Abstract 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).

Abstract Isotope dilution thermal ionization mass spectrometry U–Pb dating and coupled Lu–Hf solution inductively coupled plasma mass spectrometry analyses of zircon were acquired from magmatic rocks along two transects across the Scandinavian Caledonides in the Troms–Ofoten region of Norway to explore possible correlations and gain insight into the evolution of far-travelled nappes within the Upper and Uppermost Allochthons. One pulse of magmatic activity was recorded at c. 489 Ma in the Tromsø Nappe. In the underlying Nakkedal Nappe, a magmatic pulse was recorded at c. 450 Ma, being contemporaneous with eclogite facies metamorphism in the area. Tonalites in the structurally underlying Lyngen and Gratangseidet ophiolitic complexes, both forming the substratum to carbonate–schist–quartzite sequences (Balsfjord and Evenes groups, respectively), yielded ages of 481 and 474 Ma. Obtained ɛ Hf(t) values are, however, distinctly different and indicate a juvenile origin for the Gratangseidet tonalite (ɛ Hf(474) =+9.57) and the presence of Palaeoproterozoic source material for the Lyngen tonalite (ɛ Hf(481) =−16.8 to −2.3). The 474 Ma age of the Snaufjellet granite intruding the Bogen Group structurally above the Evenes Group requires a thrust between the two units. An age of 435 Ma on the Heia gabbro of the Nordmannvik Nappe is comparable to that of the Råna norite (437 Ma) in the Narvik area, supporting a correlation with the Narvik Nappe Complex. The youngest intrusion dated to 425 Ma is a leucogranite that intruded the Balsfjord Group. The Lu–Hf data indicate a common source for several of the magmatic rocks in the Uppermost Allochthon, as well as Laurentian arc granitoids from East Greenland and possibly from Newfoundland and related areas.