Geochronology, sedimentary characteristics and prototype basins of the Yejishan group: Implications for the tectonic framework of the Trans-North China subduction orogenic belt

Li Liyang^1,2Chuanheng Zhang^1*

• ¹China University of Geosciences Beijing, Beijing, China
• ²China Geological Survey Langfang Integrated Natural Resources Survey Center, Tianjin, China

The Yejishan Group is a well-preserved volcano-sedimentary succession in the Lüliang Complex in the central segment of the Trans-North China Orogen (TNCO). The group represents a critical sedimentological archive for investigating the Palaeoproterozoic tectonic evolution of the TNCO. Here, we present new SHRIMP U–Pb ages, sandstone modal analyses, whole-rock geochemical data, and palaeocurrent directions from the Yejishan Group, which constrain the tectonic evolution of the TNCO. The Yejishan Group is divided into the Qingyangshuwan, Bailongshan, and Chengdaogou formations, from base to top, and the succession records a transition from coastal to shallow-marine and ultimately deep-marine environments, forming a transgressive sedimentary sequence. A SHRIMP U–Pb age of 2056 ± 21 Ma obtained from volcanic interbeds in Chengdaogou Formation provides an upper age limit for the Yejishan group. Modal analyses of sandstone indicate that the main provenance of the Yejishan Group was a magmatic arc, and the whole-rock geochemical data further suggest that its provenance was a continental arc. The palaeocurrent data indicate westward sediment transport overall, implying a source to the east. Combining the results with regional geological data, it is concluded that the Yejishan Group was deposited in a back-arc basin during the Palaeoproterozoic and the provenance of the group was a continental arc to the east. Our findings further constrain the tectonic evolution of the North China Craton, supporting its interpretation as a western Pacific–type orogen with westward subduction.