Stratigraphy and Zircon Provenance of a Late Paleoproterozoic Terrestrial Sequence underlying the Xiong'er Volcanics in the Southern North China Craton

Abstract

AbstractThe late Paleoproterozoic Dagushi Formation comprises a fluvial‐lacustrine succession and represents the initial fill of the Xiong'er Basin in the southern North China Craton. Employing integrated outcrop surveys and detrital zircon U‐Pb‐Hf dating, this study examines the provenance and depositional setting of the Dagushi Formation. Five major depositional facies, including braided channel, distributary channel, subaqueous stream/mouth bar, pro‐delta and shallow lake, were identified, based on lithofacies and associations. They were interpreted as representing a braided river delta‐lacustrine system. The ages of the last metamorphic event of the basement, covering volcanics and the youngest zircon together constrain a depositional age of ca. 1.79 Ga for the Dagushi Formation. Zircon age distributions reveal a provenance change from ca. 2.7–2.5 Ga rocks in the lower part, to ca. 2.3–1.9 Ga sources in the middle‐upper part of the Dagushi Formation. Considering the vertical sedimentology, this provenance change could be induced by the rising water‐level caused by a tectonic subsidence. The ca. 2.7–2.5 Ga zircons are suggested to be locally sourced from the late Neoarchean–Paleoproterozoic metamorphic basement. The northeast Zhongtiao Mts area (current co‐ordinates) is supposed to have appeared as a paleo‐uplift and served as a source area for the Paleoproterozoic grains. The Dagushi Formation records an early ‘underfilled’ stage of the Xiong'er Rift.