The Taihua group on the southern margin of the North China craton: further insights from U–Pb ages and Hf isotope compositions of zircons
The Taihua group on the southern margin of the North China craton: further insights from U–Pb ages and Hf isotope compositions of zircons
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DOI：
10.1007/s00710-009-0062-5
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发表时间：
2009-06
影响因子：
1.8
通讯作者：
Xi‐sheng Xu;W. Griffin;Xi Ma;S. O’Reilly;Zhenyu He;Chengli Zhang
中科院分区：
文献类型：
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作者：
Xi‐sheng Xu;W. Griffin;Xi Ma;S. O’Reilly;Zhenyu He;Chengli Zhang
“太华群”是对分布于华北陆缘沿着的一系列古火山岩的统称。关于太华群的形成时代和热叠加作用一直存在争议，其与秦岭造山带的关系也一直不清楚。本文利用锆石U-Pb定年和Hf同位素分析的新资料，（来自熊耳山片麻岩）和一片黑云母片麻岩（蓝田-小秦岭剖面）表明上太华群形成于古元古代（2.3- 2.5Ga），原属华北陆块南缘的一部分在中生代秦岭造山运动中分离，并从原来的位置向北移动了约100公里。这表明太华群成为与秦岭造山带有关的构造带的一部分，现在又成为秦岭逆冲基底段的一部分。在秦岭造山运动之前，太华群在2.1Ga发生变质作用。锆石的初始Hf同位素组成以及全岩的正εNd（t）值表明，原始岩浆来源于年轻岩浆源，并与太古代地壳成分有一定的同化作用。
The "Taihua Group" is a collective term for a series of old terranes scattered along the southern margin of the North China Craton. The timing of formation and thermal overprinting of the Taihua Group have long been contentious, and its relationship with the Qinling orogenic belt has been unclear. In this study, new data from integrated in-situ U–Pb dating and Hf isotope analysis of zircons from an amphibolite (from the Xiong’ershan terrane) and a biotite gneiss (from the Lantian-Xiaoqinling terrane) indicate that the Upper Taihua Group formed during the Paleoproterozoic (2.3–2.5 Ga) and thus was originally part of the southern edge of North China Craton, detached during the Mesozoic Qinling orogeny and displaced about 100 km north from its original location. This suggests that the Taihua Group became part of the tectonic terrane associated with the Qinling orogeny and now forms part of the overthrust basement section of the Qinling belt. Before the Qinling orogeny, the Taihua Group was metamorphosed at 2.1 Ga. The initial Hf-isotope compositions of zircons, together with positive εNd(t) values for the whole-rocks, imply that the original magmas were derived from a juvenile source with some assimilation of an Archean crustal component.