Late Mesozoic tectonic evolution of the southern Great Xing'an Range, northeastern China: Constraints from detrital zircon U–Pb and Hf isotopes of Late Cretaceous sandstones in the southwestern Songliao Basin

The late Mesozoic magmatism and associated ore deposits were extensively developed in the southern Great Xing'an Range (SGXR), northeastern China. The geodynamic evolution of the SGXR during the late Mesozoic, however, remains controversial. Here, we present new detrital zircon U–Pb and Hf isotopic data of the Late Cretaceous sandstones of the Yaojia and Qingshankou formations from the southwestern Songliao Basin, aiming at constraining their provenance and the late Mesozoic geotectonic evolution of the SGXR. The detrital zircon U–Pb ages of the sandstone samples display similar distribution patterns and mainly fall into two groups (i.e., 267–223 Ma and 169–122 Ma), indicating that they may have a common source area. Furthermore, these zircons have εHf (t) values similar to those of the magmatic rocks in the SGXR and northern North China Block (NCB). Integrated with zircon morphology, zircon U–Pb and Hf isotope indicate that both the SGXR and northern margin of the NCB (limited to the southwest of the Songliao Basin) have provided a dominant provenance for the Yaojia and Qingshankou formations. Similar age distribution patterns and the youngling age trend of the late Mesozoic igneous rocks from the SGXR to the northern margin of the NCB indicate that the Late Jurassic–early Early Cretaceous magmatism in the study area was associated with the evolution of the Mongol–Okhotsk Ocean. In addition, the age distribution patterns, distinct variability of zircon Th/U ratios and development of A‐type granites, volcanic rocks, and metamorphic core complexes demonstrate that the SGXR and northern margin of the NCB have undergone an extensional process since middle Late Jurassic. We therefore propose that the middle Late Jurassic–early Early Cretaceous magmatism in the SGXR and adjacent northern margin of the NCB was associated with an extensional regime induced by collapse or delamination of thickened continental crust corresponding to the closure of the Mongol–Okhotsk Ocean.