A series of lamprophyre dykes that crosscut the main foliation of the ultrahigh pressure (UHP) metamorphic metapelite have been recently discovered in the Yuka terrane, North Qaidam Orogen, which are composed predominantly of biotite/phlogopite, amphibole, K-feldspar and plagioclase. To investigate their petrogenesis and tec-tonic setting, systematic petrological, geochemical, mineral electron microprobe analyses and biotite ⁴⁰Ar/³⁹Ar dating have been performed on two lamprophyre samples. Bulk-rock geochemistry reveals that the Yuka lamprophyres are potassic calc-alkaline types, which are characterized by medium SiO₂ content of 55.19%~55.78%, high potassium (K₂O/Na₂O=1.72~4.41) and high Mg^# (MgO=7.52%~9.90%, Mg^#=66~72). They also exhibit enrichment in light rare earth elements (LREE) and large ion lithophile elements (LILE, e.g., Rb, Ba, Pb), coupled with depletion in heavy rare earth elements (HREE) and high field strength elements (HFSE, e.g., Nb, Ta, Ti), displaying typical subduction signatures. Nb/Ta ratios fall between continental crust and the primitive mantle values, while Nb/U ratios resemble global subducted sediment averages, indicating source metasomatism by mobile elements rich subduction fluids. Mineral geochemistry analysis show that phlogopite relics in phenocrystic biotite,phenocrystic biotite, and matrix biotite crystallized at temperatures of 1 098~1 167℃, 1 054~1 106℃ and 1 049~1 101℃, respectively. Their crystallization pressures are 1.62~2.12 GPa, 1.51~1.63 GPa, and 1.57~1.66 GPa, respectively. The calculated oxygen fugacity (log f_O2) ranges from -4.42 to -5.90, -5.80 to -6.71, and -5.84 to -6.67 for these phases, suggesting a high oxygen fugacity environment. Biotite/phlogopite from the lamprophyre analysed by ⁴⁰Ar/³⁹Ar laser step-heating dating yielded a plateau age of ca. 360 Ma, indicating the dike formed in the Late Devonian to Early Carboniferous. Taken together with field occurrence, whole-rock and mineral geochemical characteristics, geochronology and regional tectonics, we propose that the Yuka lamprophyre formed in a post-collisional lithospheric extensional tectonic setting during the North Qaidam Orogen evolution, which likely originated from partial melting of phlogopite-bearing spinel facies iherzolite at the garnet-spinel transition zone (~70 km depth) within a metasomatized, high-oxygen fugacity enriched mantle.