The Discovery occurrence comprises the Lower Discovery Creek, Upper Discovery Creek, Evans Creek and Davis Creek coal seams. The discovery outcrop lies 4 kilometres west-northwest of the junction between Currier Creek and the Skeena River, about 147 kilometres northeast of Stewart.
The occurrence forms part of the southeast Groundhog coalfield, an oblong (roughly 30 by 80 kilometres) area extending southeast from the headwaters of the Klappan and Little Klappan rivers to Groundhog Mountain. Exploration history of the coal prospects of the southern Groundhog coalfield is detailed in Coal Assessment Reports 100, 838, 931, 956, 980, and Tveten (2007), and Morris and Engler (2010).
The anthracite deposits at the Discovery prospects are part of the southern Groundhog coalfield near the north end of the Bowser Basin of British Columbia. The Bowser Basin was filled with sediments deposited from eroding mountains during the late Jurassic and early Cretaceous. At the northern end of the basin, peat formation occurred in deltaic environments. These peat bogs were metamorphosed to form the coal-bearing sequences of the Groundhog coalfield, an oblong (30 by 80 kilometres) area extending southeastwards from the headwaters of the Klappan and Little Klappan rivers to Groundhog Mountain in the Skeena Ranges, an area characterized by mountainous terrain with broad valleys.
The coal-bearing sequences of the Groundhog coalfield reach approximately 1100 metres in thickness, with 33 identified coal horizons of up to 11.8 metres in true thickness interbedded with primarily mudstone, siltstone and sandstone. The coal-bearing units and surrounding beds were later deformed by compression that created open to tight folds that are near vertical to overturned to the northeast. Fold axes strike 30 to 60 degrees to the northwest and axial planes dip 25 to 85 degrees southwest. The folds are cut by thrust faults striking 020 to 040 degrees to the northeast and dipping 10 to 25 degrees southwest. The whole area is cut by younger high-angle faults trending northwest, north and northeast.
MacLeod and Hills (Canadian Journal of Earth Sciences 1990) proposed that sedimentation was continuous and derived from the northern Cache Creek Terrane. Five formations have been defined comprising the fully marine Ashman and coeval Mt. Jackson formations, the alternating marine and fluvial Currier Formation, the dominantly fluvial McEvoy Formation and the fully fluvial and alluvial Devil's Claw Formation. Formation contacts are gradational and established by the predominance of rock type, ranging from mostly shale in the upper Ashman to mostly conglomerate in the upper Devil's Claw.
Two phases of post-sedimentary deformation and the lack of marker horizons complicate correlation of beds from location to location in the Groundhog coalfield. Phase 1 deformation resulting from a northeast-southwest compression produced a major northwest-trending synclinorium with associated lesser folds and thrust faults. Phase 2 deformation generated open folds having a northeast orientation. Deformation is most intense in the less competent, coal-bearing sequences.
Three stratigraphic intervals of good coal development have been defined (Fieldwork 1989, 1990). The oldest and thickest seams (10 metre seams have been reported but are likely tectonically thickened) are found in the dominantly shale and sandstone beds of the Currier Formation and are generally of anthracite to meta-anthracite grade. Upwards of 25 individual seams have been documented (MacLeod and Hills, Canadian Journal of Earth Sciences 1990). The fossil assemblage found in the Currier Formation indicates sedimentation occurred from the Upper Tithonian (148 Ma) to Upper Hauterivian (124 Ma). Pervasive marine influence suggests the deposits accumulated in the subaqueous delta and lower delta plain. Coal seams in the McEvoy Formation are generally thinner (rarely exceeding 1 metre) and of subanthracite to anthracite rank. The greater proportion of siltstone, sandstone and conglomerate in the McEvoy Formation indicates a dominantly fluvial delta system wherein deposits accumulated in interchannel paralic marine or brackish water environments. Thin seams of high-volatile bituminous coal have been encountered amongst the dominantly fluvial sandstone and conglomerate beds of the Lower to Upper Cretaceous Sustut Group which unconformably overlies the eastern margin of the Bowser Basin.
The nomenclature of the coal-bearing rock units in the Groundhog area has a complex history. It has been variously referred to as the Currier Formation (Bustin and Moffat, Canadian Society of Petroleum Geologists Bulletin 1983; Macleod and Hills, Canadian Journal of Earth Sciences 1990, and most industry Coal Assessment Reports), the Groundhog-Gunanoot facies (Eisbacher, Geological Survey of Canada Paper 73-33), the Gunanoot Assemblage (Richards and Gilchrist, Geological Survey of Canada Paper 79-1B), and the Groundhog-Gunanoot Assemblage (Evenchick and Thorkelson, Geological Survey of Canada Bulletin 577, 2005). Evenchick and Thorkelson (Geological Survey of Canada Bulletin 577) provide a history of stratigraphic nomenclature in the coalfield, and a discussion of the debate over the age of the coal-bearing unit, which they refer to as the Groundhog-Gunanoot assemblage. The age is not well-constrained, and may vary by area; however, it is mainly between latest Jurassic and late Early Cretaceous.
The Lower Discovery Creek coal seams were the first major discovery in the Groundhog coalfield. The first claims were staked in 1903. Skeena Coal Company and the British Columbia Anthracite Syndicate conducted prospecting and sampling followed by description and analysis of the Pelletier, Benoit, Garneau, Ross, Scott and Middle, Lower and Upper Anthracite seams in 1910 to 1912 (Coal Assessment Report 838). G.S. Malloch of the Geological Survey of Canada visited Groundhog coalfields in 1912 (reported in Geological Survey of Canada Memoir 69). In 1948, Buckham and Latour (Geological Survey of Canada Bulletin 16) conducted a mapping and data collection program of the Groundhog coalfield wherein they documented 192 coal showings.
