Ore reserves taken in 1985 within the Tom Adit had been calculated at 13,385,400 tonnes, grading 6.53% Zn, 28.5 gr per ton, Ag, and 3.16% Pb in the West Zone. East Zone - 2,337,100 tons, grading 9.67% Zn, 167.3 grams per ton Ag, and 12.8% Pb.
Mine or Prospect Status: Abandoned
Type of workings: Underground Mine Workings
Township Location: Macmillan Pass
Closest City or Town: Yukon
Province and Country Northwest Territories, Canada
District location: Watson Lake Mining District
Subprovince: Watson Lake Mining District
Belt: Stratibound Deposition Area.
Tectonic Assemblage: Tom Sequence-Tom Anticline
Formation type: Mafic
Chemical Compositions: Quartz- Diorite, Brecciated, Cherty Mudstone, Conglomerate
Production: Negative-Exploration Only.
Common names: Tom Deposit- Tom Adit.
Lot, Concession, N/A - Claim 60595
Deposit Status: Past Producing
Primary Commodities: Pb-Zn-Ag
Secondary Commodities: Cu, Sio2, Au,
Geological Events: Stratibound Deposition
Start Date: 1951
Close Date: 1991
Re-Open Date: N/A
History of Development and Explorations
The Tom Adit Property was first staked in 1951, by L. Saville and A. Lindsley for Hudson Bay Exploration and Development Company, Limited. These foremost claims became known as the Tom Cl 1-146, before changing to 60495 as technology progressed. A diamond drilling program was set in place from 1951, to 1953, which was aimed at determining the grades within the Tom Adit Property. Diamond drilling that was taken place at the time had resulted in completing in 37 surface hole, totalling 5,436 m in length. It was reported that this discovery was made while following a sulfide mineralization of glacial boulders in Tom Creek which led to the surface showing.
Not much at the time was done on this property till about 1966, when important discoveries were made by Anvil Mining Corporation at the Faro Pb-Zn-Ag Mine Site. It was at this time when Development had renewed at the Tom Adit Location as it was named after the main creek which contributed to sulphide discoveries. Exploratory work was carried out when soil sampling and stream geochemistry was undertaken on this deposit zone. Diamond drilling from the surface was mainly done at a rather slow progress when 1 hole had only amounted to 10 feet of drilling. As explorations progress, it was by the end of 1967, when an ore-reserve calculation was made within the outcropping of the Tom Adit Zone. Ore Reserves at the time had proven that the Tom Adit was worthy in developing and a development proposal was made in 1970. This also resulted in sampling collecting over an area of 800 feet. Soil sampling had also resulted in negative results in which a geochemistry rock program was undertaken. This foremost program would end up resulting encouraging values that were obtained from rich mineralization areas on the Tom Adit Property.
It was in 1969, when the Fringe Claim had been staked as Star cl which is now registered as claim YI7714, and adjoins the Tom Deposit to the west. The staking at the time was mainly in control by company known as Spartan Exploration, Limited.
By 1971, development was shortly after progressing as it was during this time period when 315 feet of adit development was completed. Exploration work was also completed from the underground workings when 10 feet of diamond drilling was done in order to test the depth of the west zone. In 1971, the proven tonnage within the Tom Adit was calculated at 8.6 x 10 with an estimate grade of 2.75 ounces of Ag, 8.4% Zn, and 8.1% Pb. An additional ore reserve calculation was made when 10,000,000 tonnes of ore grading 0.7 ounces Ag per ton, 4.6% Zn, and 0.9% Pb.
Its also on surface that the West Zone which was being explored had been rich in Zn and Pb to encourage a development program. It was also reported that the west zone was also classified as typical stratiformed deposit of pyrite, sphalerite, and galena. Much of the geology was so much similar to the deposit which was uncovered within the Faro Pb-Zn-Ag Mine site. All sulphides which are present within the west zone are also parallel to bedding of galena and sphalerite which replace limestone. Projections on the West Zone had also reported this ore-body to have a strike length of 3,800 feet and various in width from 2 to 176 feet. Another zone was also encountered within the Tom Adit workings as the East Zone was reported as a massive Pb-Zn ore-body that may have occurred along a faulted section. It was also in 1972, when recent ore-reserves were given which the Tom Adit contained two zones that amounted in 9,000,000 tonnes grading 9.4% Zn, 8.1% Pb, and 2.75 ounces per ton in silver. The East Mine Zone was also considered to have varied in size as it range between 10 to 60 feet wide on the ore-body being explored.
