In situ titanite ages and Mesozoic metamorphism of Paleoproterozoic mafic granulites from the Wuhe metamorphic complex, southeastern North China Craton

Abstract

The Wuhe Complex in the southern section of the Jiao-Liao mobile belt (JLMB) consists of an Archean–Paleoproterozoic crystalline basement and is essential for understanding the intricate tectonic evolution history of the southeastern North China Craton (NCC). Owing to the lack of Mesozoic metamorphic ages reported from the southern section of the JLMB, it is unclear whether the Wuhe Complex experienced Mesozoic tectonothermal overprint events. Titanites are common uranium-bearing minerals for U–Pb dating and are prone to metamorphic, tectonothermal, or hydrothermal processes. Thus, titanites were used in this study to unravel late metamorphic overprint events. Mesozoic titanites from the mafic granulites of the Wuhe Complex are believed to be of metamorphic origin and have experienced amphibolite-facies metamorphism, with a temperature range T = 677–723 ℃ and a pressure of P = 3.8 kbar. Laser ablation-inductively coupled plasma-mass spectroscopy U–Pb dating and in situ U–Pb dating of titanites yielded ages of 163–112 Ma and 123 Ma, respectively. This implies that the Wuhe Complex may have experienced a Mesozoic metamorphic overprint event during the tectonic transition period (from a subduction-related compressive setting to a tectonic stretch setting). Given the large number of Mesozoic intrusive rocks distributed across the NCC, it is important to rule out the effect of late tectonothermal events when studying Neoarchean or Paleoproterozoic metamorphism in the NCC.