Within-plate granitoids in the Jiaobei Terrane were products of a possible tectonic switch from rifting to subduction collision at ca. 2.1 Ga in the North China Craton

Abstract The long-standing debate over whether the 2.2–2.1 Ga magmatism in the North China Craton was characterized by the opening and closing of continental rifts or subduction-collision processes has yet to reach a consensus. In this contribution, we present an integrated petrological and geochemical study on the 2.13–2.08 Ga Dongbaishishan syenites and monzo-syenogranites and Gujiacun monzogranites in the Jiaobei Terrane of the North China Craton. These granitoids display high SiO2, Na2O + K2O, Zr, Nb, Ga, Y, and heavy rare earth element contents, low MgO, Sr, P, Nb, Ta, and Ti concentrations, and negative Eu anomalies (0.25–0.86), together with high zircon saturation temperatures of 817–891 °C (an average of 851 °C), strongly suggesting A-type geochemical affinities. The rocks exhibit evolved Hf isotopic compositions (εHf[t] = −10.61 to +6.52, depleted mantle model ages with reference to the average continental crust [TDMC] = 2.9–2.5 Ga), supporting their derivation from remelting of 2.9–2.5 Ga Archean tonalite-trondhjemite-granodiorite under high heat flow and shallow depths, with minor contributions from juvenile mantle–derived materials. Likewise, the Gujiacun monzogranites and Dongbaishishan monzo-syenogranites and syenites show increasing δ18O values of 5.48‰–12.22‰, especially the Dongbaishishan granitoids, which show more enriched 18O (most δ18O values >8‰, up to 12.22‰), high Al2O3 contents and K2O/Na2O ratios, and low Fe2O3T contents, indicating the incorporation of sedimentary materials into their sources. The three granitoids have high Zr, Y, Nb, Rb, and Ta concentrations and plot mainly in the within-plate field, implying a continental rifting system operated in the North China Craton during 2.2–2.1 Ga. Further, a systematic compilation of published age and geochemistry data of 2.2–2.0 Ga granitoids in the North China Craton was conducted to provide key constraints on the early Paleoproterozoic tectonic setting. All the recompiled granitic rocks can be divided into two groups: group 1 (G1, 2.19–2.08 Ga) and group 2 (G2, 2.10–2.05 Ga). Most of the G1 granitoids exhibit rift-related A-type affinities. Combined with coeval tholeiitic mafic rocks and associated bimodal volcanic-sedimentary sequences, the extensional rifting system interpretation is highly reliable for the North China Craton ca. 2.2–2.1 Ga. In contrast, most of the G2 granitoids show attributes of arc-like I-S–type granites. Associated with synchronous calc-alkaline mafic magmatism, we suggest they were the products of subsequent subduction-collision in the North China Craton at ca. 2.1–1.8 Ga, supporting a consensus that the orogenic event was part of a global network of subduction zones and collisional belts facilitating the assembly of the supercontinent Columbia. This unusual temporal and compositional transition from G1 to G2 magmatism in the North China Craton may hint at a marked tectonic transition from extension to compression environments between 2.2 Ga and 2.0 Ga, potentially linked to global-scale supercontinent aggregation events.