Detrital Zircon Trace Elements, U-Pb Geochronology and Its Geological Significance of the “Huoshan Sandstone” in Xiweikou Area of the Eastern Margin of Ordos Basin

Determining the age and origin of the “Huoshan Sandstone” holds significant geological implications for the stratigraphic division and correlation of Precambrian sequences in the North China Craton, provenance analysis, reconstruction of tectonic–sedimentary patterns, and paleogeographic settings restoration. This paper investigates the petrology, zircon U-Pb dating, Hf isotopes analysis, and zircon microzonation geochemistry of the “Huoshan Sandstone”. The “Huoshan Sandstone” is grayish-white, light gray, light yellow, purplish-red quartzitic sandstone and quartz sandstone, with a quartz content ranging from 85.5% to 97.8%. The quartz grains exhibit relatively straight contact edges, characteristic of low-grade metamorphosed quartzite. The protolith of the “Huoshan Sandstone” is a medium-grained quartz sandstone with dominant grain sizes of 0.30~0.50 mm, exhibiting well-rounded to subrounded grains and highly developed siliceous cementation characterized by secondary overgrowth. The zircon Th/U ratio confirms that the zircons in the “Huoshan Sandston” are mainly magmatic zircons. Most zircons exhibit extreme HREE enrichment and left-sloping REE patterns, and show significant positive Ce anomalies (Ce/Ce* of 1.06~290.68) and negative Eu anomalies (Eu/Eu* of 0.065~0.61). The age range of zircon 207Pb/206Pb is 1770 ± 20~2732 ± 16 Ma, and there are two obvious peaks at 1800 and 2500 Ma in the U-Pb age frequency histogram, the age of the intersection point on the concordia line is 2521 ± 31 Ma, and the age of the intersection point on the lower part of the line is 1829 ± 22 Ma. These two ages correspond to the timing of Neoarchean TTG gneiss formation through oceanic crust partial melting in the central North China Craton, and the ~1.85 Ga Paleoproterozoic thermal metamorphic event recorded in the Zhongtiao Group of the same region, respectively. The maximum depositional age of the “Huoshan Sandstone”, constrained by the youngest detrital zircon U-Pb ages at 1770 ± 20 Ma, indicates that its sedimentation occurred after 1770 ± 20 Ma (Late Late Paleoproterozoic). Furthermore, as it underlies the red shales of the Cambrian Mantou Formation as a distinct tectonic layer, it must have formed prior to the deposition of the Cambrian Mantou Formation. In addition, in situ Lu-Hf isotopic analyses of these zircons yielded two-stage model ages, mainly between 2.5 and 2.8 Ga, suggesting the provenance to be the Precambrian basement of the Zhongtiao Mountain region in the central North China Craton. It is inferred that the Precambrian strata in the Zhongtiao Mountain area were involved in the process of subduction, collage, and collision of the two continental blocks of the eastern and western parts of the North China Craton, and further confirmation is provided that the final collision of the two continental blocks to form the central orogenic belt occurred in the late Palaeoproterozoic.