Petrology and Geochemistry of the Huangshan Granitic Intrusion in Anhui Province, Southeast China: Implications for Petrogenesis and Geodynamics |
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| Authors: | ZHANG Shu ZHANG Zhaochong |
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| Institution: | State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences Beijing 100083, China |
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| Abstract: | The Huangshan granitic intrusion in Anhui province, SE China, is tectonically located at the southeastern boundary of the Yangtze Block. Based on the contact relation and the petrography, the Huangshan granitic intrusion can be divided into four stages, from early to late, medium-grained monzogranite, coarse-grained porphyric granite, fine-medium grained porphyric granite, and fine coarse grained granite. All rocks from the Huangshan granitic intrusion display similar petrological and geochemical characteristics, i.e. relatively high SiO2(>75%) and alkali (7.85%-8.59%), low CaO (<1%), high Fe-number (FeOT/(MgO+FeOT) = 0.93-0.97) and A1/CNK (atomic A1/(Ca+Na+K)) = 1.04-1.19. They are also enriched in rare earth elements (REE, except for Eu, with a total REE contents ranging from 116 ppm to 421 ppm), high strength field elements such as Zr, Hf, Nb, but depleted in Ba, Sr and Ni. The 10 000xGa/A1 ratios are higher than 2.6, which are consistent with the A-type granitoids. Based on the classification diagrams proposed by Eby, the Huangshan granite can be classified into the A2 group, which is usually believed to be formed under an extensional tectonic setting. Their Nd isotopic compositions suggest that the primary magmas of the Huangshan granite are predominantly derived from the Proterozoic andesitic rocks in the region, and this conclusion is also supported by REE modeling. The systemic investigations on the geochemistry of the Huangshan granitic intrusion can provide significant implications for the understanding of the petrogenesis and the geodynamic regime of southeastern China during the Late-Mesozoic. |
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| Keywords: | Huangshan granitic intrusion A-type granitoids geochemistry Late-Mesozoic lithospheric extension |
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