Timing of intrusion of the Otagiri granite with respect to the deformation and metamorphism in Ryoke belt in the Ina district, central Japan: Examination by Rb-Sr whole rock isochron ages
Timing of intrusion of the Otagiri granite with respect to the deformation and metamorphism in Ryoke belt in the Ina district, central Japan: Examination by Rb-Sr whole rock isochron ages
复制标题
日本中部伊那地区 Ryoke 带变形和变质作用的 Otagiri 花岗岩侵入时间：用 Rb-Sr 全岩等时线年龄检验
DOI：
10.2465/ganko.89.269
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发表时间：
1994
期刊：
影响因子：
--
通讯作者：
M. Yuhara
中科院分区：
文献类型：
--
作者：
M. Yuhara
对出露于良带伊那地区的良带中较年轻的侵入岩之一--大切二云母花岗岩进行了岩石学和Rb-Sr年代学研究。在野外识别出北方、中部和南部三组花岗岩体，前两组侵入的是硅线岩带的岩屑质和砂屑质片麻岩，最后一组侵入的是前一组花岗岩--市田花岗岩。获得了北方、中部和南部花岗岩体的Rb-Sr全岩等时线年龄分别为71.1 ± 6.8Ma、99.0 ± 10.9Ma和92.7 ± 13.8Ma。由于不同岩体的初始Sr、Nd同位素比值也不同，这三组花岗岩可能来自不同时代的岩浆。这些花岗岩体与周围片麻岩的侵入关系表明，辽辽带的主要变质变形期超过100 Ma。同样，市田花岗岩和稻川花岗岩的年龄也在90 Ma以上。与这些岩体相当的花岗质岩石广泛分布于本州中部的Ryoke带，因此表明在包括Ryoke带在内的白垩纪花岗岩地体的西南部有90-100 Ma花岗岩的广泛侵入。
Petrology and Rb-Sr chronology were studied for Otagiri two-mica granite, one of the younger intrusives in the Ryoke belt, which are exposed in the Ina district of the Ryoke belt. Three groups, northern, central and southern granite bodies, were identified in the field, with the former two intruding litic and psammitic gneisses of sillimanite zone, and the last intruding a foregoing granite, the Ichida granite. Distinct Rb-Sr whole rock isochron ages, 71.1 ± 6.8 Ma, 99.0 ± 10.9 Ma, 92.7 ± 13.8 Ma were obtained for the northern, central and southern granite bodies, respectively. Because the initial Sr and Nd isotopic ratios are also different among different granite bodies, those three groups were probably derived from distinct magmas at different ages. The intrusive relations between these granite bodies and the surrounding gneiss indicate that the main stage of metamorphism and deformation of the Ryoke belt were older than 100 Ma. Likewise, Ichida granite and Inagawa granite were 90 Ma or older. Granitic rocks equivalent to those bodies are widely distributed in the Ryoke belt in central Honshu, thus suggest a widespread intrusion of the 90-100 Ma granites in the southwestern parts of the Cretaceous granite terrain including the Ryoke belt.