Paleozoic magmatic rocks and metamorphism in the Dabie orogen, central China

The Qinling-Tongbai-Hong’an-Dabie orogenic belt records complex tectonic evolution history from the Paleozoic to the Mesozoic. However, the Paleozoic magmatism and metamorphism of the Dabie orogen remain poorly constrained. This study presents an integrated geochemical, geochronological, and isotopic investigation of mylonitized monzonite and granite in the Beihuaiyang zone. Zircon U-Pb dating and Hf isotopic analysis reveal that the granite from the Tiechong pluton formed at ca. 451 Ma with positive εHf(t) values (10.3−14.4), whereas the monzonite from the Gongdian outcrop crystallized at 481 ± 4 Ma with negative εHf(t) values (−7.2 to −0.7). Geochemical signature and zircon Hf isotopic composition of monzonite provided clear evidence for its genesis in a continental arc setting with significant crustal materials. Metamorphic zircon and titanite U-Pb ages documented multiple Carboniferous−Permian tectonic-thermal metamorphism at ca. 340 Ma, 313 Ma, and 283 Ma. The high-temperature metamorphism in the eastern Dabie orogen shows a clear contrast to the high-pressure/low-temperature metamorphism in the Hong’an orogen, indicating tectonic variations within the oceanic subduction system. These new data provide critical petrological and geochemical evidence for the eastward extension of the Paleozoic Qinling orogen and the Shangdan Ocean into the Dabie orogen, offering new constraints on the lateral tectonic correlation and evolution history of the Qinling−Tongbai-Hong’an-Dabie orogenic belt.