Geochronological constraints of the Huoshan Formation in the Lüliang area: Implication on the Great Unconformity in the central North China Craton

Abstract

The Great Unconformity between the Precambrian basement and the Phanerozoic successions marks a major gap in the stratigraphic records globally. However, previous studies on the time, magnitude, and the spatial distribution of this unconformity in the North China Craton (NCC) mainly focused on the south-eastern margin and were seldom investigated in the central area. In this study, we report detrital zircon geochronological data of the Huoshan Formation, a siliciclastic stratigraphic unit between the Archean-Palaeoproterozoic metamorphic basement and Cambrian successions in the central NCC. The youngest age peak of 685 Ma suggests that the Huoshan Formation was formed in the post-Ediacaran rather than the counterpart of the lower Palaeo-Mesoproterozoic Changcheng Group. The detrital zircons of the quartz sandstone from the Huoshan Formation show varied age populations of 2,700–2,600 Ma, 2,600–2,500 Ma, 2,200–2,000 Ma, 1,900–1,800 Ma, and 700–600 Ma, which correspond to typical tectono-thermal events of the NCC. First, the widely developed Precambrian tectono-thermal events in the NCC were archived in the detrital zircons in the Huoshan Formation, for instance, the crustal growth event at 2,600–2,500 Ma and the 1,850–1,800 Ma magmatic and metamorphic events. Second, the age peaks younger than 1,000 Ma are not distinct in the NCC and are possibly from other terranes. The Great Unconformity represented by the boundary between the Huoshan Formation and the underlying Archean-Palaeoproterozoic basement suggested a high topography and long-term denudation in the Lüliang area during the transition from the Proterozoic to the Phanerozoic.