Genesis of the Hongqiling No.7 magmatic Ni-Cu Sulfide deposit,Jilin,NE China

摘要

The Hongqiling No.7 intrusion hosts the second largest Cu-Ni sulfide deposit in China.It is a very small mafic-ultramafic intrusion (0.0078 km2 on the surface),but over 90 vol.％ of the intrusion has been mineralized.The intrusion is mainly composed of orthopyroxenite (95 vol.％),with minor peridotite and norite.All of the sulfide ores have extremely low PGE contents.Significantly low PGE contents and high Cu/Pd ratio (3×105 to 3×107) suggest the parental magma of the Hongqiling NO.7 intrusion lost PGE due to prior sulfide removal.All the rocks show LREE enrichment relative to HREE,strong negative Nb and Ta anomalies.Their εNd (t= 216Ma) values range from +3 to +5,and γOs values range from 85 to 187.Based on the Sm-Nd and Re-Os isotopic system,modeling results suggest that the mantle-derived magma experienced 10-20％ upper crustal contamination in a staging chamber.Due to crustal contamination,the magma reached S-saturation and Opx was crystallized from the magma.The sulfide concentration was mainly controlled by flowing differentiation in a magma conduit system.