Zircon U-Pb Age,Geochemical,and Sr-Nd-Pb-Hf Isotopic Constraints on the Time Frame and Origin of Early Cretaceous Mafic Dykes in the Wuling Mountain Gravity Lineament,South China
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Zircon U-Pb Age,Geochemical,and Sr-Nd-Pb-Hf Isotopic Constraints on the Time Frame and Origin of Early Cretaceous Mafic Dykes in the Wuling Mountain Gravity Lineament,South China
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The authors thank Dr.Yang Shuqin for assistance during the XRF analyses,Prof. Qi Liang and Li Xiaobiao for assistance during ICP-MS analyses,the technician for assistance during TIMS Sr–Nd–Pb isotopic analyses,and Profs. Xiaoming Liu and Honglin Yuan for assistance during LA-ICP-MS U-Pb dating and Hf isotopic analyses. This study was supported by the National Natural Science Foundation of China (grant, 41573022).

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    In view of the importance of mafic dyke swarms and their contribution to current scientific problems relating to South China,herein,we present the findings of studies on twenty–five representative mafic dykes cropping out in Hunan Province and Guangxi Zhuang Autonomous Region,within the southern Wuling Mountain gravity lineament,China.These results include new zircon LA-ICP-MS U-Pb age,whole rock geochemical,Sr-Nd-Pb isotopic,and zircon Hf isotopic data for these dykes.The dykes formed between 131.5 ± 1.2 and 121.6 ± 1.1 Ma,and have typical doleritic textures.They fall into the alkaline and shoshonitic series,are enriched in light rare earth elements (LREE),some large ion lithophile elements (LILE;e.g.,Rb,Ba,and Sr),Th,U,and Pb,and are depleted in Nb,Ta,Hf,and Ti.Moreover,the dolerites have high initial 87Sr/86Sr ratios(0.7055–0.7057),negativeεNd(t) and zircon εHf(t) values(?14.8 to ?11.9,?30.4 to ?14.9),and relatively constant initial Pb isotopic ratios (that are EM1-like,16.77–16.94,15.43–15.47,and 36.84–36.92 for 206Pb/204Pb,207Pb/204Pb,and 208Pb/204Pb,respectively).These results indicate that the dykes were likely derived from magma generated through low-degree partial melting (1.0%–10%) of an EM1-like garnet–lherzolite mantle source.The parental magmas fractionated olivine,clinopyroxene,plagioclase,and Ti-bearing phases with negligible crustal contamination,during ascent and dyke emplacement.Several possible models have been proposed to explain the origin of Mesozoic magmatism along the Wuling Mountain gravity lineament.Herein we propose a reasonable model for the origin of these mafic dykes,involving the collision between the paleo-Pacific Plate and South China,which led to subsequent lithospheric extension and asthenosphere upwelling,resulting in partial melting the underlying mantle lithosphere in the Early Cretaceous,to form the parental magmas to the WMGL mafic dykes,as studied.

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CHEN Xiaoqing, LIU Shen, FENG Caixia, XU Jingyan, ZHAO Huibo, FENG Guangying, Ian M. COULSON, SUN Jinggui, FAN Yan.2021. Zircon U-Pb Age, Geochemical, and Sr-Nd-Pb-Hf Isotopic Constraints on the Time Frame and Origin of Early Cretaceous Mafic Dykes in the Wuling Mountain Gravity Lineament, South China[J]. ACTA GEOLOGICA SINICA(English edition),95(2):419~438

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  • 收稿日期:2019-05-28
  • 最后修改日期:2020-01-02
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  • 在线发布日期: 2021-04-27
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