Featured Neoarchean granitoid association in the central North China Craton: An indicator of warm plate subduction

Diverse Neoarchean granitoid assemblages, which generally include tonalites−trondhjemites−granodiorites (TTGs) and various K-rich granitoids, are prevalent in most basement terranes of the North China Craton. However, the Hengshan terrane is an exceptional case in the North China Craton; it is dominated by late Neoarchean sodic diorite-TTGs (DTTGs) and sanukitoids. These sanukitoids are the only high-K granitoids and show Mg-rich chemical features. The late Neoarchean DTTGs and sanukitoids were generated at ca. 2486−2537 Ma and show an intimate spatial association. The granitoid assemblages of the DTTGs and sanukitoids are characterized by high Mg# [100 × Mg/(Mg + Fetotal)] values (43−65) and enriched in light rare earth elements, large ion lithophile elements, heterogeneous zircon Lu−Hf (εHf = −1.6 to +7.4), and whole-rock Sm−Nd (εNd = +0.9 to +4.2) isotopic components, which indicates that they may be derived from varying degrees of interactions between mantle peridotite and subduction-related materials. Combined with the relatively high apparent geothermal gradient (∼17 ± 2 °C/km) and the relatively low basal heat flow of continental crust (∼25 ± 5 mW m−2), the crust-mantle interaction process indicates that the occurrence of late Neoarchean high-Mg magmatism was closely related to warm oceanic slab subduction in the Hengshan terrane, and the featured lithological association of DTTGs and sanukitoids most likely developed in the active continental margin at the end of the Archean.