Work History
Staked as Tom cl 1-146 (60495) in Sep/51 by L. Seville and A. Lindsay for Hudson Bay Exploration and Development Company Ltd, which carried out geological mapping and hand trenching in 1951; drilled 37 holes (5435 m) from 1951-53; carried out geological mapping, geochemical sampling and magnetometer surveying in 1966; geochemical sampling and drilled 16 holes (3233 m) in 1968; carried out 1 809 m of drifting on the 1447.8 m (4750 foot) level, drilled 75 underground holes (3617 m), bulk sampling and metallurgical testing in 1970-71; geological mapping, geochemical sampling, EM and gravity surveying and bulldozer trenching from 1976-78; drilled 5 holes (587 m) in 1978 and drilled 15 holes (2295 m) in 1979. The claims were surveyed in 1953, leased in 1955 and renewed for a further 21 years in 1976.
Hudson Bay staked Tom cl 147-183 (YA45447) contiguously to the south in Aug/79 and carried out geological mapping, geochemical surveying in 1980 and 1981; magnetometer surveying and bulldozer trenching in 198l and 1983. The 1983 trenches, which failed to reach bedrock, were deepened in 1985. Hudson Bay also staked TS cl (YA42414) to the north in 1981 and explored with test pitting later in the year.
Between 1980 and 1982, Hudson Bay completed part of a major feasibility study which included 120 m of drifting to rehabilitate the adit portal, drilling of 12 surface holes (1457 m) and 18 underground holes (1 174 m), 923 m of decline, bulk sampling, engineering and environmental studies. Hudson Bay carried out minor trenching and a joint feasibility study with Aberford Resources Ltd on this and the adjoining Jason deposit (Minfile Occurrence #105O 019) in 1985.
Fringe staking included Star cl (Yl7754) to the east in Jun/67 by Spartan Exploration Ltd. This was restaked as Cree and Sioux cl (YA216) in Jul/76 by Welcome North Mines Ltd, which later entered a joint venture with Canico (Inco). Inco carried out geological mapping and a magnetometer surveying in 1977, before dropping the option in 1978. Yumac Syndicate (Giant Yellowknife Mines Ltd, Canada Southern Petroleum Ltd, Nemco Exploration Ltd and Highland Resources) tied on the Argo cl (YA6365) to the north in Aug/76 and ccarried out geological mapping and geochemical sampling in 1977 and 1978. In 1980, Welcome North optioned its claims to Charlotte Resources Ltd.
Cominco optioned the property in Jul/88 and staked Tome cl 1-192 (YB14942) to the east in Aug/88, Jerry cl 1-26 (YB15501) in Oct/88 to the south, Mac cl 1-12 (YBI2862) in Oct/88 to the north and carried out contour geochemical sampling of the Tome claims that year. Cominco remapped the property and began a program of surface drilling to test for extensions of the West and Southeast zones at depth. This program included 4 holes (2226 m) in 1988, 4 holes (2175 m) in 1989, 7 holes (3578 m) in 1990 and 8 holes (2882.7 m) in 1991. The 1991 holes tested peripheral geochemical and geological targets. More Jerry claims were added (YB33233) in Jul/90 and explored with contour soil sampling in 1991. Cominco dropped its option in Aug/92. See Work History table for more recent work.
Capsule Geology
The Tom stratibound lead-zinc deposits consist of galena, sphalerite and barite in fine-grained black clastic rocks of the Devono-Mississippian Earn Group. Mineralization occurs in three zones: Tom West (this MINFILE), Tom East (MINFILE pending) and Tom Southeast (MINFILE pending).
All mineralization at the Tom property occurs at or near the contact between conglomeratic submarine fan deposits (Macmillan Pass Member) and overlying blue-grey weathering carbonaceous cherty mudstone and radiolarian chert (Tom Sequence). The mineralization varies from well laminated and stratiform to brecciated stockwork adjacent to the Tom normal fault. Tom West and Tom East (MINFILE pending) are thought to have been a continuous lens prior to deformation of the Tom Sequence. The host rocks are believed to have been deposited in narrow grabens during Devonian rifting of the Cordilleran passive margin. The Tom deposits are confined to a small basin outlined by the outcrop pattern of chert-pebble conglomerates of the Macmillan Pass member and a thickened isopach of the Tom Sequence rocks.
