U–Pb age and Hf isotopic data of detrital zircons from the Devonian and Carboniferous sandstones in Yimin area, NE China: New evidences to the collision timing between the Xing’an and Erguna blocks in eastern segment of Central Asian Orogenic Belt

Abstract

New U–Pb age data and Hf isotope systematics on zircons from Middle Devonian and Lower Carboniferous units from NE China provide evidence for the depositional age of these poorly constrained units as well as for the timing of the collision between the Erguna (Ergun in some references) and Xing’an blocks in the eastern end of Central Asian Orogenic Belt (CAOB). The detrital zircons from the Devonian and Carboniferous sandstones yielded similar age spectra in probability diagrams showing three distinct peaks at ∼450Ma, ∼500Ma and ∼540Ma, respectively, along with Proterozoic and Archean age groups, except for a relatively young age population at ∼360Ma detected for zircons from the Hongshuiquan Fm.The dating results suggest that the depositional time of the Niqiuhe Fm. should be younger than Late Silurian, as indicated by the youngest 422-Ma detrital zircon from this Fm., and that of the Hongshuiguan Fm. with a youngest detrital age of ca. 338Ma, is younger than Middle Mississippian (Visean), which is in accordance with those inferred from biostratigraphic data.These dominant age groups are widely found in the Erguna and Xing’an blocks, it is suggested that the sediments of the studied sandstones from Niuqiuhe and Hongshuiquan Fms come mainly from the Erguna and Xing’an blocks. The εHf (t) value of dated zircons from our sandstones has a wide range (−21 to 16), which shows a mixed signature of that from Paleozoic granitoids in Xing’an block (6–17) and Erguna block (−2 to 6), indicating that Erguna and Xing’an blocks had connected before the Middle Devonian deposition of the Niqiuhe Fm. (422±5Ma). Combined with the age data, we suggest that the Erguna and Xing’an blocks started to accrete at ∼540Ma, reached the peak of collision at ∼500Ma, and went into the post-collision stage from ∼490 to ∼450Ma. The study provides more evidences and constraints for the early Paleozoic evolutions of the inter-continental block amalgamations and accretions in CAOB.