A tentative discussion on the source area of the Late Triassic Liuyehe basin in North Qinling Mountains and its relationship with the Ordos basin: Evidence from LA-ICP-MS U-Pb dating of detrital zircons

In this paper, the authors collected quartz sandstone samples from late Triassic Liuyehe basin of North Qinling Mountains in Zhouzhi area, Shaanxi Province, and conducted LA-ICP-MS detrital zircon U-Pb isotope analysis. The results show that the 77 analytical points of the magmatic detrital zircons yielded seven age groups: 256~475Ma, 1500~1680Ma, 1750~2190Ma, 2190~2310Ma, 2400~2650Ma, 2700~2800Ma, and 2850~2960Ma. Among the ages, the youngest age is 256±4Ma, whereas the oldest age is 2954±25Ma; the major Paleoproterozoic age group (1750~2190Ma) accounts for 64% of the total measured points. The zircon age comparison between the Carboniferous Liuyehe basin and the late Triassic Liuyehe basin shows that the Neoproterzoic age is lacking in the Late Triassic Liuyehe basin, which indicates that the uplifting northern part in EW-trending North Qinling Mountains located between Liuyehe basin and Ordos basin during the Carboniferous was removed in Late Triassic and became the secondary provenance of Liuyehe basin. A comparative study of the age structure of the peripheral terranes shows that the southern part of North Qinling Mountains, including the Erlangping, Qinling, Danfeng and Liuling groups as well as the magmatic material developed in the Caledonian trench-arc-basin system along the Shangdan suture zone, became the major provenance for the basin. Combined with the paleontologic evidence, the similarity in detrital zircon age distribution pattern between the Triassic Liuyehe basin and the Yanchang formation in southwest Ordos basin strongly suggests that the Liuyehe basin was probably connected with the southern Ordos basin and represented the southern margin of the Ordos basin during the Late Triassic.