Magma Evolution And Sulfide Mineralization Of The Karatongk Ni-Cu Sulfide Deposit, Xinjiang, China

The Karatongk deposit Ni-Cu sulfide deposit is hosted by several mafic-ultramafic intrusions in northern Xinjiang,China.This study investigate magma evolution and oregenesis of the sulfide-bearing intrusions including Karatongk 1^#,2^#and 3^# intrusions using mineral compositions and whole rock compositions including major and trace elements and platinum group elements(PGE).Preliminary results are summarized below.Whole rocks of the sulfide-bearing intrusions are characterized by elevated MgO and FeO,and lower Na₂O+K₂O and TiO₂ than typical tholeiitic basalts.They are also characterized by enrichments in large ion lithophile elements(LILE)and light rare earth elements(LREE),and depletions in high field strength elements(HFSE)and relative to primitive mantle and MORB.No significant Eu anomalies are observed in the samples.Depletions of Nb and Ta in the samples indicate assimilation during magma evolution.The parental magma of the intrusions is likely of tholeiitic basalts based on crystallization sequence and whole rock geochemical data.Sulfide saturation in the magmas may be related to olivine crystallization and contamination with crustal materials in the staging magma chamber.High sulfide/magma ratio in Karatongk 1^# intrusion suggests that much of the sulfide were transported as immiscible sulfide droplets by magma from depth.In contract,minor sulfide mineralization at the base of Karatongk 3^# is consistent with in situ sulfide liquid segregation and gravitational setting.Both processes appear to be important in Karatongk 2^# intrusion in which sulfides are concerned in the western rim of the intrusion as well as at the base of the intrusion.