ABSTRACT The North China Craton (NCC), situated in the southeast of the Central Asian Orogenic Belt, offers an excellent opportunity to explore the subduction-accretion process of the Paleo–Asian Ocean Plate. Tectonic and magmatic evidence indicates that during the Late Carboniferous to early Permian, the northern margin of the NCC was an Andean-type active continental margin, with the Inner Mongolia Paleo-Uplift serving as a magmatic arc. However, the Carboniferous deposits in the forearc region are characterized by shelf–fluvial sediments, traditionally interpreted as indicative of a passive-margin or post-collisional settings. To resolve this apparent discrepancy, we conducted facies and provenance analysis of the Carboniferous deposits in the Aohanqi region to reconstruct the paleogeography and explore the nature of the basin along the northern margin of the NCC. The Carboniferous deposits formed in the offshore, delta, and braided-river environments. The sedimentary facies constitutes a progradational succession, transitioning from the delta-front to braided-river associations along the basin edge, and from the offshore to delta-front associations in the basin interior. Provenance results indicate that the sediments originated from the Inner Mongolia Paleo-Uplift, with sandstone consisting of volcanic lithics (17–75%), quartz (13–68%), and feldspar (6–38%). The detrital zircons yield U–Pb ages of 1.85 and 0.33 Ga, aligning with the Precambrian crystalline basement and intrusive rocks present in the Inner Mongolia Paleo-Uplift, respectively. Geochemical data further corroborate the mixed origin of these rocks. The upward increase in content of quartz and Precambrian zircon, coupled with progradation in basin filling, suggests that the Inner Mongolia Paleo-Uplift underwent tectonic uplift and exhumation during the Carboniferous. Considering the arc magmatic activity in the Inner Mongolia Paleo-Uplift, we propose that the Aohanqi basin represents a shelved forearc basin. This study emphasizes the potential to identify atypical forearc basins by coupling progradational succession and exhumation of active magmatic arcs in ancient orogens.
Ma et al. (Wed,) studied this question.