Late Triassic extensional tectonics in the northern North China Craton, insights from a multidisciplinary study of the Wangtufang pluton

Huabiao Qiu (1, 2, 3) , Wei Lin (1) , Michel Faure (2, 3) , Yan Chen (2, 3) , Lingtong Meng (1) , Jipei Zeng (1) , Zhiheng Ren (1) , Yin Wang (1) , Qiuli Li (1)

1 SKL - State Key Laboratory of Lithospheric Evolution
2 Géodynamique - UMR7327
3 ISTO - Institut des Sciences de la Terre d'Orléans - UMR7327

To better understand Late Triassic tectonic setting in the northern North China Craton (NCC), the emplacement mechanism of the Wangtufang pluton, which recorded the synmagmatic regional tectonic signature, has been investigated. Zircon U-Pb ages, and Hf isotopic data, and whole-rock geochemical analyses suggest that the Late Triassic Wangtufang pluton composed of syenogranite and diorite is derived from partial melting of lower crust with some depleted mantle components. Both the syenogranite and diorite appear isotropic. Anisotropy of magnetic susceptibility and gravity studies have been carried out to characterize internal fabrics and shape of the pluton. The diorite forms just thin remnants above the syenogranite. The syenogranite with a series of NW-SE trending dykes intruded into the diorite and its country rocks. In the syenogranite, the gently dipping magnetic foliations strike nearly parallel to the pluton border. The shallow plunging magnetic lineations mainly strike NE–SW. Combining NE-SW trending elongated subsurface shape with central root, unflat bottom, and moderate- to high- inward dipping sidewalls, the syenogranite could be considered as a lopolith-like intrusion. The syenogranite was likely emplaced by inflation of magma pulses from its central conduit and built up by floor depression. Emplacement of the syenogranite was in an extensional setting, considering: (1) the NE–SW striking magnetic lineation, (2) the NE–SW trending elongated subsurface pluton shape, and (3) the orthogonal NW–SE striking syenogranitic dykes considered as tension gashes during the NE–SW trending extension. The Wangtufang pluton provides reliable arguments to the Late Triassic intracontinental extensional setting already suggested in the northern NCC.

Mots clés: early Mesozoic magmatism; North China Craton; Wangtufang pluton multidisciplinary study; Late Triassic extensional tectonics

Domaines: Tectonique

Huabiao Qiu, Wei Lin, Michel Faure, Yan Chen, Lingtong Meng, et al.. Late Triassic extensional tectonics in the northern North China Craton, insights from a multidisciplinary study of the Wangtufang pluton. Journal of Asian Earth Sciences, 2020, 200, pp.104462. ⟨10.1016/j.jseaes.2020.104462⟩. ⟨insu-02877251⟩