Detrital zircon ages, sources, and implications of the Tangwangling Group, southern margin of the Ordos Block, western North China Craton

The southern margin of the Ordos Block (S-OB) is located in the western part of the southern region of the North China Craton (S-NCC), and has been involved in multiple orogenic episodes that uplifted the North Qinling Orogenic Belt (NQB). Determining whether the S-OB deposits and sources were controlled by late Precambrian or Ordovician tectonic sedimentation is extremely important for understanding the paleo-tectonic evolution of the S-NCC and its relationship with the North Qinling Terrane (NQT). In this study, the depositional age and trace of the source area of the Tangwangling Group (TWL) were constrained using detrital zircon U-Pb isotopic analyses. Six sandstone samples collected from the TWL Group yielded similar detrital zircon age patterns, with four distinct clusters at 2588-2305 Ma, 2100-1600 Ma, 1251-1005 Ma 995-744Ma which correspond to peak ages of 2.45 Ga, 1.80 Ga, 1.10 Ga, and 0.82 Ga, respectively. The youngest zircon ages that peak at 0.82 Ga suggest that the depositional age of the TWL Group is the closest to the late Neoproterozoic, based on comparisons with geochronological data from late Precambrian and Ordovician successions that outcrop in the OB. The detrital zircon age ranges of the TWL Group, in comparison with those of the NCC and NQT, also indicate that clastic grains deposited in the TWL Group were mainly sourced from NCC basement rocks and less so from the late Precambrian NQT complex, which was coincident with a Grenvillian-aged tectonomagmatic event. Thus, we conclude that the NQT had accreted onto the S-NCC before the TWL Group were deposited during the late Neoproterozoic, implying that the S-NCC or the S-OB may have experienced or was at least influenced by the assembly and breakup of Rodinia.