Quinsam and Chute Creek Coal Deposits (NTS 092F/13,14)
Paper 1991 - 3
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Paper 1991-3 covers part of an ongoing project that was begun in 1987 to bring knowledge of the Vancouver Island coal deposits up to date. The aim of these resource evaluation studies is to provide sufficient data and analysis to assist industry and government in assessing the potential of the Island coals for utilization in both traditional and new applications, such as coalbed demethanation. This paper presents the results of work in the Quinsam coalfield, which is part of the Comox sub-basin. There are two coal deposits of interest in the coalfield, Quinsam to the north and Chute Creek to the south.
The Quinsam and Chute Creek coal deposits occur in the Comox Formation, at the base of the Upper Cretaceous Nanaimo Group. The stratigraphy of the Comox Formation resembles that in adjoining areas, and three members are distinguished: in ascending order, Benson, Cumberland and Dunsmuir. Patterns of sedimentation, and hence of coal distribution, were controlled by the irregular topography of the pre-Cretaceous basement. Coal measures are generally only gently deformed by block faulting and tilting, with regional dips from 8 to 12 degrees to the northeast. Three sets of faults have been mapped in the study area.
Potentially mineable coal beds at Quinsam and Chute Creek lie at different positions in the stratigraphic section. In the Quinsam area these coals are close to basement, and occur in the Cumberland member. They are older than coals of the Chute Creek area, which lie near the top of the Comox Formation in the Dunsmuir member. Coal measures of the Cumberland member were probably deposited in back-swamps, while the Dunsmuir coals were formed in back-barrier lagoons.
The Quinsam coal can be correlated, with varying assurance, with coals in other parts of the Comox sub-basin. Given available data, the Chute Creek coals cannot be correlated with coal from outside the study area.
The Quinsam and Chute Creek coals straddle the boundary between high-volatile ‘A’ and ‘B’ bituminous rank. Mean-maximum vitrinite reflectance (Rmax) values range from 0.52 to 0.85 per cent. Averaged proximate analysis (air-dried, raw coals) range as follows: residual moisture, 1.8 to 4.0 per cent; ash, 7 to 38 per cent; volatile matter, 27 to 40 per cent; fixed carbon, 34 to 54 per cent; and sulphur, 0.5 to 4.2 per cent.
The Brinco Coal Corporation is currently conducting both open-pit and underground mining operations at the Quinsam mine-site. These coals average 26.5 megajoules per kilogram (11 400 British thermal units per pound), 0.8 per cent sulphur, 36 per cent volatiles and 48 per cent fixed carbon. Ash content ranges from 9 per cent in open-pit operations to 17 per cent in underground operations.
The current total coal resource estimate for the Quinsam property is 23.3 million tonnes of open pit reserves and 19.9 million tonnes of underground reserves, for a total of 43.2 million tonnes, of which 23.04 million tonnes are proven. The total in-situ coal resource within the Chute Creek ‘A’, ‘B’, ‘C’ and ’D’ coal beds, is 5.26 million tonnes; of this, 3.35 million tonnes are considered to be potentially mineable.
Preliminary calculations suggest a potential coalbed methane resource of 30.1 billion cubic metres or 0.09 trillion cubic feet in the Quinsam sub-basin. This deserves consideration both as a possible on-site energy source and as a potential safety hazard in underground mi n ing operations.
Much of the study area has been intensively drilled, and therefore is unlikely to contain undiscovered coal resources. The country lying east of Iron River and north of Woodhus Creek may contain additional resources in the Chute Creek coal zone and in the No.3 coal bed. The northern limit of mineable coal in the No.1 bed, down dip from Quinsam colliery, is unknown owing to lack of sufficiently deep drilling.
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