Nickel Sulfide : The Primary Source of World Nickel Demand

Today, 56 % of global nickel production comes from nickel sulfide and only 42% comes from nickel laterite. Nickel sulfides are formed from the deposition of nickel minerals by hydrothermal fluids. This deposit is a family member of magmatic sulfide deposit wich consist of 2 types of deposit, i.e, 1) the nickel sulfides or so called Ni-Cu Sulfide because the nickel often associate with copper, and 2) the PGE (Platinum Group Element) dominant – magmatic sulfide which include valuable  mineral such as Platinum & Palladium.

 Magmatic Sulfide Deposit Occurance

 United States Geological Survey (USGS) recorded that formation of magmatic sulfide started with the partial melting of hot mantle rising as a plume from deep in the Earth to the earth crust. Then, the melting produces basaltic magma that is relatively rich in metals but may be poor in sulfur, which then rises upward and intrudes into the crust, forming magma chambers. In these chambers, basaltic magma may interact with the crust and become contaminated. Sulfur from surrounding rocks may be incorporated into the magma. This contamination reduces the ability of the magma to keep sulfur in solution and the magma may become sulfur saturated. When sulfur saturation occurs, droplets of sulfide liquid form; because the droplets are more dense than basaltic magma, they tend to settle into the lower part of the magma chamber. As the sulfide droplets segregate, they scavenge metals such as nickel (Ni), copper (Cu), and PGE such as platinum (Pt), and palladium (Pd) from the magma. If these sulfide droplets become sufficiently concentrated, a magmatic sulfide deposit is formed. The largest concentrations of sulfides appear to form in channels or conduits through which new magma flows into the magma chamber. Basaltic lavas erupted from chambers undergoing sulfide segregation will be depleted in those elements enriched in the sulfide deposits. Recognition of such depleted basalts can therefore provide important evidence that sulfide separation has occurred at depth.

 Ni-Cu Sulfide Deposit

 According Eckstrand and Hulbert from Geological Survey of Canada, Ni-Cu sulfide occur as sulfide-rich ores that are associated with differentiated mafic and/or ultrmafic sill and stocks, and ultramafic (komatiitic) volcanic flows and sills. In this type of deposit, Ni is the main economic commodity, generally at grades of about 1 to 3 percent. Copper may be either a coproductor by-product, and Co,PGE and Au are the usual by-product. However, in some cases, such as Norilsk in Russia, PGE may constitute highly significant coproduct.

The mafic and ultramafic magmatic bodies that host the Ni-Cu sulphide ores are diverse in form and composition, and can be subdivided into the following four subtypes:

1. A meteorite-impact mafic melt sheet that contains basal sulphide ores (Sudbury, Ontario is the only known example).
2. Rift and continental flood basalt-associated mafic sills and dyke-like bodies (Noril’sk-Talnakh, Russia; Jinchuan, China; Duluth Complex, Minnesota; Muskox, Nunavut; and Crystal Lake intrusion, Ontario).
3. Komatiitic (magnesium-rich) volcanic fl ows and related sill-like intrusions (Thompson, Manitoba; Raglan and Marbridge, Quebec; Langmuir, Ontario; Kambalda and Agnew, Australia; Pechenga, Russia; Shangani, Trojan, and Hunter’s Road, Zimbabwe).
4. Other mafic/ultramafic intrusions (Voisey’s Bay, Labrador; Lynn Lake, Manitoba; Giant Mascot, British Columbia; Kotalahti, Finland; Råna, Norway; and Selebi-Phikwe, Botswana).

Ore Characterisitic

 Eckstrand and Hulbert also explain that this deposit may occur as individual sulfide bodies associaated with magmatic mafic and/or ultramafic bodies. Other occur as groups of sulfide bodies associated wih one or morerelated magmatic bodies in areas or belts up to tens, even hundreds of kilometers long. Ni grades are tipically between 0.7 and 3 percent,and Cu grades ae between 0.2 and 2 percent. Ore tonnage of individual deposit range from few hundred thousands to a few tens millions. Two giant Ni-Cu deposit stand out above all the rest in the world are Sudbury in Ontario, Canada and Norilsk in Talnakh, Russia with ore tonnage of 1645 and 1903 Mt respectively. Other major Ni-Cu deposit are Thompson, Voisey’s bay and Raglan in kanada, Jinchuan in China, Kambalda in Australia and Pechenga in Russia.