During 1976, Yumac Syndicate, along with Giant Yellowknife Mines, Limited, Northern Southern Petroluem, Limited, Nemco Exploration, Limited, and Highland Resources were tied on the Argo Cl, which is now known as claim YB15501. The Argo Cl claim was rather situated to the north of the Fringe Claims that were owned by Welcome North Mines, Limited. Explorations on the claims were carried out in 1977, which resulted in completing geological mapping, and geochemical sampling.
The Fringe Claim was later renamed to the Sioux and Cree Cl, that is now commonly registered as YA216 in 1976. The claims were mainly picked up by Welcome North Mines, Limited who carried out an exploration program to the west of the Tom Deposit It was at a later time period when this company had entered into a join venture with Canico, which was a subsidiary company of (INCO). For the most part, this program had included geological mapping, and a magnetometer survey that was completed in 1977, before dropping the option by 1978.
There are two zones within the Tom Adit Property which are known commonly as the East Zone which is on the limb of the anticline and the West Zone is on the west limb. Anticline is known for plunging south 0.70 degrees to 0 degrees as it flattens at depth within the Tom Adit Workings. Limestone within the West Zone is also known for grading laterally to the north and south into grey chert. Reports on the structural geology had also indicated that the whole entire property was cut by a northeast trending faults. The Tom Deposit is also commonly known to be made up of graphitic argillites, black cherts, limestone, and pebbled conglomerates, which are apart of the Black Clastic Unit of Templeman Kluit, that's probably apart of Earn Group of Campbell. Pebble conglomerates are also known for being slightly mineralized which yield a precentage of 2% Cu.
Encouraging results from the Tom Adit Zone had shortly led to further development that was undertaken on this Adit. The adit was mainly driven within the outcropping for a distance of 315 feet which resulted in testing the continuation of the deposit by diamond drilling. A massive development program was shortly after undertaken in order to explore the West and East Zones of the Tom Adit Pb-Zn-Ag Mine Site. This decision at the time had resulted in driving the adit down to the 1,447.8 m level in order to explore the rich Pb-Zn-Ag mineralization. Diamond drilling at this time would also amount to completing 75 underground holes, totalling 3,617 m in length. Sampling of the underground workings were undertaken as a metallurgical plant was developed on-site at the time. Almost all development which was aimed at continuing the drift section from 1972 to 1975, as explorations had continued. No production was achieved during this time period as sampling was only conducted at this time.
Further exploration work was done on this property from 1975 to 1976, which resulted in geological mapping, geochemistry samplings, EM and Gravity Surveying. This had also utalize a bulldoze that was commonly being used for trenching purposes in order to test mineralized areas that surrounded the Tom Adit Property. Primary tagets were mainly aimed at finding better ground for large deposits of Zinc-Lead-Silver. Follow ups on exploratory work were made from 1976 to 1977, when five surfaces holes were drilled, totalling 587 m in length. This was also followed by a 1978, diamond drilling program that amounted to 15 surface holes, totalling 2,295 m in length.
Hudson's Bay Exploration had also staked claims to the south which were registered under Tom cl 147-183. that are now known as YA45447. Explorations on this portion of the property had continued to take place when geological mapping, and geochemistry sampling was done 1979 to 1981. Exploration work had also continued to progress onward when magnetometer surveying and bulldozer trenching was done to prospect further mineralization on the Tom Adit Property.
Hudson Bay Exploration would end up staking another claim known as TS Cl, which is registered as claim YA42414, and located to the north of the Tom Adit Zones. Test pitting at the time was also commenced on this portion of the property that results in testing known mineralization that was discovered through geological mapping.
It was in 1980, when the Fringe Claim that was owned by Welcome North Mines, Limited., was optioned out to Charlotte Resources, Limited. Minor exploratory work was done on this property as geological mapping and geochemistry sail sampling was undertaken on these claims. This however, did not show encouraging results and the claims were withdrawn from Charlotte Resources potential assets.
Hudson's Bay Exploration would continued to explore the Pb-Zn-Ag values within it Tom-Adit Zones in 1982. Development preparations were made as the Adit Portal which was left abandoned had become rehabilitated for the purpose of exploring the East and West Zones. Lateral development at this time had resulted in completing 120 m of drifting and a decline was driven for a distance of 923 m within the adit workings. Diamond drilling that was undertaken had amounted to 12 holes, totalling 1,457 m from the surface, and 18 underground holes, totalling 1,174 m in length. Hudsons Bay Exploration had also carried out surface trenching and a joint venture feasibility study with Aberford Resources, Limited on the Tom, and adjoining Jason Property.
