Geochemical Markers of the Norilsk Ore-Bearing Intrusions: Case Study of the Maslovsky Deposit

Abstract

The problem of identifying scarce PGE–Cu–Ni-bearing intrusions among the huge array of barren mafic bodies in the northwestern Siberian Platform has been faced by researchers for several decades. Its solution is usually based on the geological and geophysical methods. Geochemical studies including modern elemental and isotopic analytical data are much less frequently applied for this purpose. We applied such an approach to some Norilsk complex bodies containing sulfide mineralization. Using the Maslovsky deposit located in the Norilsk syncline as an example, we have demonstrated the characteristic features of ore-bearing rocks that can be used in the search for new promising targets. The rocks of the Maslovsky deposit were studied in two sections from boreholes OM-4 and OM-24. Their geochemical parameters fall within the ranges of ε_Nd = 1.0 ± 1.0 and (La/Lu)_n = 2.3 ± 0.8, which differ the magmatic bodies of the Norilsk district with unique sulfide ores from barren massifs. The ⁸⁷Sr/⁸⁶Sr ratios in the representative gabbroic rocks from the vertical cross-sections of the Maslovsky deposit vary from 0.7056 to 0.7069. As PGEs are accumulated in the rocks, the Pd/Pt ratio increases from ~1 at clarke contents to ~3 in rich ores. No evidence of in situ assimilation by melts of silicate rocks was found.