The Driftpile Creek developed prospect is based on stratiform barite-lead-zinc mineralization and is situated near the headwaters of Driftpile Creek near the western edge of the Muskwa Ranges, approximately 22 kilometres northeast of the Northern Rocky Mountain Trench (Assessment Report 7658).
The deposit is in the Gataga mineral district, in a belt of Paleozoic basinal-facies sedimentary strata known as the Kechika Trough, the southeastern arm of the Selwyn Basin (Exploration and Mining Geology, Volume 1, page 1). These rocks belong to Ancestral North America (Geological Survey of Canada Map 1713A). The Gataga mineral deposits are characterized by stratiform sedimentary exhalative barite-sulphide mineralization, which occurs at certain Ordovician, Silurian and Devonian stratigraphic horizons. The last, represented by the Driftpile Creek deposit among others, are the most economically significant. They are believed to have formed during sedimentation, from metal-enriched brines released into fault-controlled, starved sub-basins that developed during rifting of the ancient continental margin.
The area around the Driftpile Creek deposit is underlain mainly by the Middle to Upper Devonian Gunsteel Formation (informal name) of the Devonian-Mississippian Earn Group (Geological Survey of Canada Memoir 373, Map 1343A). This unit is preserved in a broad, northwest-trending, tightly folded synclinorium disrupted by moderately-dipping, northeast-verging thrust faults. Fold axes plunge 10 to 20 degrees to the northwest. Bedding, cleavage and fold axial planes generally strike approximately 325 degrees and dip moderately to steeply southwest, though there may be northeastward dips due to the folding. To the southwest of the immediate area, rocks of the underlying Ordovician to Lower Devonian Road River Group are exposed in the hangingwall of the Mount Waldemar thrust fault (informal name).
The Driftpile mineralization was discovered in 1973 following a 1970 regional geochemical reconnaissance survey (Assessment Report 5359). A number of limonitic gossans, ferricrete and 'kill zones' are present on the property but unaltered mineralization is uncommon on the surface, so subsequent exploration has concentrated on detailed geological mapping and soil sampling, and close to 20,000 metres of diamond drilling.
Mineralization is restricted to the Gunsteel Formation (the same unit that hosts lead-zinc-silver mineralization at the Stronsay or Cirque deposit, 80 kilometres to the southeast). Conodonts extracted from carbonate rocks at Driftpile Creek indicate that the age of the mineralization is mid-Fammenian (Late Devonian; Insley 1990).
The Gunsteel Formation mostly comprises blue-grey weathering, carbonaceous black shale and silty mudstone, cherty argillite and radiolarian chert. Within this dominantly mudstone-shale stratigraphy are a number of horizons of siliceous shale or cherty argillite, which are enriched with barite and/or pyrite. Barite is in the form of nodules, disseminations, intercalated thin laminae, or massive, centimetre-scale beds. Pyrite is generally present as laminations in mudstone, or may be associated with barite, or with carbonate concretions.
Locally, at least seven zones of mineralization have been identified along a north-northwest trend over an area of approximately 5 by 2 kilometres along.
Although their stratigraphic relationships are uncertain because of the structural complexity, at least two different sulphide-rich zones, referred to as the ‘Upper’ (North Trench zone) and ‘Lower’ (Main zone) have been distinguished by detailed mapping and diamond drilling (Assessment Report 23109; Insley (1990); Fieldwork 1994). The Main zone is primarily a sulphide-carbonate facies; visible barite is uncommon. The zone consists of 35 to 80 per cent sulphide in a carbonate matrix, separated or 'diluted' by intervals of black graphitic shale or mudstone. Most of the sulphide is fine-grained, finely laminated or framboidal pyrite, associated with irregular bands and concretions of calcite. The pyrite grains may be graded or show soft-sediment deformation. Sphalerite and galena may be present with the pyrite, but they are particularly well developed in some places in a layer of fine-grained massive sulphide near the base of the zone, as irregular masses or discrete bands. The estimated true thickness of the Main zone is between 20 and 70 metres (Fieldwork 1994); Insley (1990) expressed the thickness in terms of two 3- to 36-metre-thick subunits. Overall, it carries 1 to 2 per cent zinc (Assessment Report 23109).
The best mineralization exposed at surface on the property is reported to be exposed in trenches, located approximately 1400 metres north of the Driftpile Creek Lower (Main) zone in the North Trench zone, where thin parallel bands of discrete, irregular galena and sphalerite occur in dark grey bedded barite (Assessment Report 7658, Figure 4a). Later work describes the Upper (North Trench?) zone, located 100 to 200 metres higher in the formation than the Lower (Main) zone, to be comprised of barite-sulphide mineralization, in siliceous or non-siliceous mudstone with pyritic laminations. Barite occurs in massive beds or laminations, or in nodules. Pyrite is subordinate to barite, but may form massive layers, locally accompanied by strong sphalerite and galena. There are few carbonate concretions here. According to Insley (1990), this Upper zone occurs in four 2- to 20-metre-thick units.
Drilling on the Camp zone, located several hundred metres downstream to the northwest of the Main zone, has determined that mineralization is present in the keel of a syncline, trending across a ridge top. The mineralized horizon has been largely eroded, limiting tonnage potential.
