Petrogenesis of the Paleoproterozoic Wulong Gabbros: Insights into the post-collisional evolution of the southern North China Craton

• The Wulong gabbros mark the initiation of post-collisional extension of the NCC. • The Wulong gabbros were formed from 3–5 % partial melting of an enriched spinel-bearing lithospheric mantle. • The mantle source of the Wulong gabbro was metasomatized by subduction-related fluids (0.5–10 %). • The primary melts exhibit moderate mantle potential temperatures (∼1361 °C) and pressures (∼1.83 GPa or ∼60 km). • The Wulong primary melts are stored and differentiated in a thickened crust. The North China Craton (NCC) has preserved nearly 3.8 billion years (Ga) of Earth’s evolutionary history. Although the formation and amalgamation mechanism of the NCC remains debated, it is widely accepted that its final collisional assembly was completed at ∼1.85 Ga, followed by over a billion years of stability. However, the timing of the post-collisional extension is not well constrained, leaving uncertainties in the mantle and crustal evolution processes after the craton’s formation. Here, we present new detailed geochronological, petrological, and geochemical data of Paleoproterozoic Wulong gabbros to investigate their origin and tectonic implications for the evolution of the NCC. Zircon and titanite U–Pb isotopic dating indicate that the Wulong gabbros formed at 1830 ± 19 Ma. The Wulong gabbros have low SiO 2 (49.4–52 wt%) and variable contents of MgO (3.9–7.2 wt%) with sub-chondritic Nd isotope compositions (εNd (t) from −7.34 to −3.26), suggesting it was derived from the enriched mantle source. Reverse crystallization calculations indicate that the primary melts exhibit low SiO 2 (∼48.1 wt%) and high MgO (∼16.3 wt%) contents, along with moderate mantle potential temperatures (∼1361 °C) and pressures (∼1.83 GPa or ∼60 km). The new results suggested that the source magmas formed through 3–5 % partial melting of a spinel-bearing lithospheric mantle previously metasomatized by 0.5–10 % subduction-related fluids. The generated parental basaltic melt underwent fractional crystallization and minor plagioclase accumulation at approximately 1 GPa. Our new findings highlight that the Wulong gabbros were sourced from the extensional lithospheric mantle but stored in the thickened crust, marking the onset of post-collision extension in the North China Craton. Our work also highlights the asynchronous nature of mantle and crustal extension during the post-collisional stage and provide important insights into the Wilson cycle.