Characteristics Of Geochronology, Geochemistry Of Late Paleozoic And Mesozoic In Weihe Region And Its Tectonic-Sedimentary Significance

Based on the distribution of residual strata in the Weihe and its adjacent region, the Permian and Triassic to the north and south Weihe region were compared by the methods of petrology, U-Pb isotopic chronology and major-trace elements, and we reconstructed original sedimentary facies from the Late Paleozoic-Early Mesozoic in study area. Furthermore, the Late Mesozoic reformation process was discussed according to simulation of fission track (FT). The study showed that the main sedimentary centers in the Weihe basin might remain small-scale and discontinuous Cretaceous-Permian (C-P) strata without Mesozoic strata. The results of petrology, U-Pb ages of zircons and major-trace elements suggested that the Permian and Triassic in the southern Ordos and northern Qinling regions were well contrasted, both of which are the same basin. The provenance of Permian was characterized with the recycled orogenic zone and continental sources, which are mainly derived from metamorphic elastic rocks in the Kuanping Group and volcanic-sedimentary rocks in the Erlangping Group. The provenance of Triassic might derive from the Kuanping Group, Qinling Group or contemporaneous volcanic rocks. The results of fission track dating revealed that the Mesozoic uplift of Weihe region, Weibei uplift as well as northern Qinling area had consistent evolution stages. Late Jurassic-Early Cretaceous, the geological evolution was dominated by tectonic deformation and weak uplift. Since the Early Cretaceous, the strata had been extensively uplifted and eroded, which led to less residual strata of the Upper Paleozoic-Mesozoic in the Weihe region. This research suggested that the evolution phases from Late Paleozoic-Mesozoic can be divided into Permian, Triassic-Early Jurassic, Late Jurassic-Early Cretaceous, and Late Cretaceous.