Late Neoarchean multi-stage granitoid rocks in the Dengfeng terrane, North China Craton: Petrogenesis and implications for geodynamic processes

Abstract

During the late Neoarchean era, the rise of K-rich granitoid rocks marked a significant geological event indicative of the maturation and stabilization of continental crust. These granitoids, emerging after tonalite-trondhjemite-granodiorite (TTG) magmatism, stirred debates over the interrelations and geodynamic implications. In this study, diverse granitoid rocks were identified in the Dengfeng terrane of the North China Craton (NCC), dating as approximately 2.63–2.50 Ga. The 2.5 Ga meta-dioritic rocks exhibit elevated MgO (2.2–7.7 wt%) and Mg^# (45–69). Geochemical simulation reveals sanukitoid-like pattern, featuring highly fractionated REE compositions and depleted zircon Hf isotopes (Ɛ_Hf(t) values range from +3.9 to +6.5). Apatite Nd isotopes of ε_Nd(t) values ranging from −0.1 to 4.69. Meta-dioritic rocks were interpreted to be formed by partial melting of a depleted mantle source influenced by subducted slab-derived fluids. The TTG gneiss (2.63–2.52 Ga) exhibit mildly fractionated REE patterns, weakly positive Eu anomalies, lack of magmatic fractionation evidence, and high (La/Yb)_N (6.94–114.9) and Sr/Y (28.6–294) ratios, indicating their formation derived from partial melting of pre-existing low-K mafic crust. The K-rich granitoids (2.56 Ga) are characterized by high K₂O/Na₂O ratios (0.67–1.89), low MgO content and Mg^# (< 1.2 wt% and < 55, respectively). A chain of evidence including geochemical modeling, constant aluminum saturation index (ASI) values of 1.00–1.35, and zircon ε_Hf(t) values ranging from +8.2 to +11.2 suggest their derivation through partial melting of tonalitic rocks. Further analysis suggests that the source for K-rich granitoids are enriched by subducted slab melts or metasedimentary rocks at various crustal depths. In terms of petrogenesis, late Neoarchean granitoid magmatism in Dengfeng terrane likely relates to subduction and accretionary orogeny. Archean active continental margins are vital for early crustal maturation and granitoid diversification during subduction and collision.