Provenance and Tectonic Evolution of the Kongtongshan Formation Conglomerate in Southwest Ordos Basin, China.

The Kongtongshan Formation (KTSF) conglomerate in the southwestern Ordos Basin is located at the intersection of China's North-South Tectonic Belt (NSTB) and the East-West Central China Orogenic Belt (CCOB), which are crucial for reconstructing the Early Mesozoic prototype basin and understanding the regional tectonic evolution of the North China Craton (NCC). However, the depositional age and material sources of the KTSF conglomerate remain controversial. In this study, we conducted zircon LA-ICP-MS U-Pb dating and trace element analysis on sandstones, combined with paleocurrent direction measurements and field outcrop surveys, to constrain the sedimentary age and provenance of the KTSF conglomerates and reconstruct the regional tectonic evolution. The results show that the youngest detrital zircon age of the KTSF is 223 ± 2 Ma, indicating the maximum age of sediment deposition in the Late Triassic. The detrital zircon U-Pb ages of the samples fall into four distinct populations, and most of them exhibit double peaks, which are 269.0 Ma and 445.3 Ma, 933.9 Ma and 982.2 Ma, 1600.5 Ma and 1880.8 Ma, 2498.3 Ma, and >2876.2 Ma, respectively. Based on the predominantly southwest and minor northwest paleocurrent directions, the provenance of the KTSF is primarily derived from the North Qilian Orogenic Belt (N-QLOB) and the southern part of the North China Plate (SNCP), with minor contributions from the North Qinling Orogenic Belt (NQOB) and the Alxa Block (AB). The study reveals significant differences in the Triassic collision and orogenic processes between the N-QLOB and NQOB with the NCC. While the NQOB experienced strong intrusion and subduction, the N-QLOB was primarily characterized by strike-slip compression and collision.