Phengite K-Ar ages of the Yamagami Metamorphic Rocks in the Motai-Matsugataira Belt
Phengite K-Ar ages of the Yamagami Metamorphic Rocks in the Motai-Matsugataira Belt
复制标题
Motai-松平带山上变质岩白硅白云石K-Ar年龄
DOI：
10.5575/geosoc.2019.0042
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
T. Itaya
中科院分区：
文献类型：
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作者：
A. Miyashita;K. Yagi;T. Itaya
日本东北部岛弧东缘的莫泰-松平带（MMB）由古生代变质杂岩组成。该带内高P山神变质岩又分为高品位山神Ⅰ和低品位山神Ⅱ单元。 Yamagami I 变质岩主要由泥质片岩、绿帘角闪岩和石榴石角闪岩组成。金红石中钠长石的出现和角闪石的化学性质表明，Yamagami I 变质岩经历了 MMB 中最高级别的变质作用。泥质片岩和角闪岩的多硅白云母 K-Ar 年龄表明折返作用发生在 322 Ma 到 287 Ma 之间。这些山上变质岩的岩石学和地质年代学结果表明，MMB 的一部分可能是日本西南部 Renge 带的延伸。
The Motai–Matsugataira Belt (MMB) in the eastern margin of the northeastern Japan arc comprises Paleozoic metamorphic complexes. The high-P Yamagami metamorphic rocks in the belt are subdivided into the high-grade Yamagami I and low-grade Yamagami II units. The Yamagami I metamorphic rocks consist mainly of pelitic schist, epidote amphibolite, and garnet amphibolite. The occurrence of paragonite in rutile and the chemistry of amphiboles indicate that the Yamagami I metamorphic rocks underwent the highest-grade metamorphism in the MMB. Phengite K–Ar ages of the pelitic schists and amphibolitesindicateexhumation during 322 to 287 Ma. These petrological and geochronological results for the Yamagami metamorphic rocks indicate that part of the MMB is probably an extension of the Renge Belt of southwestern Japan.