The Early Permian Woniusi Flood Basalts from the Baoshan Terrane, SW China: Petrogenesis and Geodynamic Implications
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We are grateful to two reviewers for their very useful and detailed constructive journal reviews that helped improve our arguments. Thanks are given to Liu Ying, Hu Guangqian, Tu Xianglin and Bai Xiujuan for laboratory assistance. This research was supported by the National Natural Science Foundation of China (NSFC) (No. 41703030), Natural Science Foundation of Jiangxi Province (No. 20192BAB213024), China Scholarship Council (No. 201808360273), and the research grant of Shandong Key Laboratory of Depositional Mineralization & Sedimentary Minerals, Shandong University of Science and Technology (No. DMSM20190029).

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    Abstract:

    The Woniusi flood basalts from the Baoshan terrane, SW China, represent a signi?cant eruption of volcanic rocks which were linked to the Late Paleozoic rifting of the Cimmeria from the northern margin of East Gondwana. However, the precise mechanism for the formation and propagation of the rifting is still in debate. Here we report 40Ar/39Ar dating, whole-rock geochemistry, and Sr–Nd–Pb isotopes for the Woniusi basalts from the Baoshan terrane of SW China, with the aim of assessing if a mantle plume was related to the formation of the continent Cimmeria. 40Ar/39Ar dating of the Woniusi basalts yielded ages of 279.3 ± 1.1 Ma and 273.9 ± 1.5 Ma, indicating they were emplaced during the Early Permian. Whole-rock geochemistry shows that these basalts have subalkaline tholeiitic af?nity, low TiO2 (1.2–2.2 wt%), and fractionated chondrite-normalized LREE and nearly ?at HREE patterns [(La/Yb)N = 2.86–5.77; (Dy/Yb)N = 1.21–1.49] with noticeable negative Nb and Ta anomalies on the primitive mantle-normalized trace element diagram. The ?Nd(t) values (?4.76 to +0.92) and high (206Pb/204Pb)i (18.40?18.66) along with partial melt modeling indicates that the basalts were likely derived from a sub-continental lithospheric mantle (SCLM) source metasomatized by subduction-related processes. On the basis of a similar emplacement age to the Panjal basalts and Qiangtang mafic dykes and flood basalts in the Himalayas, combined with a tectonic reconstruction of Gondwana in the Early Permian, we propose that the large-scale eruption of these basalts and dykes was related to an Early Permian mantle plume that possibly initiated the rifting on the northern margin of East Gondwana.

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CAO Jun, ZHANG Gaizhi, WANG Xuan, CHEN Jun.2020. The Early Permian Woniusi Flood Basalts from the Baoshan Terrane, SW China: Petrogenesis and Geodynamic Implications[J]. Acta Geologica Sinica(),94(6):2091-2114

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History
  • Received:May 12,2019
  • Revised:December 02,2019
  • Adopted:
  • Online: December 25,2020
  • Published: