Nickel-copper sulphide deposits are sulphide concentrations that occur in certain mafic and/or ultramafic intrusions or volcanic flows. Nickel is the main economic commodity, copper may be either a coproduct or byproduct, and platinum group elements (PGEs) are usual byproducts. Other commodities recovered in some cases include gold, silver, cobalt, sulphur, selenium, and tellurium. These metals are associated with sulphides, which generally make up more than 10% of the ore. The locations of Canadian depos-its are shown in Figure 27.1-1.

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

(27.1a) an astrobleme-associated sill-like mafic intrusion that contains ores in which Ni:Cu is approximately 1:1 (Sudbury, Ontario is the only known example).

(27.1b) rift- and continental flood basalt-associated mafic sills and dyke-like bodies, in which Ni:Cu ratios of the related ores may be either somewhat greater or less than 1 (Noril’sk-Talnakh, Russia; Duluth Complex, Minnesota; Crystal Lake intrusion, Ontario; possibly Jinchuan, China).

(27.1c) komatiitic volcanic flows and related intrusions, which have ores with Ni:Cu ratios that are commonly greater than 10, but less in some cases (Thompson, Manitoba; Expo Ungava and Marbridge, Quebec; Langmuir, Ontario; Kambalda and Agnew, Australia; Pechenga, Russia; Shangani, Trojan, and Hunter’s Road, Zimbabwe; Kabanga, Tanzania).

(27.Id) other tholeiitic intrusions, in which the Ni:Cu ratios of the ores are commonly in the range 2 to 3 (Lynn Lake, Manitoba; Giant Mascot, British Columbia; Kotalahti, Finland; Râna, Norway; Selebi-Pikwe, Botswana).