By 1985, it was reported that the West Zone had amounted to 13,385,400 tonnes grading 6.53% Zn, 28.5 grams per ton in Ag, and 3.19% Pb. Additional ore reserves were also calculated within the East Zone that resulted in 2,337,100 tonnes of ore grading 9.68% Zn, 167.3 gram per ton in Ag, and 12.8% Pb. The Jason Zone had additionally contained an ore reserve calculation of nearly 8,969,695 tonnes of ore grading 7.09% Pb, 8.53% Zn, and 79.79 grams per ton in Ag. A recalculation was made on the ore-reserves within the West, East, and Southeast Zones that resulted in 9,283,700 tonnes of mineable ore grading 69.4 grams per ton in Ag, 7.5% Zn, and 6.2% Pb, using a 7% Zn-Pb cut-off grade. The total ore-reserves within the Tom Adit were calculated at 15,722,500 tonnes grading 49.1 grams per ton in Ag, 7% Zn, and 4.61% Pb.
Cominco had additionally optioned the Fringe Claims on July, 1988, and had staked the Tome Cl 1-129 to the east on August, 1988. More claims to the option were shortly after staked when Jerry Cl 1-26 to the south was added, and Mac Cl 1-12 to the north was also staked out on October, 1988. It was proven that the Tome Claim had provided more encouraging mineralization that had warrant further exploration work from geological mapping. Cominco would additionally complete geological chemical sampling on it Tome Claims. This resulted in remapping the property as a program of surface drilling was aimed at testing the extensions of the west and south-east ore zones at depth. The diamond drilling program would take three years to complete which resulted in 4 surface holes, totalling 2,226 m in 1988, 4 surfaces holes, totalling 2,175 m in 1989, 7 surfaces holes, totalling 3,578 m, and 8 surfaces holes, totalling 2,882.7 m in 1991. Diamond drilling of the eight-holes in 1991, were mainly aimed at testing peripheral geochemical and geological targets. Additional Jerry Claims were added in 1991, which resulted in exploring them by conducting a contour soil sampling program, in which Cominco had drop its options on August,
Lithology and Mineralization
The Tom Adit Property is rather associated with another type of stratibound Pb-Zn deposit that mainly consists of galena, sphalerite and barite that's in fine grained black clastic rocks of the Devono-Mississippian Earn Group. Mineralization at the Tom Adit Deposit is commonly known for occurring in three sections known as the Tom West, Tom East, and Tom Southwest Zones. Mineralization which typically occurs at the Tom Adit property is known to occur at the contact between conglomeratic submarine fan deposit of the MacMillan Past Member. Its also considered for overlying blue-grey weathering Carboniferous chery mudstone and radiolarian cherty, which is apart of the Tom Sequence. Much of the host rocks which are associated with this deposition are believed to be deposited in narrow gardens during Devonian Rifting of the Cordilleran Passive Margin overtime. These foremost deposits at the Tom Adit property are commonly confined to much smaller basins that are outlined by an outcrop pattern of cherty-pebble-conglomerates of the Macmillan Pass Member and a thicken isopach of the Tom Sequence rocks.
A detailed mapping program that was undertaken by Cominco had shown that West Zone and Southeast Zone Deposits are occupied by two separate troughs. These two separate troughs are commonly considered to flank a narrow horst block formed cherty-pebble conglomerates. It also known that these flanking wedge out against the horst block and substancial difference in stratigraphy is known to exist between these two troughs. In addition to this, the Horst Back is considered to separate the Tom West and Tom Southeast Zones, which coincides with a tightly folded north-south doubly plunging anticline, that's determined to be apart of the Tom Anticline. A Detailed Structural Analysis reveals that three phases of folding and faulting are known to occur on this property. The much anticipated Tom Anticline is known to be among the first phased structure that has been refolded by open second phase structures with east and west axes. Second phase structures are commonly considered to be associated with low angle thrust faults and have well developed axial planar Slaty cleavage. Deformation which takes place on the Tom Adit Property is commonly related to folding and thrust faulting which occurred during the Later Jurassic and early Cretaceous periods.
The Tom West Zone is strongly confirmed as a tubular body that's 1000 m long and up to 40 m thick which dips 0.70 degrees west. For the most part, it extends down dip for 360 m and is terminated at its south end by a brecciated vent complex. This rather produce metal zoning that restricts economic mineralization to within 300 m of the vent, based on a 10% Zn-Pb cut off grade and siderite with a 25 cut-off grade of Zn-Pb. 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. 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. 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. 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.