Detrital zircon U–Pb dating, Hf isotopes and whole-rock geochemistry from the Songshan Group in the Dengfeng Complex: Constraints on the tectonic evolution of the Trans-North China Orogen

Abstract

The Dengfeng, Taihua and Zhongtiao Complexes are located in the southernmost segment of the Trans-North China Orogen, along which the Western and Eastern Blocks amalgamated to form the North China Craton. The Dengfeng Complex consists of the Neoarchean granitoids and supracrustal rocks, of which the latter are subdivided into the Dengfeng and Songshan Groups. The Songshan Group consists of basal conglomerates, quartzites, schists with minor dolomites and phyllites. Geochemistry of the Songshan schists and quartzites are indicative of felsic source rocks and display continental island arc and passive continental margin signatures, respectively. U–Pb ages of detrital zircons from the Songshan Group yielded three age populations of 3700–3100 Ma, 3000–2550 Ma and 2550–1950 Ma. The dominant 3000–2550 Ma detrital zircons were most likely sourced from the TTG gneisses of the Dengfeng and Taihua Complexes. The subordinate 2550–1950 Ma detrital zircons were probably derived from the Paleoproterozoic granitoid plutons and meta-rhyolites in the Dengfeng and Zhongtiao Complexes, and minor amounts of 3700–3100 Ma detrital zircons may have been derived from the Paleoarchean and Mesoarchean crust of the Eastern Block. The youngest detrital zircon age peaks in the Luohandong and Wuzhiling Formations constrain their maximum depositional ages at ∼2350 Ma and ∼1960 Ma, respectively. In combination with the 1775 Ma undeformed granitoids that cut the Songshan Group, the depositional age of the Songshan Group can be constrained in the period between ∼2350 and ∼1780 Ma. Considering the lithostratigraphic feature, provenance and depositional age, the Songshan Group is interpreted as having deposited in a retroarc foreland basin, which is consistent with the model that the collision between the Eastern and Western Blocks to form the Trans-North China Orogen occurred at ∼1.85 Ga after long-lived subduction.