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The Archean Superior Province of the Canadian Shield and Its Lode Gold Deposits*

By
K. D. Card
K. D. Card
Lithosphere and Canadian Shield Division, Geological Survey of Canada, 588 Booth Street, Ottawa, Ontario, Canada K1A 0E4
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K. HOWARD Poulsen
K. HOWARD Poulsen
Mineral Resources Division, Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario, Canada K1A 0E8
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Francois Robert
Francois Robert
Mineral Resources Division, Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario, Canada K1A 0E8
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Published:
January 01, 1989

Abstract

The Superior province, a major Archean craton of the Canadian Shield, was formed during middle and late Archean tectono-magmatic events from rocks of mantle or recycled juvenile crustal origin assembled by accretionary mechanisms in convergent tectonic settings. The Superior province consists of northern and southern high-grade gneiss terranes and a broad central region of alternating lower grade greenstone- and metasediment-rich subprovinces, all intruded by voluminous granitoid plutons. Subprovince boundaries are complex zones of facies, metamorphic, and structural transition, commonly telescoped by crustal-scale faults. Volcanism, plutonism, and sedimentation occurred at ca 3.1 to 2.8 Ga, notably in the north, and again at ca 2.75 to 2.7 Ga throughout the Superior province, in settings analogous to modern oceanic island arc-interarc basin-accretionary wedge systems. Polyphase deformation, metamorphism, and plutonism at ca 2.7 Ga, all products of subduction-driven accretion, resulted in ductile deformation and granulite facies metamorphism at deep crustal levels represented by the high-grade gneiss terranes and in ductile to brittle deformation and lower grade metamorphism at high crustal levels represented by the greenstone-granite subprovinces. Lode gold deposits formed during late ductile-brittle stages of deformation are related to major fault systems and to zones of rock alteration within greenstone-granite subprovinces. Granulite metamorphism at depth, involving dehydration and formation of HO2 and CO2-rich fluids, was synchronous with brittle deformation, rock alteration, and formation of lode gold deposits at high crustal levels. Although granulitization models probably best account for most genetic aspects of the Superior province lode gold deposits except their confinement to greenstone-granite terranes, degree of greenstone belt preservation is an important factor in their present distribution.

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Economic Geology Monograph Series

The Geology of Gold Deposits: The Perspective in 1988

Reid R. Keays
Reid R. Keays
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W. R. H. Ramsay
W. R. H. Ramsay
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David I. Groves
David I. Groves
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Society of Economic Geologists
ISBN electronic:
9781629490014
Publication date:
January 01, 1989

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