Geochronology and geochemistry of early Paleozoic igneous rocks of the Lesser Xing'an Range, NE China: Implications for the tectonic evolution of the eastern Central Asian Orogenic Belt
Geochronology and geochemistry of early Paleozoic igneous rocks of the Lesser Xing'an Range, NE China: Implications for the tectonic evolution of the eastern Central Asian Orogenic Belt
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小兴安岭早古生代火成岩年代学和地球化学：对中亚造山带东部构造演化的启示
DOI：
10.1016/j.lithos.2015.11.006
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发表时间：
2015
期刊：
影响因子：
3.5
通讯作者：
Peng Guo
中科院分区：
文献类型：
--
作者：
Zhi-wei Wang;Wen-liang Xu;Fu-ping Pei;Feng Wang;Peng Guo
本文通过对小兴安岭早古生代火成岩锆石U-Pb、Hf同位素及全岩常量、微量元素的研究，探讨了中亚造山带东部早古生代构造演化的规律。锆石U-Pb定年表明，松嫩-张广才地块北方早古生代岩浆活动可划分为4个阶段：中寒武世（~ 505 Ma）、晚寒武世（~ 490 Ma）、早-中奥陶世（~ 470 Ma）和晚奥陶世（~ 460-450 Ma）。中寒武世二长花岗岩富钾、弱-强过铝质，具有明显的重稀土元素（HREE）亏损、高Sr/Y比值、低Y浓度、低原生锆石εHf（t）值（− 6.79 ~ − 1.09）和古老的两阶段模式（TDM 2）年龄（1901-1534 Ma）等特征。这些结果表明，部分熔融增厚的古地壳物质形成的北方SZM和北方佳木斯地块（JM）的合并。晚寒武世二长岩、石英二长岩和二长花岗岩单元的化学成分与A型花岗岩相似，含锆石，εHf（t）值为− 2.59 ~+ 1.78，TDM 2年龄为1625-1348 Ma。我们推断，这些岩石形成的原生岩浆部分熔融所产生的中元古代增生的下地壳物质在后碰撞拉伸环境。早-中奥陶世石英二长闪长岩、石英二长岩、二长花岗岩和流纹岩单元为钙碱性，相对富集轻稀土元素（LREE）和大离子亲石元素（LILE），Rb、Th和U），贫HREE和高场强元素（HFSE;例如，Nb、Ta和Ti），并含有εHf（t）值为− 7.33至+4.98的锆石，表明形成于活动大陆边缘环境。晚奥陶世碱长花岗岩和流纹岩单元具有A型花岗岩的亲缘关系，表明它们形成于伸展环境。通过对北方SZM和JM早古生代岩浆事件和Hf同位素模式年龄的对比，表明尽管SZM所含的地壳物质比JM古老得多，但两者具有相似的中元古代和早古生代地壳增生改造历史。
This paper presents new zircon U–Pb, Hf isotope, and whole-rock major and trace element data for early Paleozoic igneous rocks of the Lesser Xing'an Range, NE China, in order to constrain the early Paleozoic tectonic evolution of the eastern Central Asian Orogenic Belt (CAOB). Zircon U–Pb dating indicates that early Paleozoic magmatic events within the northern Songnen–Zhangguangcai Range Massif (SZM) can be subdivided into four stages: Middle Cambrian (~ 505 Ma), Late Cambrian (~ 490 Ma), Early–Middle Ordovician (~ 470 Ma), and Late Ordovician (460–450 Ma). The Middle Cambrian monzogranites are K-rich, weakly to strongly peraluminous, and characterized by pronounced heavy rare earth element (HREE) depletions, high Sr/Y ratios, low Y concentrations, low primary zircon εHf(t) values (− 6.79 to − 1.09), and ancient two-stage model (TDM2) ages (1901–1534 Ma). These results indicate derivation from partial melting of thickened ancient crustal materials that formed during the amalgamation of the northern SZM and the northern Jiamusi Massif (JM). The Late Cambrian monzonite, quartz monzonite, and monzogranite units are chemically similar to A-type granites, and contain zircons with εHf(t) values of − 2.59 to + 1.78 and TDM2ages of 1625–1348 Ma. We infer that these rocks formed from primary magmas generated by partial melting of Mesoproterozoic accreted lower crustal materials in a post-collisional extensional environment. The Early–Middle Ordovician quartz monzodiorite, quartz monzonite, monzogranite, and rhyolite units are calc-alkaline, relatively enriched in light REEs (LREEs) and large ion lithophile elements (LILEs; e.g., Rb, Th, and U), depleted in HREEs and high field strength elements (HFSEs; e.g., Nb, Ta, and Ti), and contain zircons with εHf(t) values of − 7.33 to + 4.98, indicative of formation in an active continental margin setting. The Late Ordovician alkali-feldspar granite and rhyolite units have A-type granite affinities that suggest they formed in an extensional environment. A comparison of early Paleozoic magmatic events and Hf isotopic model ages between the northern SZM and the JM indicates that these two massifs have similar histories of Mesoproterozoic and early Paleozoic crustal accretion and reworking, although the SZM contains much older crustal materials than the JM.