Petrogenesis and tectonic implications of the 2.1–2.0 Ga granitoids in Fuping Complex, North China Craton: Constraints from petrology, geochemistry and zircon U-Pb-Hf isotopes
Petrogenesis and tectonic implications of the 2.1–2.0 Ga granitoids in Fuping Complex, North China Craton: Constraints from petrology, geochemistry and zircon U-Pb-Hf isotopes
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DOI：
10.1016/j.precamres.2020.105611
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发表时间：
2020-04
影响因子：
3.8
通讯作者：
Jianlong Wang;Chonghui Yang;D. Wyman;Hui-xia Song;L. Du
中科院分区：
文献类型：
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作者：
Jianlong Wang;Chonghui Yang;D. Wyman;Hui-xia Song;L. Du
跨华北造山带（TNCO）中古元古代（2.2 ~ 2.0 Ga）岩浆活动对整个华北克拉通（NCC）古元古代地质演化具有重要意义。本文给出了TNCO富平杂岩2.1 ~ 2.0 Ga花岗岩类的地球化学、SHRIMP锆石U-Pb和Hf同位素资料。其中南营花岗质片麻岩的年龄分别为2075±13 Ma、2079±9 Ma和2073±10 Ma，岗南花岗质片麻岩的年龄分别为2081±8 Ma、2082±14 Ma和2063±7 Ma，白杨岭花岗岩体的年龄分别为2077±6 Ma、2070±19 Ma和2069±12 Ma，上庄花岗岩体的年龄分别为2072±12 Ma和2070±12 Ma。富平杂岩2.1 ~ 2.0 Ga花岗岩富集SiO2、K2O + Na2O、稀土元素（Eu除外）和高场强元素Zr、Nb、Ga、Y，贫CaO、al2o3、sr， Ga/Al比值高，Zr + Nb + Y + Ce绝对含量高，平均Zr饱和温度高达890℃，符合a型花岗岩的特征。所有样品中锆石的εHf(t)值均远低于同阶段贫化地幔的εHf(t)值，而Hf模型tdm1、tdmc1的年龄分别在2.3 ~ 2.7 Ga和2.4 ~ 2.9 Ga之间，远高于花岗岩类的年龄。这些锆石Hf模式年龄与富平杂岩新太古代TTG （tonalite - tronhjem -花岗闪长岩）片麻岩相似。综合岩石学、地球化学和同位素特征，推测富平杂岩体中这4个2.1 ~ 2.0 Ga花岗质岩体为新太古代TTG片麻岩的部分熔体，形成于拉张环境。大量资料表明，富平杂岩体中2.1 ~ 2.0 Ga a型花岗岩与基性岩脉为双峰岩浆组合。结合同期沉积的甘桃河群沉积岩，推断TNCO富平杂岩的2.1 ~ 2.0 Ga a型花岗岩的侵位于北陆构造带的陆内裂谷环境。这一证据表明华北克拉通在新太古代末期开始稳定。
Mid-Paleoproterozoic (2.2–2.0 Ga) magmatism in the Trans-North China Orogen (TNCO) is of great significance for the Paleoproterozoic geological evolution of the entire North China Craton (NCC). In this paper, we present geochemical, SHRIMP zircon U-Pb and Hf isotopic data on the 2.1–2.0 Ga granitoids in the Fuping Complex of the TNCO. These include the Nanying granitic gneiss, which yielded ages of 2075 ± 13 Ma, 2079 ± 9 Ma and 2073 ± 10 Ma, the Gangnan granitic gneiss, dated at 2081 ± 8 Ma, 2082 ± 14 Ma and 2063 ± 7 Ma, the Baiyangling granite with ages of 2077 ± 6 Ma, 2070 ± 19 Ma and 2069 ± 12 Ma, and the Shangzhuang granite, which yielded ages of 2072 ± 12 Ma and 2070 ± 12 Ma. The 2.1–2.0 Ga granitic rocks in Fuping Complex are enriched in SiO2, K2O + Na2O, rare earth elements (REEs) (except Eu), high field strength elements like Zr, Nb, Ga and Y, and depleted in CaO, Al2O3and Sr. Their Ga/Al ratios and absolute Zr + Nb + Y + Ce contents are high and their average Zr saturation temperatures are as high as 890 °C, all of which are consistent with the features of A-type granite. The εHf(t) values of zircon in all samples are much lower than that of the depleted mantle at the same stage, while Hf modelTDM1,TDMCages have ranges of 2.3–2.7 Ga and 2.4–2.9 Ga, respectively, which are much older than the age of the granitoids. These zircon Hf model ages are similar to those of the Neoarchean TTG (Tonalite-Trondhjemite-Granodiorite) gneisses in the Fuping Complex. Therefore, based on a combination of petrology, geochemistry and isotopic characteristics, we infer that these four 2.1–2.0 Ga granitic plutons in the Fuping Complex are partial melts of the Neoarchean TTG gneiss generated in an extensional environment. Based on extensive data, the 2.1–2.0 Ga A-type granites and the mafic dikes in the Fuping Complex represent a bimodal magma association. Considering the sedimentary rocks of the Gantaohe Group, deposited in the same period, we deduce that the 2.1–2.0 Ga A-type granite in the TNCO Fuping Complex was emplaced in an intra-continental rift setting in the NCC. This evidence indicates that the North China Craton was initially stabilized at the end of the Neoarchean.