Paleozoic Biotite Granites and Rhyolitic Tuffs in Response to Oceanic Subduction in the Dabie Orogen: Constraints From Geochronology and Geochemistry

ABSTRACT Collisional orogens typically record both accretionary and collisional orogenic processes. However, the Dabie orogen in central China lacks accretionary records on the surface due to strong multiple tectonic overprinting and Mesozoic basin cover, hindering understanding of its Paleozoic evolution. We present new geochemical and geochronological results for the Tiechong biotite granites and Maozhuyuan rhyolitic tuffs from the eastern Beihuaiyang zone in the Dabie orogen. Zircon SHRIMP U‐Pb dating indicates that the biotite granites formed at 450 ± 4 Ma, whereas the rhyolitic tuffs formed at 453 ± 3 to 429 ± 2 Ma. The biotite granites show depleted Sr‐Nd‐Hf isotopic compositions, indicating a juvenile crustal source. The rhyolitic tuffs have high SiO 2 content, high A/CNK and variable ε Hf ( t ) values ranging from −7.0 to +10.3, derived from a quartz‐rich psammitic source. The granites and the tuffs both display arc‐like trace‐element signatures, formed at arc and back‐arc settings, respectively. We propose that the roll‐back of the subducted oceanic slab at 450–430 Ma triggered the generation of the granites and the tuffs. These results shed new light on the pre‐collisional history of the Dabie orogen and the Paleozoic convergent process between the North China Block and the South China Block.