Geochemistry Characteristics and Detrital Zircon In–Site U–Pb Geochronology of Silurian Diebu Formation in Bailongjiang Area, West Qinling Mountains

Trace element geochemistry of the shallow metamorphic clastic rocks of the Silurian Diebu Formation in the Bailongjiang area indicates that their provenance is mainly derived from felsic magmatic rocks in the upper crust, and the source area is closely related to the background of the active continental margin. LA–ICP–MS detrital zircon U–Pb chronology of the Diebu Formation shows a large age span, with a minimum age of 440 Ma, indicating that its sedimentary age is not earlier than the Early Silurian. Combined with regional fossil data, the Diebu Formation is defined as the Early Silurian. The U–Pb ages of detrital zircons can be divided into five peak age ranges of 440～680 Ma, 798～876 Ma, 1012～1291 Ma, 1590～1 990 Ma, and 2113～2455 Ma, indicating that the sediment sources in the area have the contribution characteristics of multiple sources and multiple ages of geological bodies. The age spectrum with the highest peak value of 440～680 Ma (accounting for 76.9% of the total effective data) is highly consistent with the north Qinling microblock, indicating that the sediment sources of the Diebu Formation mainly come from the north Qinling microblock, while a small amount of peak clastic zircon ages of other groups indicate that the south Qinling microblock, the Yangtze block, the eastern section of the north Qilian mountains may participate in some source supply.