Neoarchean (2.5–2.8 Ga) crustal growth of the North China Craton revealed by zircon Hf isotope: A synthesis
Neoarchean (2.5–2.8 Ga) crustal growth of the North China Craton revealed by zircon Hf isotope: A synthesis
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DOI：
10.1016/j.gsf.2011.10.006
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发表时间：
2012-03
影响因子：
8.9
通讯作者：
An Wang;Yican Liu
中科院分区：
文献类型：
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作者：
An Wang;Yican Liu
华北陆块新太古代的地壳生长（2.5-2.8Ga）是一个有争议的话题，有人提出主要的地壳生长发生在新太古代晚期（2.5-2.6Ga），与岩浆作用的时间相一致，而其他人则认为主要的地壳增生发生在新太古代早期（2.7-2.8Ga），与世界上其它古陆的成壳时代一致。锆石U-Pb年龄和Hf同位素组成对华北克拉通的地壳生长时间、演化和构造分区具有严格的制约作用。本文综合评述了NCC各分区的锆石Hf同位素资料，结合锆石U-Pb年代学和地球化学资料，对NCC新太古代地壳生长进行了研究。结果表明，2.7-2.8Ga和2.5-2.6Ga的地壳生长都分布在NCC上，前者比以前提出的要宽得多。东部地块以2.7-2.8Ga的地壳生长为主，局部2.5-2.6Ga有新的地壳形成;阴山地块以2.7Ga的地壳增生为主。孔兹岩带碎屑锆石资料表明，西地块地壳生长的主要时期为古元古代，有少量早、中太古代地壳成分，华北造山带（TNCO）地壳增生的年龄范围为2.5 ~ 2.9Ga，区域差异明显。锆石Hf同位素组成，结合锆石年龄等地球化学资料，表明南陆缘可能不是TNCO的延伸，NCC的演化和构造分区比以前提出的更为复杂，可能涉及多阶段的地壳生长和俯冲过程。然而，2.7-2.8Ga岩浆活动和地壳形成的分布范围无疑比以前认为的要广，这一点得到了前寒武纪下地壳岩石、上覆沉积盖层、现代河流沉积物和晚新太古代正长花岗岩中锆石的进一步支持。
The crustal growth of the North China Craton (NCC) during the Neoarchean time (2.5–2.8Ga) is a hotly controversial topic, with some proposing that the main crustal growth occurred in the late Neoarchean (2.5–2.6Ga), in agreement with the time of the magmatism, whereas others suggest that the main crustal accretion took place during early Neoarchean time (2.7–2.8Ga), consistent with the time of crustal-formation of other cratons in the world. Zircon U-Pb ages and Hf isotope compositions can provide rigorous constraints on the time of crustal growth and the evolution and tectonic division of the NCC. In this contribution, we make a comprehensive review of zircon Hf isotope data in combination with zircon U-Pb geochronology and some geochemistry data from various divisions of the NCC with an aim to constrain the Neoarchean crustal growth of the NCC. The results suggest that both 2.7–2.8Ga and 2.5–2.6Ga crustal growth are distributed over the NCC and the former is much wider than previously suggested. The Eastern block is characterized by the main 2.7–2.8Ga crustal growth with local new crustal-formation at 2.5–2.6Ga, and the Yinshan block is characterized by ∼2.7Ga crustal accretion as revealed by Hf-isotope data of detrital zircons from the Zhaertai Group. Detrital zircon data of the Khondalite Belt indicate that the main crustal growth period of the Western block is Paleoproterozoic involving some ∼2.6Ga and minor Early- to Middle-Archean crustal components, and the crustal accretion in the Trans-North China Orogen (TNCO) has a wide age range from 2.5Ga to 2.9Ga with a notable regional discrepancy. Zircon Hf isotope compositions, coupled with zircon ages and other geochemical data suggest that the southern margin may not be an extension of the TNCO, and the evolution and tectonic division of the NCC is more complex than previously proposed, probably involving multi-stage crustal growth and subduction processes. However, there is no doubt that 2.7–2.8Ga magmatism and crustal-formation are more widely distributed than previously considered, which is further supported by the data of zircons from Precambrian lower crustal rocks, overlying sedimentary cover, modern river sediments and Late Neoarchean syenogranites.