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<p>The Dingqing ophiolite in the eastern segment of the Bangong-Nujiang suture zone records multiple episodes of magmatic events, providing crucial constraints on the tectonic evolution of the Meso-Tethyan Ocean. We focus on sheet dikes recently discovered during the geological survey of 1: 50 000 scale mapping the Dingqing East ophiolite. The studied samples are categorized into two types of high-Ca boninite and high-Mg andesite. Two high-Mg andesite samples yield <i>in-situ</i> zircon U-Pb ages of 161.59 ± 0.59 and 162.85 ± 0.76 Ma, respectively. All samples show high contents of SiO<sub>2</sub> (55.00 wt.%–59.76 wt.%), large range of MgO (4.32 wt.%–17.12 wt.%) and low TiO<sub>2</sub> (0.17 wt.%–0.25 wt.%). In primitive mantle-normalized trace-element diagrams, they are characterized by enrichment in large ion lithophile elements (LILEs) such as Rb and Ba, and depletion in high field strength elements (HFSEs) such as Nb, Ta and Th. The absence of an obvious Zr-Hf spike is distinct from those of Izu-Bonin forearc boninites, but analogues for those of the Tonga boninites. We propose that the boninitic sheeted dikes formed in an ocean-continent subduction zone during the northward subduction of the Meso-Tethyan oceanic slab to the southern Qiangtang continental lithospheric mantle, which was probably influenced by an Early Permian mantle plume.</p>

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Meso-Tethys Ocean-Continent Subduction: Evidence from Zircon U-Pb Age and Geochemistry of Tonga-Like Boninites and High-Mg Andesites in the Dingqing Ophiolite, Xizang

  • 期刊论文

  • 发表日期：

    2026年4月8日

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  • Pengdong Liu,
  • Fei Liu,
  • Xiaohan Gong,
  • Xinyang Zhu,
  • Bo Wu,
  • Guangya Wang,
  • Ahmed E. Masoud

摘要

The Dingqing ophiolite in the eastern segment of the Bangong-Nujiang suture zone records multiple episodes of magmatic events, providing crucial constraints on the tectonic evolution of the Meso-Tethyan Ocean. We focus on sheet dikes recently discovered during the geological survey of 1: 50 000 scale mapping the Dingqing East ophiolite. The studied samples are categorized into two types of high-Ca boninite and high-Mg andesite. Two high-Mg andesite samples yield in-situ zircon U-Pb ages of 161.59 ± 0.59 and 162.85 ± 0.76 Ma, respectively. All samples show high contents of SiO2 (55.00 wt.%–59.76 wt.%), large range of MgO (4.32 wt.%–17.12 wt.%) and low TiO2 (0.17 wt.%–0.25 wt.%). In primitive mantle-normalized trace-element diagrams, they are characterized by enrichment in large ion lithophile elements (LILEs) such as Rb and Ba, and depletion in high field strength elements (HFSEs) such as Nb, Ta and Th. The absence of an obvious Zr-Hf spike is distinct from those of Izu-Bonin forearc boninites, but analogues for those of the Tonga boninites. We propose that the boninitic sheeted dikes formed in an ocean-continent subduction zone during the northward subduction of the Meso-Tethyan oceanic slab to the southern Qiangtang continental lithospheric mantle, which was probably influenced by an Early Permian mantle plume.