SHRIMP zircon and EPMA monazite dating of granitic rocks from the Maizuru terrane, southwest Japan: Correlation with East Asian Paleozoic terranes and geological implications
SHRIMP zircon and EPMA monazite dating of granitic rocks from the Maizuru terrane, southwest Japan: Correlation with East Asian Paleozoic terranes and geological implications
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DOI：
10.1111/j.1440-1738.2008.00623.x
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发表时间：
2008-09
期刊：
影响因子：
1.5
通讯作者：
M. Fujii;Y. Hayasaka;K. Terada
中科院分区：
文献类型：
--
作者：
M. Fujii;Y. Hayasaka;K. Terada
舞鹤岩分布于日本西南部的内带，分为北方、中部和南部三个亚带，各亚带的岩性组合不同。与由八久野蛇绿岩组成的南部带形成鲜明对比，北方带被高角度断层细分为西部和东部体，主要通过变形花岗岩和泥质片麻岩的存在来识别。这种组合表明与成熟的大陆块体有密切关系;这一点得到了产状、岩石学和同位素数据的支持。新获得的高质量分辨率离子探针（SHRIMP）锆石U-Pb年龄显示，西岩体花岗岩的侵入年龄为424 ± 16和405 ± 18 Ma（志留纪-泥盆纪），东岩体花岗闪长岩的侵入年龄为249 ± 10和243 ± 19 Ma（二叠纪-三叠纪）。岩体西部的花岗岩也显示出约580和765 Ma的继承性锆石年龄。此外，电子探针（EPMA）独居石U-Th-总Pb测年给出的年龄约为475-460 Ma。北方带志留纪-泥盆纪花岗岩的侵入时代、继承时代、产出方式和地质背景均与俄罗斯普里莫耶南部的Khanka地块和日本东北部南北上江的Hikami花岗岩相似。我们认为，北方带的志留纪-泥盆纪和二叠纪-三叠纪花岗质岩石可能是通过三叠纪-晚侏罗世右行走滑运动并置的，并分别起源于Khanka地块和希达山。这项研究有力地支持了走滑运动的重要性，作为一种机制，导致在日本群岛，以及在东亚的古生代-中生代火山岩的结构重排。
Abstract The Maizuru terrane, distributed in the Inner Zone of southwest Japan, is divided into three subzones (Northern, Central and Southern), each with distinct lithological associations. In clear contrast with the Southern zone consisting of the Yakuno ophiolite, the Northern zone is subdivided into the western and eastern bodies by a high‐angle fault, recognized mainly by the presence of deformed granitic rocks and pelitic gneiss. This association suggests an affinity with a mature continental block; this is supported by the mode of occurrence, and petrological and isotopic data. Newly obtained sensitive high mass‐resolution ion microprobe (SHRIMP) zircon U–Pb ages reveal the intrusion ages of 424 ± 16 and 405 ± 18 Ma (Siluro–Devonian) for the granites from the western body, and 249 ± 10 and 243 ± 19 Ma (Permo–Triassic) for the granodiorites from the eastern body. The granites in the western body also show inherited zircon ages of around 580 and 765 Ma. In addition, electron probe microanalysis (EPMA) monazite U–Th–total Pb dating gives around 475–460 Ma. The age of intrusion, inherited ages, mode of occurrence, and geological setting of the Siluro–Devonian granites of the Northern zone all show similarities with those of the Khanka Massif, southern Primoye, Russia, and the Hikami granitic rocks of the South Kitakami terrane, Northeast Japan. We propose that both the Siluro–Devonian and Permo–Triassic granitic rocks of the Northern zone are likely to have been juxtaposed through the Triassic–Late Jurassic dextral strike‐slip movement, and to have originated from the Khanka Massif and the Hida terrane, respectively. This study strongly supports the importance of the strike‐slip movement as a mechanism causing the structural rearrangement of the Paleozoic–Mesozoic terranes in the Japanese Islands, as well as in East Asia.