Mesozoic magmatism in the eastern North China Craton: Insights on tectonic cycles associated with progressive craton destruction
Mesozoic magmatism in the eastern North China Craton: Insights on tectonic cycles associated with progressive craton destruction
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DOI：
10.1016/j.gr.2018.04.003
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发表时间：
2018-08
影响因子：
6.1
通讯作者：
Fan Yang;M. Santosh;Sung‐Won Kim
中科院分区：
文献类型：
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作者：
Fan Yang;M. Santosh;Sung‐Won Kim
华北克拉通（NCC）提供了一个典型的例子，岩石圈减薄与克拉通破坏（或去克拉通化）通过多个构造事件。克拉通的破坏高峰期主要发生在中生代，特别是早白垩世，南部与三叠纪华北克拉通与扬子克拉通的俯冲/碰撞有关，东部与早白垩世古太平洋板块的俯冲有关。本文通过对沂水和莒县南域一套花岗岩、辉长岩、闪长岩、玄武岩、安山岩、火山凝灰岩、集块岩、硅质凝灰岩和粗面岩等侵入岩和火山岩的研究，探讨了华北克拉通东部中生代构造演化与去克拉通作用的关系。玄武岩中锆石U-Pb数据显示出多个具有捕虏晶颗粒的群体，其年龄范围从古元古代（2457-1940 Ma），到新元古代（896-559 Ma），到古生代（442-380 Ma）和中生代（204-122 Ma）。花岗岩和辉长岩的继承性颗粒的206 Pb/238 U产额重平均年龄为650.0 ± 13 ~ 773.4 ± 2.6Ma，表明有来自扬子板块的组分参与。闪长岩中岩浆锆石206 Pb/238 U重量平均年龄为121.5 ± 1.2Ma，代表了该岩石的侵位年龄。火山岩套（安山岩、火山凝灰岩、集块岩、硅质凝灰岩和粗面岩）中的岩浆锆石颗粒加权平均206 Pb/238 U年龄分别为132.4 ± 1.4 Ma、123.02 ± 0.71 Ma、122.97 ± 0.69 Ma、121.96 ± 0.49 Ma和124.6 ± 1.1 Ma，与它们的喷发时间相对应。古元古代的锆石颗粒对应于捕虏晶，而新元古代和古生代的锆石颗粒则继承自扬子地台。晚三叠世-侏罗纪锆石颗粒与扬子陆壳深俯冲及华北克拉通-扬子板块陆-陆碰撞过程中增厚的陆壳拆沉作用有关。早白垩世的人口可以联系到古太平洋板块俯冲从东部和相关的伸展环境。地球化学数据显示，本区轻稀土元素明显富集，沿着伴有Eu负异常，Th/Ta、La/Nb比值高，Nb-Ta负异常，大离子亲石元素（K、Rb、Ba、Pb）的富集程度高于高场强元素（Nb、Ta、Ti）的富集程度，反映了活动大陆边缘俯冲弧岩浆环境。这些岩石的锆石Lu-Hf数据显示εHf（t）值为负，范围为-36.8 ~-3.1，TDM值为1105-2572 Ma，TDMC值为1785 ~ 3776 Ma。表明岩浆源区包括古元古代组分，少量太古宙地壳改造的输入，通过不同程度的地壳物质富集和少量的伸展输入-相关的地幔熔融。结合前人在华北克拉通东部的研究结果，我们认为晚古生代古亚洲洋向南俯冲、三叠纪扬子板块向北俯冲并与华北克拉通碰撞、早白垩世古太平洋板块向西俯冲共同促成了华北克拉通的破坏。古太平洋板块俯冲到NCC之下（主要贡献机制），板片回滚引起的岩石圈伸展可能促进了弧后扩张，软流圈上涌导致岩石圈减薄，包括拆沉、岩石圈地幔熔融和下地壳下的改性地幔底侵。
The North China Craton (NCC) provides a classic example for lithospheric thinning associated with craton destruction (or decratonization) through multiple tectonic events. The peak of craton destruction is considered to have occurred during Mesozoic, especially in Early Cretaceous, linked to the subduction/collision between the NCC and Yangtze Craton during the Triassic in the south and the Paleo-Pacific plate subduction during Early Cretaceous in the east. Here we investigate a suite of intrusive and volcanic suites including granite, gabbro, diorite, basalt, andesite, volcanic tuff, agglomerate, siliceous tuff and trachyte from the southern Yishui and Juxian domains to gain insights into the Mesozoic tectonic evolution of the eastern NCC in relation to decratonization. Zircon U-Pb data from basalt show multiple populations with xenocrystic grains ranging in age from Paleoproterozoic (2457–1940 Ma), through Neoproterozoic (896–559 Ma), to Paleozoic (442–380 Ma) and Mesozoic (204–122 Ma). Inherited grains from the granite and gabbro yield weight mean206Pb/238U ages of 650.0 ± 13 to 773.4 ± 2.6 Ma suggesting the involvement of components from the Yangtze Craton. Magmatic zircons from diorite show weight mean206Pb/238U ages of 121.5 ± 1.2 Ma representing the emplacement age of this rock. Magmatic zircon grains from the volcanic suite (andesite, volcanic tuff, agglomerate, siliceous tuff and trachyte), show weighted mean206Pb/238U ages of 132.4 ± 1.4 Ma, 123.02 ± 0.71 Ma, 122.97 ± 0.69 Ma, 121.96 ± 0.49 Ma, and 124.6 ± 1.1 Ma respectively, corresponding to the timings of their eruption. The Paleoproterozoic zircon grains correspond to xenocrysts captured from the NCC basement rocks, whereas the Neoproterozoic and Paleozoic grains were inherited from the Yangtze Craton. The Late Triassic to Jurassic zircon grains can be correlated to delamination of the thickened continental crust during deep subduction of Yangtze continental crust and the continent-continent collision between NCC and the Yangtze Craton. The Early Cretaceous population can be linked to the subduction of the Paleo-Pacific plate from the east and related extensional setting. The geochemical data display significant enrichment in LREE along with negative Eu anomalies, with high Th/Ta and La/Nb ratios, negative Nb–Ta anomalies, and high concentration of LILE (K, Rb, Ba and Pb) than HFSE (Nb, Ta and Ti), suggesting subduction-related arc magmatic setting in an active continental margin. Zircon Lu-Hf data from these rocks display dominantly negative εHf(t) values ranging from −36.8 to −3.1, TDMin the range of 1105–2572 Ma, and TDMCbetween 1785 Ma and 3776 Ma, indicating that the magma sources involved Paleoproterozoic components with minor input of reworked Archean crust through different degrees of enrichment with crustal material and minor input from extension-related mantle melting. In conjunction with the results from previous studies in the eastern NCC, we propose that the late Paleozoic southward subduction of the Paleo-Asian Ocean, the Triassic northward subduction and collision of the Yangtze Craton with the NCC, and the Early Cretaceous westward subduction of the Paleo-Pacific plate jointly contributed to the cratonic destruction of NCC. The Paleo-Pacific plate subduction beneath the NCC (major contributing mechanism) with the slab rollback induced lithospheric extension likely facilitated back-arc spreading, asthenospheric upwelling resulting in lithospheric thinning including delamination, melting of lithosphere mantle, and underplating of the modified mantle beneath the lower crust of …