Sm–Nd, Rb–Sr and K–Ar geochronology of the Higo metamorphic terrane, west‐central Kyushu, Japan
Sm–Nd, Rb–Sr and K–Ar geochronology of the Higo metamorphic terrane, west‐central Kyushu, Japan
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日本九州中西部肥后变质地体的 Sm-Nd、Rb-Sr 和 K-Ar 年代学
DOI：
10.1046/j.1440-1738.1999.00240.x
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发表时间：
1999
期刊：
影响因子：
1.5
通讯作者：
Y. Kagami
中科院分区：
文献类型：
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作者：
T. Hamamoto;Y. Osanai;Y. Kagami
位于日本西南部九州岛中西部的HIGO变质地体由绿片岩至麻粒岩相变质岩组成。变质地体南部主要为石榴石-黑云片麻岩和石榴石-堇青石-黑云片麻岩，含斜方辉石或堇青石的S型英云闪长岩中含有少量的角闪辉长岩。测定了这些岩石的Rb-Sr、Sm-ND和K-Ar同位素年龄。石榴石-黑云片麻岩的Sm-ND年龄为227.1±4.9 Ma，Rb-Sr年龄为101.0±1.0 Ma。角闪辉长岩的Sm-ND年龄为257.9±2.5 Ma，K-Ar年龄为103.4±1.1 Ma。同一样品的年龄差异是由于不同体系和矿物的闭合温度不同造成的。石榴石-堇青石-黑云母片麻岩含有粗粒石榴石，具有明显的带状结构，色差明显(核心：暗红色；边缘：粉红色)。石榴石核部和边缘的Sm-Nd等时线年龄分别为278.8±4.9Ma和226.1±28.4Ma(初始143Nd/144Nd值分别为0.512311±0.000005和0.512277±0.000038)。这些年龄接近石榴石核心和边缘的形成。此前曾有人认为，HIGO变质地体属于Ryoke变质带。但前者岩石的锶、钕同位素特征与Ryoke变质岩不同，而与Ryoke年轻花岗岩中的麻粒岩包体相似。
The Higo metamorphic terrane situated in west‐central Kyushu island, southwest Japan, is composed of greenschist‐ to granulite‐facies metamorphic rocks. The southern part of the metamorphic terrane consists mainly of garnet–biotite gneiss and garnet–cordierite–biotite gneiss, and orthopyroxene or cordierite‐bearing S‐type tonalite with subordinate amounts of hornblende gabbro. Rb–Sr, Sm–Nd and K–Ar isotopic ages for these rocks have been determined here. The garnet–biotite gneiss gives an Sm–Nd age of 227.1 ± 4.9 Ma and a Rb–Sr age of 101.0 ± 1.0 Ma. The hornblende gabbro has an Sm–Nd age of 257.9 ± 2.5 Ma and a K–Ar age of 103.4 ± 1.1 Ma. These age differences of the same samples are due to the difference in the closure temperature for each system and minerals. The garnet‐cordierite–biotite gneiss contains coarse‐grained garnet with a zonal structure conspicuously distinguished in color difference (core: dark red; rim: pink). Sm–Nd internal isochrons of the garnet core and the rim give ages of 278.8 ± 4.9 Ma (initial 143Nd/144Nd ratio = 0.512311 ± 0.000005) and 226.1 ± 28.4 Ma (0.512277 ± 0.000038), respectively. These ages are close to formation of the garnet core and the rim. It has been previously suggested that the Higo metamorphic terrane belongs to the Ryoke metamorphic belt. But Sr and Nd isotopic features of the rocks from the former are different from those of the Ryoke metamorphic rocks, and are similar to those of the granulite xenoliths contained in the Ryoke younger granite.
日本九州中西部肥后变质岩中的硅藻土和变质岩。
DOI：
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发表时间：
2005
期刊：
J.Mineralogical and Petrological Sciences 100, No.1
影响因子：
--
作者：
Kobayashi T;Obata;M.;Yoshimura;Y.
通讯作者：
Y.