Diversity of late Neoarchean K-rich granitoid rocks derived from subduction-related crust/mantle interactions in the Jiaobei terrane, North China Craton
Diversity of late Neoarchean K-rich granitoid rocks derived from subduction-related crust/mantle interactions in the Jiaobei terrane, North China Craton
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华北克拉通胶北地体俯冲作用衍生的新太古代晚期富钾花岗岩的多样性
DOI：
10.1016/j.gr.2020.03.008
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发表时间：
2020-09
影响因子：
6.1
通讯作者：
Lishuang Guo
中科院分区：
文献类型：
--
作者：
Denggang Lu;Wei Wang;Shuwen Liu;Peter A. Cawood;Jiachen Yao;Pengbo Niu;Lishuang Guo
在几乎所有的古克拉通中，大量富钾花岗岩的出现代表了晚太古宙地球的一大特征，这是理解这一时期全球过渡地球动力学体制的关键。不同富钾花岗岩类之间的成因机制和联系以及它们对地壳生长和演化的影响仍然存在争议。中国克拉通北部胶北地体中产出一系列新太古代晚期富钾花岗岩类，包括石英闪长岩、花岗闪长岩和二长花岗岩。石英闪长-花岗闪长质片麻岩为镁质岩石，具有低硅、低钛、高K、高镁的特征，与太古宙低钛三长花岗岩相似。Sr/Y和(La/Yb)N值较高(大多为59.99-119.32和8.56-61.42)，Nb中等偏高(最高可达11.79ppm)。地球化学模拟结合亏损锆石εHf(T2)(+0.5h−+7.2.)和少量包裹体锆石的存在，表明这些低二氧化硅样品来自交代亏损地幔源区，板片流体和熔体的输入，以及古代地壳物质的少量混染。二长花岗岩为富硅、高钾、高铁、低镁的铁质岩石。它们分为两个亚组：第一组显示44.00-127.00 ppm的低树和正Eu异常(EUN/Eu*N=91.06-1.6)；第二组显示高树85.76-819.02 ppm但Eu负异常(Eun/Eu*N=90.51-0.62)。地球化学模拟和亏损锆石εHf(T2)+2.6t/−+8.4时表明，它们是由不同地壳水平的英云闪长岩和一些变质沉积岩的年轻壳源部分熔融形成的。结合区域地质资料，这些晚太古代富钾花岗岩是在地壳稳定化过程中交代亏损地幔和以年轻地壳物质为主的耦合熔融形成的。此外，胶北地体在俯冲-吸积环境下经历了约2.6-2.5t Ga的地壳生长。
The appearance of voluminous K-rich granitoids within nearly all ancient cratons represents one major characteristic of late Archean Earth, which hold the key to understand the transitional geodynamic regimes globally during this period. The genetic regimes and links among different K-rich granitoids and their implications for crustal growth and evolution remain controversial. A series of late Neoarchean K-rich granitoids, including quartz dioritic, granodioritic, and monzogranitic gneisses, occur in the Jiaobei terrane of North China Craton. Zircon U-Pb isotopic data reveal that they emplaced during ~2544–2494 Ma, coeval with regional ~2530–2470 Ma high-grade metamorphism.The quartz dioritic-granodioritic gneisses are magnesian rocks, and they show low Si and Ti, but high K and Mg, similar to Archean low-Ti sanukitoids. The Sr/Y and (La/Yb)Nare high (mostly 59.99–119.32 and 8.56–61.42), with moderate to high Nb (up to 11.79 ppm). Geochemical modeling, combined with depleted zircon εHf(t2) (+0.5 − +7.2) and the presence of minor xenocrystic zircons, indicate that these low silica samples were derived from a metasomatized depleted mantle source with inputs of slab-derived fluids and melts, and minor contamination by ancient crustal materials. The monzogranitic rocks are ferroan rocks showing high Si, K, and Fe, but low Mg. They are divided into two subgroups: the first displays low TREE of 44.00–127.00 ppm and positive Eu anomalies (EuN/Eu*N= 1.06–1.60), whereas the second shows high TREE of 85.76–819.02 ppm but negative Eu anomalies (EuN/Eu*N= 0.51–0.62). Geochemical modeling and depleted zircon εHf(t2) of +2.6 − +8.4 suggest their formation by partial melting of juvenile crustal sources involving tonalitic and some metasedimentary rocks at diverse crustal levels.Combined with regional geological data, these late Neoarchean K-rich granitoids were generated by coupled melting of metasomatized depleted mantle and dominantly juvenile crustal materials during crustal stabilization. Furthermore, the Jiaobei terrane experienced ~2.6–2.5 Ga crustal growth under a subduction-accretion setting.
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