Detailed mapping by Cominco has showed that the West zone and Southeast zone deposits occupy two separate troughs flanking a narrow horst block formed of chert pebble conglomerate. Flanking sediments wedge out against the horst block and substantial differences in stratigraphy exist between the two troughs.
The horst block separating the Tom West and Southeast zones coincides with a tightly folded north-south doubly-plunging anticline ('Tom anticline'). Detailed structural analysis by McClay (1983) revealed three phases of folding and faulting. The Tom anticline is a first phase structure which has been refolded by open second phase structures with east-west axes. Second phase folds are associated with low-angle thrust faults and have a well developed axial planar slaty cleavage. Third phase structures are open north-south folds which fold the second phase slaty cleavage. The deformation is related to folding and thrust faulting during the Late Jurassic and Early Cretaceous.
The Tom West zone is a tabular body 1000 m long and up to 40 m thick which dips 60 degrees southwest. It extends downdip for 360 m and is terminated at its south end by a brecciated vent complex. Metal zoning restricts economic mineralization to within 300 m of the vent, based on a 10% Zn + Pb cutoff. Four distinct ore facies are recognized in sequence away from the vent:
(1) The Vent facies consists of network pyrite-pyrrhotite-galena-sphalerite-ankerite-siderite-quartz veins with variable chalcopyrite, arsenopyrite and tetrahedrite. Brecciated sulphide textures and replacement of sedimentary barite, sphalerite and galena by pyrrhotite, pyrite and iron carbonate are characteristic, and grades of 15-30% Pb+Zn and 150-200 g/t Ag are common in the upper part. The lower parts are high in iron sulphides and siderite with 2-5% combined Pb-Zn.
(2) The Pink facies consists of interbedded barite, chert, cream coloured sphalerite, fine grained pyrite and black barium carbonate, silicified and overprinted by recrystallized multi-coloured sphalerite and coarse-grained galena and iron carbonate. Grades of 10-30% Pb+Zn are common in this facies.
(3) The Grey facies forms the largest part of the Tom West zone and consists of interbedded sphalerite, fine grained galena, pyrite, light grey chert, and abundant barite, barium carbonate and barium feldspar. The high barium content has diluted the lead and zinc grades, which typically run 0-2% lead, 4-5% zinc and negligible silver. The light grey colour reflects bleaching of organic matter from the chert.
(4) The Black facies consists of black chert and mudstone with fine laminae of sphalerite, galena, pyrite and barite-witherite. Grades are as low as 4-10% Zn+Pb in this zone, except for the upper few metres which grade low in silver and lead but contain 7-12% Zn and were included in Hudson Bay's ore calculations. The contact between the black facies rocks and the enclosing sediments is gradational, and pyrite and minor sphalerite and barite laminae extend hundreds of metres into the overlying chert and mudstone.
The Tom East zone consists of a series of contorted fault-bounded pods of high grade laminated barite, chert, sphalerite and galena, near the hinge of the Tom anticline. Grades are approximately 22% Zn+Pb, and 165 g/t Ag.
The Tom Southeast zone is thinner and higher grade than most of the west zone. It consists of a tabular body 400 m long and 0.5 to 6 m thick which dips 60-70 degrees east. The zone extends downdip for at least 350 m. Mineralization consists of finely laminated sphalerite, galena, pyrite and black cherty mudstone, with a much lower barium content than the west and east zones. Grades are approximately 8-13% Pb, 8-12% Zn and up to 277.7 g/t Ag. Barite content ranges from 0.6% at the south end close to the vent to 3.0% further north.
Geochemical studies of the West zone deposit have shown that copper, lead, silver, antimony and arsenic are concentrated in the Vent facies, zinc and mercury are most abundant in the Pink facies, and barium is enriched in the Pink and Grey facies. Lead and strontium isotope ratios indicate that the metals are derived from a radiogenic crustal source, probably the Canadian Shield to the east. Fluid inclusions in quartz and siderite yield homogenization temperatures in the range 157 to 335°C, and an average salinity of 9.1 wt-% NaCl equivalent. Primary depositional and early diagenetic textures are well preserved.
Trenching and hand pitting on the Tom South and TS claims in 1980 encountered only barren Upper Devonian stratigraphy. Canico discovered baritic, but otherwise barren, Upper Devonian shale horizons on the Cree and Sioux claims. Minor disseminated galena, sphalerite and stibnite were also discovered in a granodiorite dyke cutting Devonian strata on the southern part of the Sioux claims.
