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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| Institution: | 1. Key Laboratory of Orogenic Belts and Crustal Evolution, Ministry of Education, School of Earth and Space Sciences, Peking University, Beijing 100871, PR China;2. Department of Natural Resources of Hebei Province (Ocean Administration), Shijiazhuang 050000, PR China;1. Beijing Institute of Geology for Mineral Resources, Beijing 100012, PR China;2. Key Laboratory of Orogenic Belts and Crustal Evolution, Ministry of Education, Peking University, Beijing 100871, PR China;3. Department of Energy and Mineral Engineering, The Pennsylvania State University, College Park, PA 16802, USA;4. School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, PR China;5. Department of Geology, School of Resources and Civil Engineering, Northeastern University, Shenyang 110819, PR China;6. Research Institute of Petroleum Exploration & Development, PetroChina Liaohe Oilfield Company, Panjin 124000, PR China;1. Beijing SHRIMP Centre, Chinese Academy of Geological Sciences, 26 Baiwanzhuang Road, 100037 Beijing, China;2. Department of Geosciences, University of Mainz, D-55099 Mainz, Germany |
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| Abstract: | 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)N are 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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