Detrital Zircon U-Pb-Hf Isotopes of the Changzhougou Formation in the Central–Southern Taihang Mountains and Their Tectonic Implications

Abstract

The Changchengian System represents one of the earliest sedimentary covers deposited on the Archean–Paleoproterozoic basement of the North China Craton. We report zircon U-Pb-Hf isotope data for Changzhougou Formation sandstones in the Chaiguan area, central–southern Taihang Mountains. The youngest detrital zircon ages (∼1782 Ma) constrain the maximum depositional age to ∼1.78 Ga. Combined with regional constraints, deposition is bracketed between ∼1.76 and ∼1.64 Ga. Detrital zircon age spectra exhibit a dominant peak at ∼2.5 Ga, with secondary peaks at 2.8–2.6, 2.2–2.0 and 1.9–1.8 Ga, alongside rare ∼3.25 and ∼3.70 Ga grains. Coupled with Hf isotopic signatures, these diverse populations suggest derivation primarily from the basement of the Trans-North China Orogen. Although the age spectra are broadly similar to the Archean-dominated Yanliao Rift, the presence of subordinate Paleoproterozoic and minor Paleoarchean grains, coupled with a predominant southeast-to-northwest paleocurrent, implies a closer affinity with the Xiong'er Group. These results suggest deposition in an extensional setting—likely associated with the breakup of the Columbia supercontinent—and record a northward marine transgression from the Xiong'er Rift Basin. Consequently, the central–southern Taihang Mountains served as a critical transition zone connecting the Xiong'er Basin with the Yanliao Basin.