Guest Column (October 07, 1991)

The visit earlier this year by University of Toronto professor Tony Naldrett and myself to the Noril’sk mining camp in Siberia was arranged by the Soviet Academy of Sciences and hosted by the Noril’sk Kombinant.

Noril’sk is probably the richest and largest known deposit of nickel, copper, and platinum group elements in the world (grade and tonnage figures have never been published). The program of investment on which Lenin embarked, and Stalin continued, now accounts for the significance of Noril’sk to the Soviet economy. Despite its reputation as one of the more notorious gulag archipelagoes, Noril’sk is now a major city of over 200,000 people. The standard of living is high. (The rate for a basic underground driller is almost US$1,000 per month, at present official exchange rates, which compares with the average wage of a Muscovite of some US$100.)

The nickel-copper-platinum group element deposits of the Noril’sk region occur principally along the Noril’sk Kharayelakh fault. These deposits are mined from two intrusions, the Noril’sk I intrusion located south of Noril’sk City, and the Talnakh intrusions located north of Talnakh City. In some places, the massive sulphide (i.e. 100% sulphide) reaches 50 metres thick and extends for several kilometres along strike. The sulphide occurs principally at the base of the intrusion and is frequently hosted in sediment. The ore is heavily zoned from copper-rich talnakhite to nickel-rich pentlandite-pyrrhotite ores.

The Noril’sk deposit is worked by open pit methods at Bear’s Brook, which we visited. The intrusion dips gently south and the pit has gradually migrated south and deepened in order to tap the rich massive ores at the base of the intrusion.

The Talnakh intrusion is worked from six mines. Two additional mines are under development (Svernij and Glubokij). We visited the Taimyr mine on the western extension of the Oktybar’sk deposit. Here the sulphides dominantly follow the lower contact where they are hosted in sediments of the Tunguska series. There is very little disseminated ore in the gabbrodolerite above the massive ore. The thickness of the gabbrodolerite is less than 200 metres. Most of the intrusions host some disseminated sulphide, but in most cases the disseminated sulphide is not exploited.

The volume of nickel sulphide developed is significantly greater (by a factor of over 50 times) than the volume of sulphide that the silicate magma of the intrusion could carry. There is a strong suggestion that much of the sulphide was introduced at the base of the intrusion as an influx of magmatic sulphide which was derived from a significantly larger volume of magma at depth. It means that we need not constrain exploration models in flood basalt provinces to large intrusions. Indeed, as pointed out by Naldrett in an address to the Society of Economic Geologists in May, the Talnakh intrusion is no larger than many of the smaller Nipissing diabase sills or dolerites of the Keweenawan.

The environmental impact of mining activities north of the Arctic Circle are profound. Some 80 scientists and technicians have been employed in the laboratories to understand the ecological effects of sulphur emissions and tailings. Exploration activity has played havoc with the sensitive low arctic tundra ecosystem. Vast slag and tailings ponds are eroded by the wind, and methods of stabilizing them have only just been implemented. Due to the permafrost conditions, all services and piping must travel across the surface and slowly sink into a quagmire of mud. Areas that have been stripped are desolate as the tundra vegetation is very slow to stabilize under such conditions.

The Noril’sk area has been extensively drilled and mapped by the Noril’sk Expedition of the Ministry of Geology. The present workings are only a small fraction of the total reserves in the Noril’sk intrusions.

A Sudbury-Noril’sk symposium is being planned to take place in Sudbury, Ont., in the fall of 1992 and will consist of three days of papers. The first day, papers presented by invited Soviet speakers will describe the geology of the Noril’sk region and the mineral deposits. The second day will be devoted to the geology of the Sudbury Igneous Complex. The third day will incorporate other papers on Noril’sk and Sudbury.