岩石矿物学杂志2025，Vol.44Issue(5)：1225-1245,21.DOI:10.20086/j.cnki.yskw.2025.4216
柴北缘造山带鱼卡煌斑岩40Ar/39Ar年代学、地球化学特征及岩石成因
40Ar/39Ar geochronology,geochemistry characteristics and petrogenesis of lamprophyre from Yuka terrane,North Qaidam UHP metamorphic belt,NW China
摘要
Abstract
A series of lamprophyre dykes that crosscut the main foliation of the ultrahigh pressure(UHP)metamor-phic metapelite have been recently discovered in the Yuka terrane,North Qaidam Orogen,which are composed pre-dominantly of biotite/phlogopite,amphibole,K-feldspar and plagioclase.To investigate their petrogenesis and tec-tonic setting,systematic petrological,geochemical,mineral electron microprobe analyses and biotite40Ar/39Ar dat-ing 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 potas-sium(K2O/Na2O=1.72～4.41)and high Mg#(MgO=7.52％～9.90％,Mg#=66～72).They also exhibit enrich-ment 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 val-ues,while Nb/U ratios resemble global subducted sediment averages,indicating source metasomatism by mobile el-ements 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(logfO2)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 transi-tion zone(～70 km depth)within a metasomatized,high-oxygen fugacity enriched mantle.关键词
煌斑岩/柴北缘造山带/黑云母/结晶温度/造山后岩浆作用/鱼卡地体Key words
lamprophyre/North Qaidam Orogen/biotite/crystallization temperature/post-collisional magmatism/Yuka terrane分类
天文与地球科学引用本文复制引用
杨雪松,胡荣国,梁尚良,胡中天,杨云轩,吴杰,刘希军,洪路兵..柴北缘造山带鱼卡煌斑岩40Ar/39Ar年代学、地球化学特征及岩石成因[J].岩石矿物学杂志,2025,44(5):1225-1245,21.基金项目
国家自然科学基金项目(42073049) （42073049）
广西自然科学基金项目(2025GXNSFAA069323) National Natural Science Foundation of China(42073049) （2025GXNSFAA069323）
Natural Science Foundation of Guangxi Province(2025GXNSFAA069323) （2025GXNSFAA069323）
