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首页> 外文期刊>地質学雑誌 >Zircon U-Pb age and its geological significance of late Carboniferous and Early Cretaceous adakitic granites from eastern margin of the Abukuma Mountains,Japan
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Zircon U-Pb age and its geological significance of late Carboniferous and Early Cretaceous adakitic granites from eastern margin of the Abukuma Mountains,Japan

机译：日本Abukuma山脉东缘晚石炭世和早白垩世埃达克花岗岩的锆石U-Pb年龄及其地质意义

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摘要

The 'Wariyama Sheared Granodiorite' occurs along the east side of the Futaba Fault with the Wariyama uplift zone, Miyagi, Japan. Rocks from the 'Wariyama Sheared Granodiorite' can be geochemi-cally classified as typical adakite, and further subdivided into medium-grained and K_2O- and Sr-poorer rocks, and coarse-grained and K_2O- and Sr-richer rocks. Zircons from the former yield U-Pb ages of 308 ± 3 and 302 ± 4 Ma, whereas zircons from the latter have ages of 118 ± 2 and 117 ± 1 Ma. On the basis of these results, the 'Wariyama Sheared Granodiorite' can be redefined. The late Carboniferous granite is renamed the Wariyama Granite as in the past,but we use the term 'granite' in a broad sense as describing the rock type. The Early Cretaceous granite is newly defined as the Takase Granite. The Takase Granite crops out on the eastern side of the central region of the Wariyama Granite with faulted contact. The Takase Granite is divided into the SiO_2-poor Takase Granite A and the Si02-rich Takase Granite B. The U-Pb zircon age of 300 Ma obtained here corresponds to an interval of five major granitic events, and the timing of the onset of Permian granitic magmatism (280 Ma) may actually be ca. 300 Ma. Typical adakites are considered to be the product of slab melting, which occurred in response to unusual tectonic conditions, such as subduction of young lithosphere and/or an active ridge at ca. 300 Ma.
机译：“ Wariyama Sheared Granodiorite”发生在日本宫城县Wariyama隆升带的Futaba断层的东侧。来自“ Waryama Sheared Granodiorite”的岩石在化学上可以归类为典型的Adakite，并进一步细分为中粒和K_2O和Sr较差的岩石，以及粗粒和K_2O和Sr较丰富的岩石。前者的锆石的U-Pb年龄为308±3和302±4 Ma，而后者的锆石的年龄为118±2和117±1 Ma。根据这些结果，可以重新定义“ Wariyama剪切的花岗闪长岩”。已故的石炭纪花岗岩与过去一样被重命名为Wariyama花岗岩，但是我们在广义上使用“花岗岩”一词来描述岩石类型。白垩纪早期花岗岩被新定义为高濑花岗岩。高濑花岗岩出产于Wariyama花岗岩中心区域的东部，接触不良。 Takase花岗岩分为贫SiO_2的Takase花岗岩A和富含SiO2的Takase花岗岩B。这里获得的300 Ma的U-Pb锆石年龄对应于五个主要花岗岩事件的间隔，以及开始的时间。二叠纪花岗岩浆岩（280 Ma）实际上可能是大约。 300毫安典型的akakite被认为是板状融化的产物，它是对异常构造条件的响应，例如年轻的岩石圈俯冲作用和/或活动的山脊俯冲。 300毫安

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