Mesoproterozoic (~1.4 Ga) magmatism in the Liaoyuan Accretionary Belt, NE China: New implications for tectonic affinity and crustal evolution of microcontinents along the southern Central Asian Orogenic Belt
Mesoproterozoic (~1.4 Ga) magmatism in the Liaoyuan Accretionary Belt, NE China: New implications for tectonic affinity and crustal evolution of microcontinents along the southern Central Asian Orogenic Belt
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中国东北辽源增生带中元古代（~1.4 Ga）岩浆作用：对中亚造山带南部微大陆构造亲和性和地壳演化的新意义
DOI：
10.1016/j.precamres.2021.106389
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发表时间：
2021
影响因子：
3.8
通讯作者：
Yu Gao
中科院分区：
文献类型：
--
作者：
Changhai Li;Zhenghong Liu;Xiaojie Dong;Zhongyuan Xu;Kai Wen;Shijie Wang;Chen Wang;Yu Gao
在中亚造山带南缘的中、西部地区已发现了中元古代花岗质岩浆活动，而在东部地区则鲜有报道。在这项研究中，中元古界花岗质岩石被确定在辽源增生带（LAB），位于中国东北地区，在南部CAOB的东部。从这些样品中获得的信息可能会阐明目前对该地区前寒武纪演化的理解。5个花岗质岩石的锆石U-Pb加权平均年龄在1321 ± 43 ~ 1388 ± 31 Ma之间。这些样品的特征在于高SiO2（69.30- 77.51wt%）、MgO（1.96- 2.34wt%）、Fe 2 O3（3.48- 3.82wt%）和Cr（40-80 ppm）含量，中等Al 2 O3含量（11.23- 15.80wt%）和高Mg#值（45-56）。此外，它们富含轻稀土元素（LREE）、Zr和Hf，但贫含重稀土元素（HREE）、Nb、Ta和Ti。此外，它们还表现出明显的负Eu异常（Eu/Eu* = 0.25-0.84）。此外，样品具有较高的Zr + Ce + Y + Nb含量（300-497 ppm），表明与A型花岗岩有密切的亲缘关系。锆石的εHf（t）值为正值（3.31 ~ 11.1，平均值为7.5），两阶段模式年龄（TDM 2）为1480 ~ 2128 Ma。综合以上资料，认为本区中元古代花岗质岩石是年轻地壳部分熔融并加入幔源物质的产物。花岗岩侵位于俯冲洋板回滚或断裂的伸展环境。年轻的1.4 Ga花岗岩类岩石，像这些在LAB，也保存在其他微大陆沿着南部CAOB。它们的地球化学特征与劳伦提斯和波罗的海地区同期岩浆活动形成的岩石具有可比性，而与华北、塔里木和西伯利亚盆地的岩石不具有可比性。根据目前和以前的研究，保存的年轻的1.4 Ga岩石的微大陆可能属于大陆边缘的哥伦比亚超大陆，并显示与劳伦蒂亚-波罗的海的组合陆块构造的亲和力。
The Mesoproterozoic granitic magmatism has been identified in the middle and western part of the southern margin of Central Asian Orogenic Belt (CAOB), but rarely reported from the eastern part. In this study, Mesoproterozoic granitic rocks were identified in the Liaoyuan Accretionary Belt (LAB), an area located in the northeast China, within the eastern part of the southern CAOB. Information obtained from these samples is likely to elucidate the current understanding of the Precambrian evolution in this area. The five granitic rocks yielded zircon U–Pb weighted mean ages between 1321 ± 43 Ma and 1388 ± 31 Ma. These samples are characterized by high SiO2(69.30–77.51 wt%), MgO (1.96–2.34 wt%), Fe2O3(3.48–3.82 wt%), and Cr (40–80 ppm) contents, moderate Al2O3contents (11.23–15.80 wt%), and high Mg#values (45–56). Furthermore, they are rich in light rare earth elements (LREEs), Zr, and Hf, but depleted in heavy rare earth elements (HREEs), Nb, Ta, and Ti. Moreover, they also exhibit significant negative Eu anomalies (Eu/Eu* = 0.25–0.84). In addition, the samples have high Zr + Ce + Y + Nb contents (300–497 ppm) indicating A-type granite affinities. The zircons depicted positiveεHf(t) values (3.31 to 11.1, average value of 7.5) with two stage model ages (TDM2) varying from 1480 Ma to 2128 Ma. Based on the above data, it was concluded that the Mesoproterozoic granitic rocks in this area were derived from partial melting of juvenile crust with addition of mantle-derived materials. The granites were emplaced in an extensional setting caused by roll back or break off of subducted oceanic slab. Juvenile ∼ 1.4 Ga granitic rocks, like these in the LAB, were also preserved in other microcontinents along the southern CAOB. Their geochemical characteristics are comparable to rocks derived from contemporaneous igneous activity in Laurentia and Baltica, but not those in the North China, Tarim or the Siberian Cratons. Based on the present and previous studies, the microcontinents that preserved the juvenile ∼ 1.4 Ga rocks might belong to a continental terrane in the periphery of the Columbia supercontinent and show tectonic affinity with the combined Laurentia–Baltica landmass.