Fe-Ti Basalts, High Silica Rhyolites, and the Role of Magmatic Heat in the Genesis of the Kam-Kotia Volcanic-Associated Massive Sulfide Deposit, Western Abitibi Subprovince, Canada
C. Tucker Barrie, John Pattison, 1999. "Fe-Ti Basalts, High Silica Rhyolites, and the Role of Magmatic Heat in the Genesis of the Kam-Kotia Volcanic-Associated Massive Sulfide Deposit, Western Abitibi Subprovince, Canada", The Giant Kidd Creek Volcanogenic Massive Sulfide Deposit, Western Abitibi Subprovince, Canada, Mark D. Hannington, C. Tucker Barrie
Download citation file:
The Kam-Kotia volcanic-associated massive sulfide deposit (6.4 million tons, 1.1% Cu, 1.2% Zn, 0.1 oz/t Ag) is the largest of four deposits in the Late Archean Kamiskotia district. It occurs within a 4-km-thick bimodal stratigraphy, 2 km above a cogenetic and coeval gabbroic complex and accompanying fel-sic intrusion.
The composition and nature of the mafic and felsic volcanic rocks change from the stratigraphic foot-wall to the hanging wall in the Kam-Kotia mine area. Fe-Ti basalts—iron, titanium, and incompatible element-enriched tholeiitic basalts—are volumetrically minor in the footwall where they occur only as relatively thin (<5 m) sills and dikes. The ore horizon is cut by Fe-Ti basalt sill-flow units with peperite-textured upper contacts locally. In the hanging wall, Fe-Ti basalt units occur as 20- to 200-m-thick flows. The thickest of these are immediately upsection from the Kam-Kotia ore horizon and suggest ponding in a topographic depression. Two distinctive, mafic lapilli-bearing, intermediate and felsic tuff units are present along strike with, and ∼100 to 200 m upsection from, the Kam-Kotia ore horizon and are traceable for 5 km along strike. The mafic lapilli fragments are tholeiitic and approach Fe-Ti basalt compositions, and they have quenched rims and popcorn- or fiammelike textures. These units represent mixed magma, Plinian-type eruptions in a relatively shallow subaqueous setting. Rhyolite units change compositionally across the ore horizon, with potassic- and rubidium-enriched rhyolite units present almost exclusively in the stratigraphic hanging wall.
Calculated magmatic temperatures decrease in the vicinity of the ore horizon, as documented by the MgO thermometer for mafic rocks and the zircon saturation geothemometer for felsic rocks. Least altered tholeiitic mafic rocks are principally in the footwall, with Mg/(Mg + Fe) 45 to 58 and estimated temperatures of 1,130° to 1,210°C (n = 67). Hanging-wall Fe-Ti basalts have Mg/(Mg + Fe) of 30 to 44 and lower temperatures of 1,080° to 1,130°C (60 of 65 samples). Ferroan tholeiitic basalts have Mg/(Mg + Fe) and temperatures that overlap with the other basalt types and are ubiquitous. For least-altered rhyolites that approximate liquid compositions, the highest temperatures of 940° to 980°C are calculated for samples within 250 m of Kam-Kotia ore horizon (32 of 36 samples), whereas almost all others have lower temperatures of 850° to 940°C.
During the time of metal deposition, shallow-level fractionation of a tholeiitic parent produced Fe-Ti basalt magmas, as recorded in the ferroan upper zone cumulates of Kamiskotia Gabbroic Complex. Mafic magmas cooled with fractionation, assisted by advective heat loss by convecting hydrothermal fluids. Fel-sic magma temperatures increased at this time due to increased proximity and conductive heat from the adjacent mafic magma chamber, and to mafic magma injections as recorded by the mixed magma tuffs, and decreased afterward. Extrusion of Fe-Ti basalts apparently quenched the sulfide-precipitating system responsible for the Kam-Kotia deposit and the other volcanic-associated massive sulfide deposits of the Kamiskotia district.
Figures & Tables
The Giant Kidd Creek Volcanogenic Massive Sulfide Deposit, Western Abitibi Subprovince, Canada
ARCHEAN Cu-Zn deposits are among the most important mineral deposit types in Canada. The Superior province of Canada contains nearly 80 percent of the known Archean Cu-Zn deposits in the world (about 100 of 125 deposits). These deposits are concentrated in 10 separate mining camps, including Sturgeon Lake, Manitouwadge, Mattagami Lake, Chibougamau, Joutel, Val d’Or, Bous-quet, Noranda, Kidd Creek, and Kamiskotia (Fig. 1 and Table 1). A few deposits in rocks of similar age and composition are also known in the Slave province, the Churchill province, and in the Archean of Western Australia, southern Africa, China, and Brazil. Known deposits of this age worldwide account for more than 650 million metric tons (Mt) of massive sulfides, containing 10 Mt of Cu metal, 29 Mt of Zn, 1 Mt of Pb, 33 Mkg Ag, and 750,000 kg Au. The giant Kidd Creek volcanogenic massive sulfide deposit in the western Abitibi subprovince of Canada is the largest known deposit of this age currently in production. The Superior province is the world’s largest exposed Archean craton, occupying an area of more than 1.5 million km2, bounded by the Trans-Hudson orogen to the west and the Grenville province to the east. A number of distinct subprovinces are recognized, assembled into east-west-trending granite-greenstone terranes and metasedi-mentary belts (Fig. 1). The granite-greenstone terranes are composed of gneissic rocks of plutonic origin, supracrustal rocks of dominantly volcanic origin, and a variety of syn- to late kinematic granitoids. Volcanic rocks comprise about 12 percent of the total area. The greenstone belts have been described variously as successive lateral accretions of volcano-plutonic arcs, oceanic islands, oceanic plateaus, and rift-related assemblages (e.g., Langford and Morin, 1976; Percival and Card, 1985; Ludden and Hubert, 1986; Ludden et al., 1986; Card, 1990; Jackson and Sutcliffe, 1990; Williams, 1990; Corfu, 1993; Heather et al., 1995; Jackson and Cruden, 1995). The metallogenic history of the Superior province has been described in detail by Franklin and Thorpe (1982) and Poulsen et al. (1992).
The Abitibi subprovince (94,000 km2) is the largest of the greenstone belts. It contains the major gold and base metal mining camps in Canada (Fig. 2), with production and reserves totaling more than 480 Mt of massive sulfide and 4,700 t of Au. Metal production in the western portion of the Abitibi greenstone belt is dominated by the Timmins region, which historically has accounted for 37 percent of the total gold production