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Early Cretaceous granitoids and gabbro in the Liaodong Peninsula: implications for delamination of the North China Craton and Paleo-Pacific Plate subduction
Mineralogy and Petrology ( IF 1.8 ) Pub Date : 2021-02-18 , DOI: 10.1007/s00710-020-00735-7
Jinyu Li , Ye Qian , Jinlei Sun , Haoran Li , Changji Zhao , Fengyue Sun , Yanjie Shen

New petrological, whole-rock geochemical, zircon U–Pb geochronological, and zircon Lu–Hf isotopic data have been reported for Early Cretaceous intrusive rocks in the Wulong region of the Liaodong Peninsula on the North China Craton. The zircon U-Pb chronology shows that the crystallization age of six groups of intrusive rocks from this region is 129–123 Myr ago. These intrusive rocks can be categorized into A-type granite (granodiorite), K-rich adakite (porphyritic-like monzogranite), highly fractionated I-type granites (porphyritic-like biotite monzogranite, porphyritic-like syenogranite, and syenogranite), and gabbro. These granitoids are shown to have negative zircon εHf(t) values(-21.0 to -11.1) with old two-stage Hf model ages (TDM2(Hf)) (1.88–2.50 Ga), while gabbro has higher zircon εHf(t) values(-14.3 to -9.4) with younger TDM2(Hf) (1.77–2.08 Ga) model ages. According to our results, we believe that the porphyritic-like monzogranite was produced through partial melting of the thickened eclogitic lower crust, the gabbro was generated by partial melting of a source formed by the mixing of enriched lithospheric mantle and delaminated eclogitic lower crust, the granodiorite was formed by mixing crust materials and mafic melts, the porphyritic-like biotite monzogranite, porphyritic-like syenogranite, and syenogranite originated from the medium- to high-K basaltic lower crust. The bimodal intrusive rocks (gabbro, porphyritic-like monzogranite, and porphyritic-like biotite monzogranite) and A-type granites (granodiorite) were emplaced in an extensional setting associated with Paleo-Pacific Plate subduction. We also determined that the tectonic setting changed from extension to transpression during 125–120 Myr ago (porphyritic-like syenogranite and syenogranite). Moreover, we confirmed the hypothesis that the Early Cretaceous delamination is the result of Paleo-Pacific Plate subduction.



中文翻译:

辽东半岛早白垩世花岗岩和辉长岩:对华北克拉通和古太平洋板块俯冲作用的分层作用

华北克拉通辽东半岛武隆地区早白垩世侵入岩已有新的岩石学,全岩石地球化学,锆石U-Pb年代学和锆石Lu-Hf同位素数据。锆石的U-Pb年表显示,该地区六组侵入岩的结晶年龄为129-123 Myr以前。这些侵入性岩石可分为A型花岗岩(闪长闪长岩),富K的红柱石(斑状样蒙脱石),高分度I型花岗岩(斑状类黑云母,辉长岩,斑状类辉长岩和正辉长岩)和辉长岩。这些花岗石显示具有负的锆石εHf(t)值(-21.0至-11.1),且具有两阶段的旧Hf模型年龄(T DM2(Hf))(1.88–2.50 Ga),而辉长岩具有较高的锆石εHf(t)值(-14.3至-9.4),且T DM2较年轻(Hf)(1.77–2.08 Ga)模型年龄。根据我们的结果,我们认为斑状类辉长花岗岩是通过部分熔融增厚的弧面下地壳部分熔融而产生的,辉长岩是通过部分熔融富集岩石圈地幔和分层弧面下地壳而形成的源而产生的。花岗闪长岩是由地壳物质和铁镁质熔体混合而成的,斑状样黑云母辉长花岗岩,斑状样正长花岗岩和正长花岗岩起源于中-高钾玄武岩下地壳。在与古太平洋板块俯冲有关的伸展背景下,将双峰侵入岩(辉闪岩,斑状样辉长岩和斑岩状黑云母辉长岩)和A型花岗岩(闪长闪长岩)置于其中。我们还确定,在125-120 Myr以前,构造背景从延伸转变为压抑(斑状类正长花岗岩和正长花岗岩)。此外,我们证实了这样的假说,即早白垩世分层是古太平洋板块俯冲的结果。

更新日期:2021-02-18
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