Archean Geodynamic Regimes of the Southeastern North China Craton: Insights from Petrological and Geochemical Constraints

The nature and origin of Archean tectonic features that appear analogous to modern-style subduction remain insufficiently constrained. In this study, we investigated a variety of rock specimens from the southeastern margin of the North China Craton (SENCC). Samples obtained from Archean outcrops in the Luxi area and drill cores from the Xincai area were integrated with previously published data. Samples collected here were analyzed for whole-rock major and trace elements and zircon-based U-Pb and Lu-Hf isotopes. The sample was divided into four groups: (i) tonalite-trondhjemite-granodiorite (TTGs) trend rocks (TTGs, meta-luminous granitoids, and granites); (ii) Calc-alkaline trend rocks (sanukitoids, monzogranites, potassic granites, and calc-alkaline basalts); (iii) tholeiitic basalts; and (iv) alkali basalts . The ~2.90 and 2.70 Ga in Huoqiu-Wuhe TTGs share the same model ages (TDM = 3.0–3.25 Ga), while the ~2.70 Ga calc-alkaline rocks fall into arc-related field on tectonic discrimination diagrams, suggesting the occurrence of a crust material recycling process at that time. However, the positive Ti anomalies, which are typically associated with partial melting events occurring in the stability fields of rutile and garnet, are lacking in these ~2.70 Ga samples, indicating that the recycling process is shallower compared to modern subduction zones. We propose that this subduction may be driven by a micro-block rather than a relatively larger continental crust, suggesting that horizontal accretion had emerged by at least ~2.70 Ga. Following this, multiple micro-blocks assembled, leading to the formation of the Xuhuai micro-block at ~2.50 Ga, as indicated by widespread calc-alkaline magmatic activities. This revisionist perspective provides a novel framework for understanding tectonic regime transitions in Archean SENCC.