Abstract:

The Hongqiling copper-nickel sulfide deposit mainly consists of No.1, No.2 and No.7 ore-bearing intrusions. The Re-Os isochron age of No.2 intrusion ((215.0±24.0) Ma) is consistent with zircon SHRIMP U-Pb age of the intrusion, (212.2±2.6 ) Ma, but the Re-Os isochron age of No.1 intrusion((237.0±16.0) Ma) is greater than zircon SHRIMP U-Pb age of the No.1 intrusion, (216.0±5.0) Ma. All these data indicate that Re-Os isochron ages of disseminated ores are not completely reliable. The Re-Os isochron age is greater than zircon SHRIMP U-Pb age, which is usually interpreted as crustal contamination inducing heterogeneity of Os isotopic. However, the research shows that No.1 and No.2 intrusions are mixed with some of the Earth’s crust substance, and the mixing volume of No.2 intrusion is slightly higher than that of the No.1 intrusion, which indicate that hybridization of crust materials is not the cause of heterogeneity in initial ¹⁸⁷Os/¹⁸⁸Os ratios, the major reason should be a further research. The initial ¹⁸⁷Os/¹⁸⁸Os ratios of No.1 and No.2 intrusions are 0.215±0.043 and 0.302±0.089, and γ_Os values range from 67.5 to 155.8 and 113.9 to 206.9, respectively, which indicate that the oreforming intrusions interfuse some crustal materials with possibly 20%-30% crustal Os contamination in Hongqiling area, and crustal materials might be the key factor to promote liquation ore formation.

Key words: Re-Os isotope, isochron age, Cu-Ni sulfide deposit, disseminated ore, Hongqiling