U-Pb Zircon Age,Geochemical, and Sr-Nd-Pb Isotopic Constraints on the Age and Origin of Mafic Dykes from Eastern Shandong Province,Eastern China |
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| Authors: | LIU Shen HU Ruizhong FENG Caixia GAO Shan FENG Guangying LAI Shaocong QI Youqiang Ian M COULSON YANG Yuhong YANG Chaogui and TANG Liang State |
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| Institution: | Key Laboratory of Continental Dynamics /Department of Geology, Northwest University 710069, China 2 State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China 3 State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China 4 Solid Earth Studies Laboratory, Department of Geology, University of Regina, Regina, Saskatchewan, S4S 0A2, Canada |
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| Abstract: | U‐Pb zircon age, geochemical, and Sr‐Nd‐Pb isotopic data of mafic dykes from eastern Shandong Province, eastern China is reported herein. Laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) U‐Pb zircon analyses of two samples from the investigated mafic dykes yield consistent ages ranging from 121.9 Ma ± 0.47 Ma to 122.9 Ma ± 0.61 Ma. The mafic dykes are characterized by high (87Sr/86Sr)i ranging from 0.7087 to 0.7089, low εNd(t) values ranging from ?16.9 to ?17.8, 206Pb/204Pb = 17.15 to 17.17, 207Pb/204Pb = 15.45 to 15.47, and 208Pb/204Pb = 37.59 to 37.68. Results from the current study suggest that the mafic dykes are derived from partial melting of ancient lithospheric mantle that was variably hybridized by melts derived from foundered lower crustal eclogite. The mafic dykes may have been generated through subsequent insignificant crystal fractionation and very minor crustal contamination during magma ascent. Combined with previous studies, the current findings provide new evidence that the intense lithospheric thinning beneath the eastern Shandong Province of eastern China occurred at ～120 Ma, and that this condition was caused by the removal of the lower lithosphere (mantle and lower crust). |
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| Keywords: | Eastern China eastern Shandong Province foundering mafic dykes North China Craton |
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