Geochronology and Geochemistry of the Neoarchean Metabasalt in the Southern Liaoning Province, North China Craton: Implications on Regional Crustal Evolution

The development of the continental crust during the Archean era is one of the key issues of geoscience. Determining the geological nature of the Archean terrane of the southern Liaoning Province (SLP) is fundamental to decipher the tectonic framework of the eastern North China Craton (NCC) from the late Neoarchean to Paleoproterozoic. The Archean assemblage of the SLP is composed of metabasalt, deformed diorite, TTG, and granite. Zircon U-Pb and Lu-Hf data constrain that the metabasalt formed at 2.52 Ga and was metamorphosed at 2.49 Ga. Dioritic rocks, TTG (tonalite-trondhjemite-granodiorite) and granite formed between 2.53 and 2.48 Ga. More than 85% of analyzed zircon grains yield εHf(t) values intermediate between coeval CHUR and depleted mantle (DM). Their single-stage (TDM) Hf model ages are dominantly between 2.90 and 2.58 Ga with a peak at 2.76–2.66 Ga, suggesting that the Archean assemblages of the SLP were derived from short-lived crustal sources with limited contributions from older materials. Geochemistry and zircon Lu-Hf systems indicate that these metamafic rocks have N-MORB and island arc-like tholeiitic affinities. Similar basaltic associations were identified from the Wutai greenstone belt. Intra-oceanic subduction and back arc basin extension can be ascribed to the generation of associated MORB-like and arc-related basalt. Along with the closure of the SLP back arc basin, an unknown terrane accreted to the south of the Longgang block at the end of the Neoarchean.