Yellowknife, N.W.T. —
The 64-sq.-km property, a past producer, comprises 14 contiguous mining leases. Both the Discovery showing and the Ormsby zone fall within the same mining lease and are about 2 km apart.
The Discovery mine produced 1 million oz. gold from 1 million tons between late 1949 and 1969. The mill burned down in 1968, forcing operators to truck ore to Yellowknife for processing during the final year of mining.
The area is underlain by altered mafic volcanic rock and metasedimentary rocks, which belong to the Yellowknife greenstone belt. The rock is locally folded and faulted, and the metasediments locally exhibit a transition from greenschist to amphibolite facies.
The Ormsby zone is within a volcanic package that may once have been joined with the mafic volcanic rocks along strike of Discovery. Several faults border the volcanic rocks at their contact with intervening metasediments.
The ore at Discovery came from a zone of sub-parallel gold-bearing folded quartz veins in pyrrhotite-bearing amphibolitic metasedimentary rock near a major contact with volcanic rock.
Tyhee has sampled a lot of core since 2001, when it acquired the property, and found that it is not just the quartz veins that carry gold. There seems to be a correlation between biotite alteration and the presence of gold. As well, when there is later-stage euhedral garnet or arsenopyrite, there is usually elevated gold (in the range of 5-10 grams gold per tonne).
The core is generally intersected by narrow (1-2 cm wide) quartz veins with local pyrite and pyrrhotite and the occasional fine speck of visible gold. There is evidence of two stages of mineralization: earlier sulphides have been stretched, whereas others are euhedral (having their own characteristic outward crystalline form unaltered by the other constituents of the rock).
For many years, holes were drilled perpendicular to the north-northeast-trending stratigraphy. Then it was found that quartz veining and mineralization are at a distinct angle to this. Drilling has been reoriented so that mineralization can be cut at a high angle.
Relying on extensive sampling by previous owners, some 50,500 assays were compiled into a block-model resource estimate for the Ormsby zone.
In April, Tyhee reported that Ormsby contains a measured and indicated resource of about 2 million tonnes grading 10.5 grams gold per tonne (694,271 oz. gold). An additional 1.9 million tonnes grading 10.2 grams gold are inferred, based on a cutoff grade of 5 grams gold per tonne.
The Ormsby zone has been traced for 900 metres along strike and remains open. This summer, Tyhee began developing a decline to test the zone. The ramp was developed to a vertical depth of 20 metres (almost 100 metres in length) by a previous operator. It is currently 300 metres long, halfway to the planned 600-metre mark, a target that should be reached by year-end. Up to 400 metres of lateral drifts are also being developed.
Tyhee President David Webb says the work is designed to show vertical and lateral continuity. The company has been collecting 25-kg samples from each round down the decline, and chip sampling every metre in areas where mineralization may be present.
Walking down the decline, we passed several areas with quartz veins varying in width from less than 1 cm to tens of centimetres; the veins are locally sulphidized and, we are told, nearly always carry gold. The veins often have a shallow dip (10-20). Pyrrhotite and pyrite lenses are found locally in the veins and adjacent to them. In addition, sulphide lenses and disseminated sulphide (including arsenopyrite) are present in the mafic volcanic wall rock.
Local muck samples have assayed from 3 to 9.4 grams gold per tonne. Webb stresses that this sampling only gives an indication of the mineralization, whereas chip samples, which also have been taken, provide a more accurate account of the grade. Assays are pending.
Tyhee plans to develop raises and begin drilling 3,000 metres underground.
So far this year, crews have completed 26 surface diamond drill holes (9,945 metres). Assays are still pending for eight holes. The first hole this past summer tested the eastern extent of the southern part of the Ormsby zone. Near the end of the hole, at 495 metres down-hole, a 4.5-metre intersection graded 17.5 grams gold per tonne, and at 350 metres down-hole, 12.5 metres graded 6.5 grams gold. Another hole hit higher-than-expected gold values: 13.5 metres grading 7.1 grams gold, which was included in a wider, 27-metre intercept of 4.5 grams gold at a down-hole depth of 111 metres. Additional drilling will try to determine the extent of this zone.
About 2 km northeast of Ormsby and southwest of the Discovery mine site is the West zone, which was developed when the mine was operating (to a depth of 150 metres). Last year, Tyhee drilled eight holes (1,112 metres) into the zone and estimated an inferred resource using data from three additional holes.
In total, eight holes have been drilled between the two zones, one of which Tyhee sunk this past summer. Follow-up work is warranted.
The Department of Indian Affairs and Northern Development (DIAND) has begun cleaning up the former Discovery mine area. The tailings have been capped with clay and covered by crushed rock, and an airstrip was improved. Tyhee’s camp is set in the area where the rock was quarried; the surface is level, dry and sheltered.
An ice road has been built to connect Yellowknife to the property. The road joins up with the Bluefish hydro dam, 55 km to the south. A hydro line used to run from there to the site.
DIAND will be raising the remaining town site and carting away debris, and over the next two years, the department will be building a winter road to assist in this task. Ice roads are in the public domain and can be used by anyone (apart from the ice road to the Lupin mine site, which services the operating diamond mines and for which a toll fee is charged). Last year, Tyhee had contractors put in the road, and DIAND used it. This time, Tyhee will benefit from their work.
Eight kilometres northeast of Discovery, but on the same property, is the Nicholas Lake deposit. In March 2003, the Nicholas Lake main zone was estimated to contain a measured and indicated resource of 612,000 tonnes grading 9.5 grams gold per tonne (186,767 oz. gold), as well as an inferred 210,000 tonnes grading 8.6 grams gold. The estimate is based on a cutoff grade of 5 grams gold and a minimum mining width of 1.5 metres.
A previous owner, in 1994, conducted advanced exploration, which resulted in a 615-metre decline to a vertical depth of 80 metres. Crosscuts totalling 210 metres were also developed. Royal Oak Mines bought the property in 1995 but filed for bankruptcy before mining could begin.
Gold is associated with a series of near-vertical gold- and sulphide-bearing quartz veins in a sheared granodiorite intrusion and adjacent sheared and brecciated metagreywacke. Sulphides include pyrrhotite, arsenopyrite, pyrite and local sphalerite and galena. Within the main zone are at least 15 gold-bearing veins that vary from one to several metres wide and 50 to 100 metres long.
Tyhee has 31.6 million shares outstanding, or 41.6 million on a fully diluted basis.
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