Between 1970 and 1981, many companies, including Coastal Coal, Placer, Quintana, BC Hydro, Petrofina, Groundhog Coal, PetroCanada, Suncor, Procan Resources and Imperial Metals explored the Discovery and adjacent coal prospects in the southern Groundhog coalfield. The majority of exploration over those years was field mapping of coal outcrops and trenching, with some drilling.
Assessment of the Groundhog coalfield potential by a consortium of companies in 1970 estimated upwards of 3.6 billion tonnes of speculative coal reserves in the southeastern Groundhog coalfield (Coal Assessment Report 98). Testing of samples from trenches and drill core, for seams exceeding a 0.5 metre thickness, gave the following results:
--------------------------------------------Fixed Carbon 82.4 per cent Ash Content 9.8 per cent Volatile Matter 7.2 per cent Sulphur Content .6 per cent Calorific Value 7,414 calories per gram -------------------------------------------- |
The above results are based on washed samples using a specific gravity of 1.75 grams per cubic centimetre; float yield was 38.8 per cent.
Drilling of the Lower and Upper Discovery Creek seams has defined 12 seams totalling 10.8 metres and 9 seams totalling 8.3 metres, respectively. There are 42 million and 11 million tonnes of inferred coal reserves in the Lower and Upper Discovery Creek seams, respectively, accessible by open pit. An additional 290 million tonnes, amenable to underground mining, occurs in the gently dipping strata between Discovery and Evans Creek (Coal Assessment Report 98). Testing of the most prominent seams gave the following results:
---------------------------------------------------------------------- Lower Discovery Upper Discovery Creek Seams Creek Seam Float yield 23.7 38.9 58.3 Seam thickness 2.0 1.5 1.9 Fixed carbon 75.3 80.7 84.9 Ash content 17.1 13.1 9.4 Volatile matter 7.6 6.2 5.7 Sulphur content 1.0 0.8 0.4 Calorific value 6,652 7,025 7,529 ---------------------------------------------------------------------- |
Thickness is in metres; calorific value is in calories per gram; all other values are in per cent. The float yield is based on a specific gravity of 1.75 grams per cubic centimetre. Coal rank is anthracite to subanthracite based on fixed carbon to volatile ratios (Coal Assessment Report 98).
In the mid-1980s, Suncor was active at Mount Jackson (104A 083), and Gulf Canada did work at the Panorama (104A 085) and Discovery prospects. In 1988, Gulf conducted trenching, measuring of sections, mapping and sampling at Mount Jackson.
West Hawk Development Corp. of Englewood California optioned property at the Discovery prospect from 2006 to 2011 and drilled 11 holes totalling 2051 metres in 2008.
In 2010, Anglo-Pacific and its subsidiary Panorama Coal released a National Instrument (NI) 43-101 compliant Resource Estimate for their portion of the surface mineable properties in the Discovery and Panorama prospects at 13.7 million tonnes Indicated and 24.1 million tonnes Inferred. Coal is of semi-anthracite to anthracite rank. A property-wide further 70 million tonnes in the speculative class was estimated (Morris and Engler, 2010).
Atrum Coal of Australia acquired tenure over parts of the Discovery, Beirnes-Anthracite (104A 086), Mount Jackson (104A 083) and Telfer (104A 087) prospect areas in 2011. They drilled 15 diamond-drill holes in the summer of 2012, and 64 drillholes in 2013 on the Discovery prospect. A pre-feasibility study (PFS) was completed in 2014, along with drilling of 41 exploration holes, 10 hydrogeological holes, and a geophysical (seismic) survey. Additionally, Atrum announced completion of Phase 1 portal drilling perpendicular to the main seam #70, and the mining of a bulk sample and delivery to the Stewart Bulk Terminal. Atrum Coal reports a JORC compliant resource estimate of 16 million tonnes measured, 553 million tonnes indicated, and 998 million tonnes inferred (Atrum Coal Annual Report 2014).
In 2016, Atrum Coal NL received a permit for a 100,000-tonne bulk sample extraction at its Groundhog anthracite project. The company revised its prefeasibility study this year and proposes a staged mining plan, beginning with an underground mine at Groundhog North. The proposed Phase 1 operation would initially produce 880,000 tonnes per year,ramping up to 1.6 million tonnes per year at maximum capacity. Environmental baseline work continues in preparation for entering the Environment Assessment process. Atrum Coal NL, in a Joint Venture with JOGMEC (Japan Oil,Gas and Metals National Corporation), also drilled at their Panorama North project (104A 085), about 20 kilometres west of the Groundhog project.
In 2017 at the Groundhog North project, Atrum Coal Ltd. continued environmental baseline studies and extracted anthracite samples for testing in North Asian steel mills. A bulk sample permit application was put on hold. Atrum’s Panorama project (104A 085) was drilled and sampled for washability testing.
The massive Groundhog project (100 per cent Atrum) has been the subject of multi-decade historical exploration work and contains an existing JORC Resource estimate of over 1 billion tonnes (156 million tonnes Measured, 453million tonnest Indicated and 407 million tonnes Inferred). These resources are comprised of premium, high-grade anthracite with low product ash (Atrum Coal Annual Report for year ended December 31, 2019.
