Reworking of Eoarchean to Mesoarchean Continental Crust in the Anshan-Benxi Area, North China Craton-Evidence from Lianshanguan ca. 2.5 Ga Syenogranites

The Anshan-Benxi area, situated in the northeast of the North China Craton (NCC), is home to not only the oldest rocks in China (similar to 3.8 Ga) but also a diverse range of granitoids dated between 3.8 and 2.5 Ga. The Lianshanguan batholith, covering an area of approximately 250 km(2) with an east-west trend, predominantly consists of syenogranites (K2O > 4 wt. % and K2O/Na2O ratios > 1.3). Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U-Pb analyses of the two syenogranites yielded concordant ages of 2541 +/- 22 and 2512 +/- 13 Ma, respectively. These syenogranites had zircon epsilon(Hf)(t) values ranging from -20 to +4.9 with two-stage Hf model ages (T-DM2(Hf)) spanning 3.9-2.7 Ga. Based on petrological, geochemical, and isotopic characteristics, we conclude that the Lianshanguan syenogranites are mainly resulted from the reworking of complicated Eoarchean-Mesoarchean crustal materials, possibly with a small proportion of similar to 2.7 Ga juvenile crustal materials. When compared with coeval syenogranites from the Northern Liaoning and Western Liaoning-Eastern Hebei areas, similar to 2.5 Ga syenogranites from the Anshan-Benxi area displayed more complicated T-DM2(Hf) ages, hinting at a pronounced late Neoarchean reworking of the Eoarchean to Mesoarchean continental crust (including metasedimentary sources) primarily in the Anshan-Benxi region of the North China Craton. This scenario significantly bolsters the arc-continent collision model.