Rb-Sr geochronology of the Hikami granite, Kitakami mountains, Japan.
Rb-Sr geochronology of the Hikami granite, Kitakami mountains, Japan.
复制标题
日本北上山 Hikami 花岗岩的 Rb-Sr 地质年代学。
DOI：
10.2343/geochemj.8.193
复制
发表时间：
1974
影响因子：
0.8
通讯作者：
K. Shibata
中科院分区：
文献类型：
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作者：
K. Shibata
日本东北北上南山Hikami花岗岩的全岩Rb-Sr年龄为339±12m.y，初始87Sr/86Sr比值为0.7079±0.0003，表明该花岗岩的侵入时间为晚泥盆世至早石炭世。Hikami花岗岩的初始87Sr/86Sr比值略高，表明花岗岩吸收了一定数量的老地壳。其等时年龄为334m.y，初始87Sr/86Sr比值为0.7129。结果表明，在花岗岩侵入时期，片麻岩整体发生了Sr同位素均一化。较高的87Sr/86Sr比值表明片麻岩起源于前寒武纪。泥盆纪Ono组的花岗岩巨石没有定义任何等时线，而志留纪Kawauchi组的砂岩则给出了264万年的明显年龄。砾石和砂岩的全岩体系在Rb和Sr方面可能保持开放，这可能是由于它们参与了沉积过程。白垩纪托诺和Kesengawa花岗岩的Rb-Sr同位素数据证实了日本东北部几乎所有火成岩，无论年龄大小，其初始87Sr/86Sr比值都很低，反映了日本东北部地壳的独特性质。
Whole-rock samples of the Hikami granite from the southern Kitakami mountains in Northeast Japan give a Rb-Sr age of 339 ± 12m.y with an initial 87Sr/86Sr ratio of 0.7079 ± 0.0003, indicating that the granite intruded in the late Devonian to early Carboniferous time. A slightly high initial 87Sr/86Sr ratio for the Hikami granite suggests that the granite assimilated some amount of older crust. The Tsubonosawa gneiss, which is contained in the Hikami granite as xenolithic masses, gives an isochron age of 334m.y with an initial 87Sr/86Sr ratio of 0.7129. The results show that the Sr isotopic homogenization occurred among the whole masses of the gneiss at the time of granite intrusion. A higher initial 87Sr/86Sr ratio suggests that the gneiss originated in the Precambrian time. Granite boulders from the Devonian Ono formation do not define any isochron, whereas the sandstone from the Silurian Kawauchi formation gives an apparent age of 264m.y. The whole-rock systems of boulders and sandstone may have remained open with respect to Rb and Sr, probably because of their involvement in sedimentary process. The Rb-Sr isotopic data for the Cretaceous Tono and Kesengawa granites confirm the evidence that almost all igneous rocks in Northeast Japan, irrespective of age, have low initial 87Sr/86Sr ratios, reflecting a distinctive nature of crust in Northeast Japan.
,黑濑川构造带的形成过程
DOI：
--
发表时间：
2012
期刊：
影响因子：
--
作者：
小山内康人・中野伸彦・足立達朗・米村和紘・吉本紋・Setiawan;N.・石塚英男・川嵜智佑・外田智千
通讯作者：
N.・石塚英男・川嵜智佑・外田智千