Geochemical Features and Mineral Associations of Differentiated Rocks of the Norilsk 1 Intrusion

Nadezhda Tolstykh,Vladimir Korolyuk,Gennadiy Shvedov,Aleksandr Polonyankin

doi:10.3390/min10080688

Abstract

The purpose of this study is to show the patterns of distribution of disseminated sulfide in layered rocks based on the numerous geochemical and mineralogical data obtained for eight boreholes of the Norilsk intrusion (southern part of the Norilsk 1 deposit). There is a common trend of sulfide liquid fractionation in the Main Ore Horizon, which is composed of picritic and taxite (or olivine) gabbro-dolerites: the Ni/Cu in both rock types decreases down all sections, indicating an increase in the degree of fractionation of the sulfide liquid from top to bottom. On the contrary, the Ni/Fe ratios in pentlandite increase in this direction due to an increase in sulfur fugacity. However, picrite and taxite/olivine gabbro-dolerites are very distinctly separated by Ni/Cu values: these values are >1 in picritic gabbro-dolerite while they are always <1 in taxite/olivine gabbro-dolerite. These rock types are distinguished by sulfide assemblages. The first includes troilite, Fe-rich pentlandite, chalcopyrite, cubanite, talnahite, bornite and copper (low sulfur association); the second one is composed of monoclinic pyrrhotite, chalcopyrite, Ni-rich pentlandite and pyrite (high sulfur association). A two-stage magma injection with different ore specializations is supposed for picritic and taxite/olivine gabbro-dolerites.

Highlights

The platinum–copper–nickel deposits of the Norilsk District are located in the northwestern part of the Siberian platform and are associated with the flood basalt of the Permian–Triassic age [1–3]
1) General patterns of mineralogical-geochemical regularities exist in the distribution of ore elements along the cross-sections of all boreholes: a) the Ni/Cu ratios decrease in the rocks with depth; 2) the Pd/Pt ratios show sawtooth patterns, but, in general, they increase with depth, whereas typomorphic features are observed for each rock layer: a) Ni/Cu is more than one in picritic gabbrodolerite, whereas Ni/Cu is less than one in olivine gabbro-dolerite; b) contents of ore elements prevail
(1) General patterns of mineralogical-geochemical regularities exist in the distribution of ore elements along the cross-sections of all boreholes: (a) the Ni/Cu ratios decrease in the rocks with depth; (2) the Pd/Pt ratios show sawtooth patterns, but, in general, they increase with depth, whereas typomorphic features are observed for each rock layer: (a) Ni/Cu is more than one in picritic gabbro-dolerite, whereas Ni/Cu is less than one in olivine gabbro-dolerite; (b) contents of ore elements prevail in taxite gabbro-dolerites compared to picritic ones (Figure 3b–d), while they are higher in picritic gabbro-dolerite than in the underlying olivine gabbro-dolerite

Summary

Introduction

The platinum–copper–nickel deposits of the Norilsk District are located in the northwestern part of the Siberian platform and are associated with the flood basalt of the Permian–Triassic age [1–3]. The Norilsk 1 intrusion intruded into the Carbonian–Permian terrigenous stratum of the Tungusska Series and basalts of the Upper. The focus was on the study of promising massive ores [4–22] or low-sulfide horizons [23–30] which are localized in taxitic gabbroic rocks and leucocratic gabbro of the “Upper gabbro series” [29] of Norilsk deposits. The disseminated ores in the Norilsk deposits are less studied [10,11,31–33]. The patterns of distribution of ore elements in differentiated series of different rocks, the composition of disseminated sulfide ores and changes in the modes of occurrence of base and noble metals are of scientific and promising interest

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Discussion

Conclusion