Uplift of Paleozoic magmatic core complex in the Longshoushan area, Gansu: evidence from geochronology and geochemistry of rock veins in the Jinchuan deposit area

The Neoproterozoic Jinchuan Cu-Ni sulfide deposit is located in the central Longshoushan, southwestern margin of the North China Craton.Due to the tectonic compression and metamorphic hydrothermal superposition in the process of the Paleozoic orogeny, Cu-Pt-rich ores were enriched again.A large number of mafic-felsic rock veins and batholiths crop out in the Jinchuan deposit and its vicinity, which indicates existence of uplift of Paleozoic magmatic core complex in the Longshoushan area.This comprehensive study focuses on dolerite, lamprophyre, and granite porphyry veins crosscutting ore-bearing intrusions of the Jinchuan deposit area.Zircon U-Pb dating indicates that granite porphyry and lamprophyre formed at 367.1±2.0 Ma and 400.6~425.3 Ma, whereas the dolerite formed at 423.5±1.4 Ma based on previous work, preliminarily suggesting the Paleozoic formation ages for various types of rock veins in the deposit area.Petrochemical and isotope geochemical results show the dolerite and lamprophyre have ε_Nd(t)values ranging from -4.59 to -1.58 and -2.97 to -2.03, with corresponding (⁸⁷Sr/⁸⁶Sr)_i values of 0.7056 to 0.7077 and 0.7083 to 0.7085, respectively, indicating that the magma sources of these mafic rock veins were derived from an enriched lithospheric mantle.The granite porphyry has zircon ε_Hf(t)values of 5.11 to 12.84, suggesting it was sourced from partial melting of the juvenile crust.Combined with previous studies on regional Paleozoic magmatic activities, the authors put forward an integrated tectonic-magmatic evolution model.