Genesis of the Permian Kemozibayi sulfide-bearing mafic-ultramafic intrusion in Altay, NW China: Evidence from zircon geochronology, Hf and O isotopes and mineral chemistry

摘要: Abstract The recently discovered Kemozibayi mafic-ultramafic intrusion and its associated magmatic Cu-Ni sulfide deposits are located at the southern margin of Chinese Altai Mountain, Central Asian Orogenic Belt in north Xinjiang, NW China. is composed olivine websterite, norite, gabbro diorite. Disseminated net-textured Ni-Cu ores hosted center gabbro. In this work, new zircon U-Pb ages, Hf-O isotopic S data, whole rock mineral chemical analyses combined order to elucidate characteristics mantle source, nature subduction processes, degree crustal contamination, geodynamic setting bimodal magmatism region, metallogenic potential economic deposit depth. SIMS dating yields Permian ages (278.3 ± 1.9 Ma), coeval with Kalatongke Eastern Tianshan Beishan areas. Several lines evidence (positive eHf(t) from + 7.1 + 13.3, Al2O3, TiO2 SiO2 contents clinopyroxene high contents) suggest that primary magma was a calc-alkaline basaltic derived depleted mantle, partial melting source high. evolution complex strongly controlled by fractional crystallization sequence then This evidenced Fe2O3 positively correlated MgO negatively CaO Na2O, similar LREE enrichment negative Nb, Ta, Hf anomalies chondrite primitive mantle-normalized patterns, decrease total REE trace elements magnetite content through norite websterite. Varied low (+ 7.1 + 13.3) δ18O values (+ 6.4‰ + 7.2‰) zircon, La/Ba, Rb/Y ratios, Nb/La ratios samples, 5–10% contamination related fluid 10–15% contribution an upper component. Alz (percentage tetrahedral sites occupied Al) show rift cumulate rocks, but minor arc features, indicating might have experienced lower metasomatism. A subducted oceanic sediments metasomatism appropriate for formation copper nickel deposit. Crustal addition early fractionation induced saturation immiscible intrusion. With no obvious Ni-rich co-crystallization, Cu grade present orebody higher than Ni grade, proportion mafic rocks complex. Cumulatively, these features underwent segregation, deeper or extended portions intrusive body may host mineralization.