Early Permian peak metamorphism recorded in U–Pb system of black slates from the Ogcheon metamorphic belt, South Korea, and its tectonic implication
Early Permian peak metamorphism recorded in U–Pb system of black slates from the Ogcheon metamorphic belt, South Korea, and its tectonic implication
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DOI：
10.1016/s0009-2541(02)00227-9
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发表时间：
2003-01
期刊：
影响因子：
3.9
通讯作者：
C. Cheong;G. Jeong;H. Kim;Man-Sik Choi;S. Lee;M. Cho
中科院分区：
文献类型：
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作者：
C. Cheong;G. Jeong;H. Kim;Man-Sik Choi;S. Lee;M. Cho
我们报告了韩国 Ogcheon 变质带碳质黑色板岩的 Pb-Pb 全岩和铀矿化学 Th-U-总 Pb 等时线法 (CHIME) 年龄。整个岩石样品的 Pb 同位素数据显示，该带东北部的两个露头的 207Pb/206Pb 年龄分别为 283±33 Ma 和 291±13 Ma。该带东北部和中部的铀矿 CHIME 年龄估计分别为 283±26 和 281±27 Ma。上述年龄在误差范围内均相同，代表了晚前寒武纪板内裂谷后变质作用高峰的时间。另一方面，该带西南部的207Pb/206Pb全岩年龄估计为194±27Ma，可能代表与侏罗纪花岗岩体侵入相关的接触热变质作用的时间。黑色板岩的 Rb-Sr 同位素数据没有定义任何有意义的等时线。本研究的早二叠世变质时代不支持任何有利于志留纪-泥盆纪或三叠纪时期主要构造变质作用的构造方案。相反，它证实了Ogcheon带中的两个区域，Ogcheon变质带和Taebaegsan带，在前者的主要构造框架形成之前彼此分离的可能性。我们的数据并不支持Ogcheon带对应于中国中东部三叠纪碰撞带的延续的观点。
We report Pb–Pb whole rock and uraninite CHemical Th–U–total Pb Isochron MEthod (CHIME) ages of carbonaceous black slates from the Ogcheon metamorphic belt, South Korea. The Pb isotopic data of whole rock samples yield207Pb/206Pb ages of 283±33 and 291±13 Ma for two outcrops from the northeastern part of the belt. The uraninite CHIME age is estimated at 283±26 and 281±27 Ma for the northeastern and the middle part of the belt, respectively. All of the above ages are identical within error ranges, and represent the timing of peak metamorphism after the late Precambrian intraplate rifting. On the other hand, the207Pb/206Pb whole rock age for the southwestern part of the belt is estimated at 194±27 Ma, probably representing the timing of contact thermal metamorphism associated with the intrusion of Jurassic granitic plutons. Rb–Sr isotopic data of the black slates do not define any meaningful isochron. The early Permian metamorphic age of this study does not support any tectonic scheme in favor of major tectonometamorphism at either the Silurian–Devonian or the Triassic time. Instead, it corroborates the probability that the two zones in the Ogcheon belt, the Ogcheon metamorphic belt and the Taebaegsan zone, were separated from each other before the development of major structural framework in the former. Our data do not support an idea that the Ogcheon belt corresponds to the continuation of the Triassic collision belt in east central China.