Platinum-group elements characteristics of the Hejiaya Ni-Co intrusion in the south of Lüeyang County, Shaanxi Province: Constraints on the process of sulfide melting segregation

Hejiaya Ni−Co mineralized intrusion is located in Bikou block of South Qinling. It is one of the important new discoveries of nickel, cobalt and other strategic minerals in Qinling orogenic belt in recent years.The rock mass is mainly composed of gabbro, gabbro−diorite and a small amount of pyroxenite, amphibolite, and the mineral bodies is mainly hosted by the altered gabbro.Based on the analysis of platinum−group element geochemistry and in situ sulfur isotope of sulfide in ores of different structural types, the magmatic properties and the process of sulfide melting segregation are discussed. The results showed that the abundance of platinum−group elements (PGE) was low in all kinds of ores (3.93×10⁻⁹ ~ 87.85×10⁻⁹, average 27.88×10⁻⁹). The geochemical characteristics of platinum−group elements indicate that the primary magma of the rock mass is high magnesium basaltic magma, which is weakly affected by the late hydrothermal process. The characteristics of platinum−group elements and in situ sulfur isotopes indicate that the separation and crystallization of mafic minerals is an important factor that causes sulfur evolution to saturation and deep sulfide melting segregation.The significant depletion of Pt element in the ore may be the result of Pt−containing mineral crystallization. The Lüeyang Hejiaya rock mass in South Qinling has good Ni−Co metallogenic conditions and prospecting potential, which is expected to make a major breakthrough in the exploration and evaluation of magmatic Cu−Ni sulfide deposit in Qinling orogenic belt.