Late Ordovician provenance and depositional setting in the southwestern Ordos Block, China: constraints from zircon U-Pb geochronology

다국어 초록 (Multilingual Abstract)

The U-Pb ages of single zircon grains contained in the sandstone samples were analyzed by the LA-ICP-MS method, the sediment provenances and geological significance were discussed. The LA-ICP-MS zircon U-Pb dating from the sandstones, tuffaceous sandstones and volcanic tuffs of the Pingliang and Zhaolaoyu Formations along the southwestern Ordos Block are used to limit the maximum depositional age and material sources. The results show that: (1) The youngest ages of zircon dating in the three samples are 445 Ma, 444 Ma and 443 Ma, respectively, suggesting that the studied Formations were deposited in the Late Ordovician. (2) The detrital zircon U-Pb age analysis of the sandstones sample from the Pinliang Formation clustered in the 445–477 Ma, 588–1548 Ma and 1612–2496 Ma with the corresponding youngest peak age of 454.5 ± 3.3 Ma. (3) The distribution of zircon U-Pb age in sandstone samples showing that the sedimentary rocks detritus was mainly sourced from the North Qinling-Qilian terranes and the NCC, and has double provenance supply in the north and south. The material source of the tuffaceous sandstones and volcanic tuffs mainly comes from the volcanic and magmatic activity related to the North Qilian-North Qinling Island Arcs.