Abstract The Hengshan–Wutai–Fuping mountain belt constitutes the middle segment of the Trans-North China Orogen, which separates the North China Craton into the Eastern and Western Blocks. The belt consists of the high-grade Hengshan and Fuping complexes, and the intervening low- to medium-grade Wutai Complex. Previous tectonic models assumed that the high-grade complexes were an older basement (Archaean to Palaeoproterozoic) to the low-grade Wutai Complex. However, new geochronological data show that the emplacement of granitoid rocks and eruption of volcanic rocks in the Wutai Complex occurred essentially coeval with or slightly earlier than intrusion of the tonalitic–trondhjemitic–granodioritic (TTG) suites in the Hengshan and Fuping complexes. New isotopic data also reveal the widespread presence of Palaeoproterozoic granitoid rocks in these complexes. Structural and metamorphic data demonstrate similar tectonothermal histories for the three complexes, which are characterized by peak medium- to high-pressure metamorphism accompanied by the development of thrusting, isoclinal folding (F 2 ) and penetrative foliations, followed by near-isothermal decompression and cooling and retrogression associated with the formation of large-scale ductile shear zones and asymmetrical folds (F 3 ) with nearly vertical axial planes. These geochronological, structural and metamorphic data suggest that the tectonic evolution of the Hengshan–Wutai–Fuping mountain belt may not be related to local interaction of the three complexes, as suggested in earlier models, either through closure of a Wutai rift or collision between a Wutai arc and the Hengshan and Fuping micro-continental blocks. Instead, they may represent elements of a single Late Archaean to Early Palaeoproterozoic magmatic arc that was subsequently incorporated into the Trans-North China Orogen along which the Eastern and Western blocks amalgamated to form the North China Craton at around 1.85 Ga.

Abstract SHRIMP U-Pb zircon analyses from eight samples of metamorphosed intermediate to felsic volcanic rocks from the lower, middle and upper ‘subgroups’ of the Wutai sequence in the North China Craton define a weighted mean 207 Pb/ 206 Pb age of 2523 ± 3 Ma. Although individual rock ages range from 2533 ± 8 Ma to 2513 ± 8 Ma, all overlap within the error of the mean and do not support a stratigraphic interpretation for the sequence, since variations within individual previously assigned ‘formations’ in the sequence match the total age range. Contrary to previous interpretations, there is no correlation in age with metamorphic grade. These features highlight the need to reformulate stratigraphic schemes when defining the Precambrian geology of the North China Craton. The similarity in age between volcanic rocks of the Wutai Complex and higher-grade gneisses of the adjacent Fuping and Hengshan complexes supports the view that all three complexes represent portions of a Late Archaean arc complex that was tectonically dismembered and then re-assembled. There is no Fuping or Wutai orogeny in this, its type area: all three complexes were deformed and metamorphosed during collision of the eastern and western blocks of the North China Craton in the Lüliang orogeny c. 1.8 Ga ago.