Summary:
The Murray River property is located within the Peace River Coalfield (PRC) in the eastern foothills of the Canadian Rocky Mountains of northeastern BC. The western margin of the Foothills Belt is classified as the easternmost major thrust fault that emplaced Paleozoic strata over Mesozoic strata. The eastern margin is a series of echelon thrust faults that separate the Foothills from the gently dipping strata of the Alberta Plateau (Holland 1976). The Foothills Belt is characterized by folded and faulted Mesozoic sediments. The deformation within the Foothills Belt is variable – mostly decreasing in complexity toward the eastern margin. Deformation within the Rocky Mountains involves complicated folding and faulting. Regional axes for folding and faulting trend northwest, dipping to the southeast. In the Foothills Belt, dips tend to be 20° or less with local folds and undulations significantly modifying this value.
In the PRC there are two main coal-bearing units: the Gates Formation and the Gething Formation (British Columbia Geological Survey n.d.). Both Lower Cretaceous units were subjected to varying degrees of burial prior to the Laramide deformation and mountain-building episodes that took place approximately 40 to 70 million years ago when the Pacific and North American plates collided. The Laramide Orogeny increased the overall maturity of the coal seams. Based on drill core information from the neighbouring Quintette mine (immediately adjacent north of the Murray River Forest Service Road), coal seams of the Gates Formation can be comprised of up to 10 separate seams and the average cumulative thickness of the coal seams is as high as 17 metres.
In general, the coal seams within the proposed mining area have moderate structural conditions. The seams dip to the northeast and at more than 30° in the flanks of the fold in the west of the region. The coal seams with mining value occur in the Gates and Gething formations. There are nine coal seams developed in the Gates Formation, which are labeled alphabetically from top to bottom (A to K). There are also seven coal seams developed in the Gething Formation (from top to the bottom: Superior, Trojan, Lower Trojan, Titan, Falls, Little Mogul, and Mogul). The F and J seams are the major workable coal seams of this area, with other seams providing locally mineable sources.
Seven main coal seams (B, C, D, E, F, G/I, and J) were identified during exploration (Appendix 3&A). The main workable coal seams of the mine are seams D, E, F, G/I, and J. Seams D and E are thin or moderately&thick, F and J are moderately thick, whereas G/I is very thin and therefore not targeted. The total distance between the coal seams is 80 to 120 m. In order to achieve the mine’s production capacity, seams F and J are designed as the main mining seams, and seams D and E are the auxiliary mining seams.
Coal Seam D
Seam D is the first workable seam. The roof rock is generally mudstones overlain by conglomerate. The seam is continuous with good quality coal, but the coal thickness can vary significantly from tens of centimetres to more than 5 m. The average thickness is 2.12 m.
Coal Seam E
Seam E is located 15 to 30 m below seam D. The interburden between seams D and E is siltstones and fine,grained sandstones. Seam E thickness ranges from several centimetres to 8 m, with an average thickness of 2.32 m.
Coal Seam F
Seam F lies about 20 m beneath seam E. It is a continuous, thick coal seam of good quality. There are most likely multiple,layer sub,seams within this seam. The thickness is between 0.67 m and 7.07 m with an average of 3.46 m.
Coal Seam G/I
The G and I seams are typically referred to as the G/I seam, as the two seams are often coalesced. This seam is continuous, stable and partly workable at a variety of thickness from 0.40 m to 3.52 m. The average thickness of this seam is 1.60 m.
Coal Seam J
Seam J is 20 m underneath Seam G/I. It is also the thickest and most widely distributed seam. The thickness is from 2.60 m to 9.20 m with an average of 6.19 m.