The Trefi coal property is located south of the Pine River Valley, approximately 30 kilometres southwest of Chetwynd in the Peace River District of northeast British Columbia.
The main coal-bearing unit at the property is in the Fort St. John Group in what was known as the Walton member or Member 4 (Bulletin 52) in the Lower Cretaceous Boulder Creek Formation. This consists of sandstone, siltstone, claystone, carbonaceous claystone, occasional conglomeratic sandstone and two main coal seams. This member overlies the upper conglomerate in the Boulder Creek Formation. The coal occurs towards the base of the member, which, in the south, varies from 60 to 88 metres thick, averaging 68 metres and, in the north, varies from 51 to 65 metres thick, averaging 54 metres.
Coal also occurs in the Lower Cretaceous Gates (Fort St. John Group) and Gething (Bullhead Group) formations, but these formations do not outcrop extensively and the coal occurs at depth.
The dominant structural feature on the property is the northwest trending Pine River anticline. This lies along the west margin of the property. The northeast limb dips 25 to 45 degrees northeast and shallows towards the Hulcross syncline. The latter is broad and narrows to the southeast, terminating north of Highhat Mountain. To the northeast, the Hulcross syncline is paired with the Commotion anticline which converges with the Pine River anticline to the north. Folds are broad with some localized faulting and all folds plunge southeast. South of Highhat Mountain the structure becomes more complex with fold amplitudes increasing and some thrusting taking place.
Two main seams are present but other thin seams also occur. All the seams show considerable lateral variation. The coal is thought to have been deposited in a high energy, inter-distributary, prograding deltaic environment which resulted in poor lateral seam continuity. Due to channel cut-outs and limited areas of deposition, seam characteristics vary considerably both vertically and laterally.
The extent of the Highhat seam (seam H) is limited, and it attains a marginal economic thickness north of the Highhat River only. It occurs at the base of the Walton member and lies either directly on the upper conglomeratic unit of the Boulder Creek member or within 1 metre of the contact. Its thickness ranges up to 2.68 metres, and its composition varies laterally.
The Caron seam (seam C; foremost economic seam on the property) varies in thickness from 2.7 to 0.18 metres, and exhibits very rapid lateral changes. It occurs within 11 to 19 metres of the base of the unit, and is the most laterally extensive of the Trefi seams (the 1.0-metre isopach ranges from north of the Highhat River to the southern extent of coal deposition on the property). The eastern edge is lobate in nature, indicating adjacent areas of thickening and thinning.
The Trefi property originally extended from the Highhat River in the southeast to north of the Pine River along the Pine River anticline. Seams north of the Pine were found to be thin and discontinuous and those claims were relinquished (Coal Assessment Report 681).
Gulf Canada Resources Inc. explored the Trefi property in the early 1980s, including 27 drillholes (6332 metres). Analyses of air dried raw coal from the Caron seam yielded the following data: ash, 7.78 to 28.46 per cent; volatile matter, 18.08 to 22.66 per cent; fixed carbon, 52.8 to 68.77 per cent; BTU per pound, 10,482 to 13,749; and sulphur, 0.32 to 0.38 per cent. Total inferred resources are 106,009,098 tonnes for the Caron seam and 16,530,800 for the Highhat seam (Coal Assessment Reports 680, 681).
In 2009, Trefi Coal Ltd. (a wholly owned subsidiary of Anglo Pacific Group Plc.) drilled five rotary holes (1006 metres) on the Trefi property in the Highhat River area. To allow for direct comparison with the historic data, two core samples were taken from seam C in drillholes near to the 1980s drillholes. Analysis of these samples indicate that the coal is medium volatile bituminous in rank, and a relatively low ash clean product (7.3 per cent) can be produced by washing at 1.60 Specific Gravity with reasonable product yield. The clean coal has low sulphur content (0.25 per cent) and a calorific value of 7855 kilocalories per kilogram on an air dried basis (Resource Estimate for the Trefi Coal Property, 2010).
Interpretation and modelling of the Caron seam (seam C) reports a resource estimate of 14.25 million tonnes Measured, 24.85 million tonnes Indicated, and 51.50 million tonnes Inferred of weak coking coal at the Trefi property (Resource Estimate for the Trefi Coal Property, 2010).