西昆仑岔路口马鞍山铜镍矿化辉长岩成因:来自元素地球化学和Sr-Nd-S同位素的制约OA

The Triassic mafic-ultramafic complex at Maanshan in the Chalukou area of the West Kunlun,Xin-jiang,represents a recently discovered copper-nickel mineralization occurrence.However,its petrogenesis and ore-forming potential remain poorly constrained.This study conducts systematic petrographic,whole-rock geo-chemical,Sr-Nd isotopic,and in situ sulfur isotopic analyses of sulfide minerals from the Maanshan gabbro,aiming to reveal its magmatic evolution,source characteristics,tectonic setting,and sulfur saturation mecha-nisms,thereby enhancing the understanding of regional magmatism and mineralization processes and providing insights for prospecting breakthroughs.The gabbro exhibits right-inclined chondrite-normalized rare earth ele-ment patterns with light rare earth element enrichment and heavy rare earth element depletion.Its trace element signatures show enrichment in high field strength elements(e.g.,Nb,Ta)and depletion in large ion lithophile el-ements(e.g.,Ba,K),consistent with ocean island basalt(OIB)affinities.Elevated(Th/Yb)PM ratios(1.35-7.10)and low ratios of Ce/Pb(10.74-22.51),and Nb/Ta(12.27-16.05)indicate significant crustal contamination.Pos-itive correlations between MgO and Cr/Ni suggest fractional crystallization of olivine and clinopyroxene during magmatic evolution.Whole-rock initial(87Sr/86Sr)i ratios range from 0.703 50 to 0.703 58,with εNd(t)values of+5.0 to+5.5,reflecting a strongly depleted mantle source.Low ratios of La/Nb(0.80-1.17),La/Ta(10.3-14.6),and Dy/Yb(2.16-2.43)further suggest that the primary magma was derived from a depleted asthenospheric mantle dominated by peridotite.Positive δNb values(0.13～0.14)and high mantle potential temperatures(Tp=1 574-1 616 ℃)of the Maanshan gabbro,combined with regional basaltic magmatism and deep-marine volcanic-sedi-mentary sequences,support a tectonic setting related to mantle plume activity,analogous to ocean island-seamount basalts.In situ δ34S values of disseminated pyrite and chalcopyrite range from+3.27‰ to+4.23‰ and-3.59‰ to-2.06‰,respectively,deviating from typical mantle sulfur values and indicating that crustal contami-nation was the primary mechanism triggering sulfur saturation and sulfide segregation.The occurrence of sur-face annabergite together with the relatively low M/F ratio(0.94-1.15)of the gabbro in the Maanshan intrusion suggests favorable prospecting potential at depth,warranting further exploration.