Geochemical markers of the Norilsk ore-bearing intrusions: case study of the Maslovsky deposit

The problem of identifying rare PGE-Cu-Ni ore-bearing intrusions among the huge array of ore-free mafic bodies in the northwest of the Siberian Platform has been faced by researchers for several decades. For its solution, a complex of geological and geophysical methods is usually used. Geochemical studies based on modern analytical data, such as elemental and isotopic data, are much less frequently used for this purpose. We used such an approach in the study of some Norilsk complex bodies containing sulfide mineralization. The example of the Maslovskoy deposit located in the Norilsk basin demonstrates the characteristic features of ore-bearing rocks that can be used in the search for new promising targets. For the rocks of the Maslovskoy deposit, represented by two sections from cores OM-4 and OM-24, geochemical parameters were obtained that fit into the ranges of εNd= 1.0 ± 1.0 and (La/Lu)n= 2.3 ± 0.8, which distinguish the magmatic bodies of the Norilsk ore region with unique sulfide ores from the barren ones. The87Sr/86Sr ratios in the representative gabbroic rock’s samples of the vertical cross-sections of the Maslovskoy deposit vary from 0.7056 to 0.7069. As PGE accumulate in the rocks, the Pd/Pt ratio increases from ~1 at clarke-level contents to ~3 in rich ores. No evidence of assimilation by melts of silicate rocks in situ was found.