Strong pyritic mineralization with discrete sphalerite/galena laminations was intersected on the Ridge zone, located approximately 2.5 kilometres southeast of the Main zone. Thrust faulting has displaced the mineralized horizon such that it has been subsequently eroded along strike. This zone is located immediately southwest of the DR (MINFILE 094K 077) occurrence and may encompass it.
Geological mapping in the Canyon zone, located approximately 2.2 kilometres north-northwest of the Main zone, indicated potential for a second mineralized horizon at depth. Subsequent drilling confirmed the presence of a single horizon, repeated by thrusting. All mineralization is baritic and distal.
Drilling on the East zone, located approximately 1 kilometre east of the Main zone, has identified a mineralized horizon consisting of barite and sulphide. The horizon was tested in three places over a 1-kilometre strike length.
The South zone is located approximately 1.5 kilometres south of the Main zone and comprises a tight to isoclinally folded sequence of hangingwall turbidites, a mineralized horizon (40 to 60 per cent pyrite with sphalerite) and overturned hangingwall turbidites. Continued drilling demonstrated that the mineralization thinned and weakened along strike and downdip.
In 1980, it was reported that shallow drilling in 11 areas indicated reserves of approximately 18,145,000 tonnes averaging 2.38 per cent combined lead-zinc (Canadian Mines Handbook 1980-81, pages 280-281).
In 1994, a qualitative and preliminary estimate of the geological resource in the lower mineralized subunit of the Main zone was given as 2,440,000 tonnes averaging 11.9 per cent zinc and 3.1 per cent lead, with a cut-off grade of 8 per cent zinc (Fieldwork 1994, page 263).
Work History
The Driftpile Creek occurrence was discovered in 1970 as the result of a reconnaissance stream sediment geochemical survey performed by Geophoto Consultants Ltd. During 1973 and 1975, Canex Placer Ltd. completed programs of geological mapping, geochemical (rock and soil) sampling, trenching and 15.0 line-kilometres of ground magnetic and electromagnetic surveys on the area as the D, P, G and Goof claims of the Driftpile property. During 1977 through 1981, Welcome North Mines Ltd., later in conjunction with Placer Development Ltd., completed programs of geological mapping, geochemical (rock, soil and water) sampling, trenching, at least 36 diamond drill holes, totalling 4796.2 metres, and a 3.6 line-kilometre ground electromagnetic survey on the area as part of the Goof, Knot, P, Bob, Pig, Saint and Sol claims of the Gataga Joint Venture property. In 1978, the best drill intersection from the North Trench zone (hole 78-07) was 11.7 metres grading 7.45 per cent combined lead and zinc, whereas drilling on the Ridge zone yielded 3 per cent combined lead and zinc over 26.2 metres and 4.14 per cent zinc over 7.5 metres in drillhole 78-09 (Assessment Report 7149 and 24609).
In 1993, Teck Corp. completed 13 diamond drill holes, including four drillholes totalling 1325.3 metres, on the Driftpile Creek property. Drilling confirmed that high-grade mineralization in the Main zone extends downdip for at least 100 metres, although drilling failed to intersect mineralization farther south along strike, indicating that it weakens in that direction. Previous work has demonstrated that mineralization in the Driftpile Creek area has a strike length of between 2 and 3 kilometres and a surface width of 1.5 kilometres (Assessment Report 7658; Fieldwork 1994). Other favourable zones in the area are known as the Camp, East, North Trench, South and Canyon zones (Fieldwork 1994). In 1993, drilling on the Main zone intersected a 12-metre zone grading 10 per cent zinc and 1 per cent lead, including a zone of 6.02 metres grading 12.26 per cent zinc and 1.36 per cent lead in hole 93-56 (Assessment Report 23109).
In 1994, Teck Corp. completed a further 26 diamond drill holes, totalling 4817 metres, on the Driftpile Creek property. The program was undertaken to test areas of known mineralization on the property, other than the Main zone, tested in 1993. A total of five target areas, termed the Camp, South, Ridge, East and Canyon zones, were tested during the 1994 program. Several narrow high-grade intercepts of were obtained from the East zone, including 17.5 per cent zinc over 1 metre and 7.93 per cent zinc over 2 metres from hole 94-88, and 10.4 per cent zinc over 1 metre from hole 94-89, located 800 metres to the south (Assessment Reports 23561 and 24609). Locally, tight to isoclinal folding has thickened the mineralized horizon by up to five times. At this time, the horizon has not been tested for 800 metres between sections drilled in 1994 and has not been tested north of the northernmost section drilled in 1994. Also at this time, drilling on the South and Ridge zones yielded up to 3.01 per cent zinc over 36.28 metres in hole 94-73 and 3.85 per cent zinc over 12.79 metres in hole 94-78 (Assessment Reports 23561 and 24609).
In 2014, Teck Resources Ltd. completed a 222.4 line-kilometre airborne magnetic and electromagnetic (VTEM) survey on the Driftpile Creek property. In 2016, Teck completed a minor program of rock sampling and geological mapping on the area. Portable X-ray fluorescence analysis of samples (2686427, 266409 and 2686405) from the North Trench, Main and Ridge zones yielded values up to 0.55, 2.91 and 4.00 per cent zinc with 18.45, 0.07 and 0.50 per cent lead, respectively (Assessment Report 36309).
