Tectonic evolution of the eastern Central Asian Orogenic Belt: Evidence from zircon U-Pb-Hf isotopes and geochemistry of early Paleozoic rocks in Yanbian region, NE China
Tectonic evolution of the eastern Central Asian Orogenic Belt: Evidence from zircon U-Pb-Hf isotopes and geochemistry of early Paleozoic rocks in Yanbian region, NE China
复制标题
中亚造山带东部构造演化：延边地区早古生代岩石锆石U-Pb-Hf同位素和地球化学证据
DOI：
10.1016/j.gr.2016.01.004
复制
发表时间：
2016
影响因子：
6.1
通讯作者：
Ying Zhang
中科院分区：
文献类型：
--
作者：
Zhi-Wei Wang;Fu-Ping Pei;Wen-Liang Xu;Hua-Hua Cao;Zi-Jin Wang;Ying Zhang
本文首次提出了中国东北延边地区南部早古生代火山岩的证据。利用LA-ICP-MS锆石U-Pb和Hf同位素技术，对早古生代江渝群中的1块斜长片麻岩和2块含石榴子石的二云母石英片岩，以及侵入江渝群的2块英云闪长岩进行了分析。英云闪长岩的206 Pb/238 U锆石结晶年龄加权平均值分别为423和422 Ma。江峪群片麻岩和两个片岩样品中的锆石最大沉积年龄分别为439 ± 4、443 ± 2和443 ± 5 Ma。结合英云闪长岩侵入体的时代，这些制约因素表明江峪群的沉积时代为443 ~ 423 Ma（即，志留纪）。此外，三个江渝群样品的碎屑锆石年龄谱在442、473、513、565、600、635、671、740、1000和1162 Ma处有明显的年龄峰，在1344 ~ 3329 Ma处有次峰。江渝群中、新元古代碎屑锆石年龄群的出现，结合相应的锆石Hf同位素数据，揭示了江渝地体与冈瓦纳大陆东北部具有构造亲缘关系。中钾钙碱性I型英云闪长岩侵入体和江峪群碎屑锆石年龄谱表明，早古生代岩浆活动与中亚造山带东缘沿着同时代的俯冲-增生事件相对应。因此，我们认为江峪群是冈瓦纳大陆东北部裂陷、向北漂移并最终在早寒武世之后参与东大洋南缘早古生代构造演化的奇异地体的一部分。
We present the first evidence of an early Paleozoic terrane in the southern Yanbian region, NE China. We used LA-ICP-MS zircon U–Pb and Hf isotope techniques to analyze one plagioclase gneiss and two garnet-bearing two-mica quartz schists from the early Paleozoic Jiangyu Group, as well as two tonalites that intruded the Jiangyu Group. The tonalites yield weighted mean206Pb/238U zircon crystallization ages of 423 and 422 Ma. Zircons from the Jiangyu Group gneiss and two schist samples yield maximum depositional ages of 439 ± 4, 443 ± 2, and 443 ± 5 Ma, respectively. These constraints, together with the age of the tonalite intrusion, indicate that the Jiangyu Group was deposited between 443 and 423 Ma (i.e., Silurian). In addition, detrital zircon age spectra of the three Jiangyu Group samples exhibit prominent age peaks at 442, 473, 513, 565, 600, 635, 671, 740, 1000, and 1162 Ma, as well as secondary peaks between 1344 and 3329 Ma. The occurrence of the prominent Meso- and Neoproterozoic detrital zircon age populations for the Jiangyu Group, combined with the corresponding zircon Hf isotopic data, reveals that the Jiangyu Terrane has a tectonic affinity with northeastern Gondwana. The early Paleozoic magmatism, as suggested by the medium-K calc-alkaline I-type tonalite intrusion and Jiangyu Group detrital zircon age spectra, corresponds to coeval subduction–accretion events along the southern margin of the eastern Central Asian Orogenic Belt (CAOB). Accordingly, we propose that the Jiangyu Group is part of an exotic terrane that rifted from northeastern Gondwana, drifted northward, and ultimately became involved in the early Paleozoic tectonic evolution of the southern margin of the eastern CAOB after the Early Cambrian.