A Buried Columbia‐Forming Orogen Front Located in the Northwestern North China Craton

Abstract The Inner Mongolia Suture Zone (IMSZ) in the North China Craton is an important component of the Colombia‐forming orogen, and its southern may have preserved the deformation relics of the ancient orogen front due to being prolonged buried beneath the Ordos Basin. Here we used the high‐resolution seismic profiles in the North Ordos Basin and U‐Pb zircon age data from the borehole basement samples to discover the existence of wedge tectonics consisting of thrust belt and ramp structure within the basement and to fingerprint markedly different basement ages on both sides of the Thrust Front Belt (TFB). The footwall rocks (∼2.2–1.95 Ga) have a dominant affinity with the south‐central Ordos Block (OB), while the hanging wall rocks (∼2.51–2.46 Ga) have no immediate affinity with the OB, possibly representing a set of late Neoarchean‐early Paleoproterozoic island arc formations developed in the northern margin of the OB (termed the Hangjinqi Terrane). So our preferred interpretation posits that the wedge tectonics was formed by wedging the OB into the underthrusting Hangjinqi Terrane during the ∼1.95 Ga collision between the Yinshan Block and OB, with the TFB demarcated as the tectonic boundary separating the OB and IMSZ. This wedge tectonics in the late Paleoproterozoic orogen flank bears a striking resemblance to crustal structures in Phanerozoic orogenic settings, suggesting that this orogenesis mode of crustal deformation has been initiated at least in the Orosirian and may have been a significant orogen mode for the assembly of the Columbia supercontinent.