic and 151 mafic dikes in the early to middle Miocene Kumano Group and Shionomisaki Igneous Complex. Inversion of both datasets yields a normal-faulting stress regime with NE-SW extension. This orientation meets at a high angle with that of the trench. We also obtained zircon fission-track ages of 14.5 +/- 1.5 and 13.9 +/- 1.4 Ma from two felsic dikes. These ages and existing radiometric and micropaleontological data show that both the groups of dikes were formed at ca. 14.5 Ma. Large- and meso-scale structures indicating trench-perpendicular shortening in igneous rocks suggest that the folding took place after the magmatism. We interpret that the extensional stress resulted from uplift caused by the emplacement of a batholith under the Kumano area. The inferred normal-faulting stress regime raises doubts about popular tectonic models of SW Japan that rely on a transition from extension to compression at ca. 15 Ma.