Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8911730 | Lithos | 2018 | 49 Pages |
Abstract
Paleoproterozoic A-type granites are widely outcropped in the North China Craton (NCC), particularly in the Trans-North China Orogen. However, their genesis and tectonic significance remain obscure. Here we report systematic studies on geochronology and geochemical characteristics of A-type granite in Huayangchuan, south margin of the NCC. The samples are enriched in total alkali (K2Oâ¯+â¯Na2Oâ¯>â¯8.97â¯wt%), and depleted in MgO (0.84-0.93â¯wt%), CaO (1.28-1.90â¯wt%) and P2O5 (0.18-0.20â¯wt%), with high FeOT/MgO (5.69-6.67). They are characterized by high Zrâ¯+â¯Yâ¯+â¯Nbâ¯+â¯Ce values (1293-1392â¯ppm) and 10,000â¯Ãâ¯Ga/Al ratios (3.14-3.35), which are typical characteristics of A-type granite. The Huayangchuan A-type granite can be further classified as A1-type subgroup based on particular geochemical features, e.g., low Y/Nb (0.87-1.00) and Yb/Ta (0.88-1.10). High precision zircon U-Pb dating of the A-type granite by secondary ion mass spectrometry (SIMS) yields Paleoproterozoic 207Pb/206Pb ages of 1829.5â¯Â±â¯2.5â¯Ma. The low zircon ÉHf(t) values (â6.97 to â10.45), along with zircon Hf model age of 2.7-2.9â¯Ga, indicate that the Huayangchuan A-type granite was derived from partial melting of the ancient continental crust with contribution of enriched mantle components. The low zircon δ18O composition (4.00 to 6.78â°) indicates that the zircons were crystallized from low δ18O magmas, which derived from the crust metasomatized by low δ18O mantle fluids or melts. The E-W trend A1-type granitic plutons in the NCC are generally outcropped in a rift tectonic regime, which is consistent with the development of the mantle plume in the Xiong'er district. The large volume of basaltic magmas, generated by mantle plume head, underplated the lower continental crust and formed the Huayangchuan A-type granite.
Related Topics
Physical Sciences and Engineering
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Authors
Shuo Xue, Yang Xu, Ming-Xing Ling, Qing-Qing Kang, Xiao-Yan Jiang, Sai-Jun Sun, Kai Wu, Zhe-Kun Zhang, Ze-Bin Luo, Yu-Long Liu, Weidong Sun,