Structural control of gold mineralization at the Sigma Mine, Val d'Or, Quebec

Abstract The Sigma gold deposit is in a band of deformed metavolcanic rocks that are cut by an irregular mass of porphyritic diorite and by narrow undeformed feldspar porphyry dykes. The gold is in veins consisting mainly of quartz and tourmaline with minor pyrite, carbonate, chlorite, scheelite and free gold. The results presented here concern the structural setting of the ore and are based on a study of the mode of emplacement.
Two principal types of veins have been recognized: sub-vertical and oblique veins. Both types are contemporaneous, mechanically linked and postdate regional deformation. The sub-vertical veins are composed of numerous mineralized lenses that occupy the central part of ductile shear zones of great lateral and vertical extent. Normally, several lenses occur in the same shear zone. The vein material seems to have resulted from incremental filling of openings by repeated vertical movement along rupture planes developed in the central part of the shear zones.
The oblique veins are small elliptical lenses of ribboned vein material which formed essentially by progressive vertical opening of oblique fractures. Two types of oblique veins are known: one is restricted to feldspar porphyry dykes, within which they are arranged in an en-echelon fashion; the other is of greater extent and is not restricted to one rock type, but tends, however, to occur in the more competent porphyritic diorite.
Vein orientation and mode of formation suggest that both sub-vertical and oblique veins developed during progressive deformation associated with the formation of the ductile shear zones. The latter probably formed in response to a compression that took place late in the tectonic history of the host rocks at Sigma.
Keywords: Gold deposits, Abitibi gold deposits, Sigma Mine, Mineralization, Structural geology, Veins, Shear zones.
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Summary: This paper describes the use of vector analysis for determining the intersection of mineral deposit veins. The mathematical evolution of the analysis is outlined.
Publication: CIM Bulletin
Author(s): J.H. ARCHIBALD
Keywords: Mineral exploration, Vector equations, Veins, Drilling, Mathematics, Coordinate system.
Issue: 850
Volume: 76
Year: 1983
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Summary: Occupational health programs and their role in improving the quality of working life in the mining industry are discussed. Attention is directed to some problems peculiar to the Canadian mining industry. Factors affecting program development are reviewed, as well as parameters affecting cost-benefit analyses.
Publication: CIM Bulletin
Author(s): IAN M.F.ARNOLD
Keywords: Health, Occupational health, Safety, Working life, Physicians, Medical services.
Issue: 850
Volume: 76
Year: 1983
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Summary: This paper describes the nature of stage curves and the ways in which they have been used to study the construction sequencing of tailings impoundments. They provide a simple graphical method of representing the main aspects of an impoundment, studying the effects of different impoundment geometries, and predicting and controlling impoundment operations.
Publication: CIM Bulletin
Author(s): JACK A. CALDWELL
Keywords: Environmental control, Stage curves, Dams, Tailings dams, Elevation-capacity curves, Production rate curves, Rate-of-rise curves.
Issue: 850
Volume: 76
Year: 1983
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Summary: Heap leaching, currently being applied in the treatment of low-grade ores in the southwestern United States, is shown to have potential for use in northwestern Ontario. The history and operation of the process are described, and cost comparisons are given.
Publication: CIM Bulletin
Author(s): R.C. BEARD
Keywords: Leaching, Heap leaching, Gold deposits, Mineral processing, Porosity, Column leaching, Sodium cyanide, Cyanidation.
Issue: 850
Volume: 76
Year: 1983
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Summary: Next month will mark the anniversary of the release of an important federal study on a mineral policy for Canada. The study, entitled "Mineral Policy—A Discussion Paper", provides well-researched coverage of a broad range of issues that are of interest to the mining industry. Unfortunately, there is a real possibility that the discussion paper will wither and die on the vine, unless the federal and provincial governments, and the private sector, collectively ensure that some...
Publication: CIM Bulletin
Author(s): ROBERT B. PARSONS
Issue: 850
Volume: 76
Year: 1983
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Summary: Proterozoic plutonic and volcanic rocks in the Franklin Mountains, west Texas, exhibit similar values in average concentrations of equivalent uranium (ell), equivalent thorium (eTh) and equivalent potassium (eK) when compared to Proterozoic igneous rocks of the southwestern United States. Variations of radioelement concentrations for all Proterozoic igneous rocks of the Franklin Mountains range from 1.1 to 357.1 ppm U, 2.1 to 259.1 ppm Th and 2.5 to 10.2% K.
Recent geologic mapping of the...
Publication: CIM Bulletin
Author(s): WILLIAM F. THOMANN, ARTHUR J. PYRON, DAVID R. RAY
Keywords: Uranium, Thorium, Potassium, Franklin Mountains, Texas, Variation diagrams, Proterozoic rocks, Radioelements, Tin deposits.
Issue: 850
Volume: 76
Year: 1983
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Summary: The Monkman Coal Property is located in the Northeast Coal Block of British Columbia. It is divided into the Duke Mountain Block on the northeast and the Dip Slope on the west. Together, these areas cover 39,503 ha of coal licences.
The property is underlain by Jurassic and Lower Cretaceous marine and continental sedimentary rocks. Economic coal measures are contained within the Gates Formation. Exploration of the property began in the early 1970s, with drilling commencing in 1975. To date,...
Publication: CIM Bulletin
Author(s): E.A. SCHILLER, S.P. SANTIAGO, W.A. PLACHNER
Keywords: Coal, Monkman deposit, British Columbia, Duke Mountain Block, Gates Formation, Exploration, Geology, Resources, Reserves.
Issue: 850
Volume: 76
Year: 1983
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Summary: The main objective of ore grinding is to liberate the valuable minerals from the gangue so that afterwards concentration can be easily achieved with the best yield. The current practice is to try to maintain constant the particle size distribution of the grinding product. Unfortunately, the textural properties of ore minerals present natural variations in a deposit and this practice does not necessarily lead to a constant ore liberation. Thus, for optimal performance of the concentration...
Publication: CIM Bulletin
Author(s): M.A. BERUBE, J.C. MARCHAND
Keywords: Traitement du minérai, Analyse d'images, Libération des minérais, Vroyage, Degré de libération, Traitement des données, Automatisation
Issue: 850
Volume: 76
Year: 1983
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Summary: Rocks with abundant aluminum silicate minerals occur in two ways adjacent to stratabound pyritic gold occurrences within mafic tuffs at the Bousquet Mine, Abitibi Belt, Quebec:
1) A weakly laminated rock composed of quartz, muscovite, andalusite, kyanite, pyrite, pyrophyilite, diaspore and chlori-toid is discordant within tuff footwall to a pyritic gold occurrence and is traversed locally by quartz-kyanite veinlets. This rock is SiO2-, Al2O3- and K2O-rich relative to enveloping tuff, although...
Publication: CIM Bulletin
Author(s): R.I. VALLIANT, R.L BARNETT, R.W. HODDER
Keywords: Gold deposits, Abitibi gold deposits, Aluminous rocks, Mineralization, Bousquet Mine, Blake River Group, Stratiform deposits, Hydrothermal alteration, Mineral analyses.
Issue: 850
Volume: 76
Year: 1983
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