Tyhee Development Corp (CVE:TDC)

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Tyhee Development Corp. ("TDC") is a publicly-traded mining company listed on the Toronto Stock Exchange ( Venture). The Company is engaged in the exploration and development of mineral properties in Canada and internationally.

The Yellowknife Gold Project is located approximately 90 km north of the City of Yellowknife in the South Mackenzie Mining District of the Northwest Territories , Canada . The YGP consists of the Ormsby and Nicholas Lake gold deposits, covered by fourteen contiguous mineral leases that total 6333.33 hectares.

Yellowknife Gold Project - Resources

The Ormsby deposit resource estimate is based on a geological model for which the nature and orientation of the mineralization is derived from observation of underground and surface exposures and diamond drill core. The resource estimate conforms to National Instrument 43-101 policies. The resource has been calculated using a search ellipsoid, determined by variography, in an inverse distance to the second power model. A total of 82,514 assays were used, composited into 1.5 meter lengths. A specific gravity of 3.04 was used in tonnage conversion for the Ormsby Resource. Nicholas Lake uses a specific gravity of 2.70, an inverse distance to the second power model, and a search ellipsoid of 50 x 34 x 5 m above 100 m elevation and 60 x 40 x 5 m below 100 m elevations.

Discovery Mine Property

The Discovery Mine Property is located 88 km (53 miles) north of Yellowknife, NWT, Canada. It is a past producer of 1,023,575 ounces of gold from 1,018,786 tons of ore. A 100% interest in the 1,859 acre property, subject to a variable NSR was purchased from GMD Resource Corp in early 2001 for $265,000 (January 12, NR. Series 2, Release 13). Three principal areas of mineralization are known to exist on the Property, the Main Zone, the West Zone and the Ormsby Zone. The Main Zone and West Zones were discovered in 1944. The West Zone was developed to a depth of 152 metres (500 feet) and the Main Zone was developed to a depth of 1,235 meters (4,000 feet). Cumulatively, they accounted for all of the historic production which terminated in 1968 after the mill burnt down. Mineralization is open to depth below the shaft bottom as well as in pillars adjacent to the stopes and in stope extensions. A resource estimate for the Main Zone was completed by Goad, F.G.A.C. (1994), using incomplete historical data. It was reviewed by Pratico (1999) who restated the resource, and again by Naas P.Geo. (2001).

The Ormsby Zone was discovered shortly after the Main Zone, and was developed by Ormsby Mines Ltd. until they were acquired by Discovery Mines Ltd. in the 1950's. At that time Discovery considered the Ormsby Zone to contain 100,000 tons of ore grading 0.30 ounces of gold per ton. The mining leases lapsed in 1992 and were staked by New Discovery Mines Ltd. Subsequent exploration identified a new form of mineralization in the Ormsby Zone, which had previously not been recognized. Over 62,000 meters of diamond drilling completed since then expanded of the resources on the property resulting in the following resource estimates:

Gold Resource

A gold resource has been established at the Yellowknife Gold Project containing 16 million tonnes (measured and indicated) grading 3.60 grams per tonne gold containing 1,826,000 ounces of gold at a cut-off of 1 gram per tonne. An additional 3.2 million tonnes are inferred, grading 3.37 grams per tonne gold containing 343,000 ounces of gold (Table 1).

Global Resource

At an arbitrary 0.5 gpt cut-off, the Ormsby Zone and West Zone contain an undiluted measured and indicated 26,995,000 tonnes grading 2.30 gpt gold for 1,824,000 ounces of gold. An additional 18,146,000 tonnes grading 2.30 gpt gold for 1,341,000 ounces of gold are inferred. At an arbitrary 1.0 gpt cut-off the measured and indicated gold resource is 15,069,000 tonnes grading 3.65 gpt gold for 1,556,000 ounces of gold. An additional 9,817,000 tonnes grading 3.65 gpt gold containing 1,153,000 ounces of gold are inferred. No disseminated mineralization has been identified at the Nicholas Lake Main Zone, so it has been excluded from this calculation.

The Global Resource is determined as part of the Company’s investigation of the potential for the property to host a bulk mineable resource. The potential bulk mineable resource has been identified in two areas within the Discovery Shear Zone separated by 2 km and is open in all directions, and in part incorporates the high-grade resource reported above. Only eight wide-spaced diamond drillholes have been completed between these two zones, six of which intersected significant mineralization (fifteen significant intersections ranging up to 89.827 gpt gold over 0.61 metres with a length weighted average of 10.51 gpt gold over 0.93 metres). Details can be viewed on the Company’s website.

Mineralization outcrops along prominent ridges within the Ormsby and West Zones, and represents an excellent exploration and development target. Mineralization remains open between the two zones and to depth.

Using a higher cut-off (3.5 grams per tonne for the Ormsby and West Zones, and 5.0 grams per tonne for the Nicholas Lake Main Zone), the total measured and indicated gold resource has increased from 881,000 ounces of gold to 1,049,000 ounces of gold from 3.6 million tonnes grading 9.01 grams per tonne gold. The inferred gold resource is 426,000 ounces of gold in 1.7 million tonnes grading 8.01 grams per tonne gold (Table 2).

The changes to the resource model result from new information obtained from the underground program that has enabled Tyhee to develop continuous three dimensional access to a portion of the Ormsby Zone mineralization. The gold bearing zones are wider, longer, and more continuous than previously indicated. The strike of the individual zones are more northerly and the dips steeper than previously modeled. The reduced block size permits a more refined definition of the gold-bearing zones. To date, measured continuity of the resource blocks in the underground workings exceeds that predicted by the resource model. The decrease in the inferred resource is largely due to an upgrading of that resource to a measured or indicated category, as well as a reduced volume of rock under consideration, brought about by reducing the size of the search ellipsoid.

Gold mineralization occurs within altered northeast-striking metavolcanic breccias that dip steeply to the northwest. These domains which are silicified and sulphidized, with or without carbonate, biotite, and garnet, are up to 20 metres wide. Some exceed 100 metres in length. Higher-grade gold zones of various dimensions transect these mineralized breccias, striking north-westerly dipping moderately to the south.

A total of 256 diamond drillholes and 7 channel strings were used in the resource calculation. A total of 57,012 assays were used, composited into 1.5 metre lengths. A 210 x 150 x 50m search ellipsoid, determined by variography was used in an inverse distance to the fourth power model for the larger tonnage resource. A more restrictive 180m by 120m by 45 metre search ellipsoid in an inverse distance to the fourth power model was used in the higher-grade figure. The Ormsby Lithon incorporates a volume 1632 metres long, 224 metres wide, and 650 metres deep (open) and the Discovery Lithon incorporates a volume measuring 1210 metres long, 160 metres wide, and 422 metres deep (open). The Discovery Lithon which hosts the West Zone is considered separately.

All calculations use fire assay data which had been completed by previous operators as well as recent fire assay data collected by Tyhee. Tyhee completed fire assays on drill core and chip samples from the decline on 30 gram aliquots with ICP-ES finish at Acme Analytical Laboratories Ltd. in BC. Tyhee completed a rigorous QA/QC program of inserting blanks and duplicates in the field and standards in the laboratory. The laboratory also conducted their own independent QA/QC program including inserting their own standards and re-running samples from pulped material and reject material. These results were provided to Tyhee. Tyhee also processed check samples at ALS Chemex Laboratories in North Vancouver for additional confirmation of results. All standards, duplicates, blanks and check assays returned acceptable results.

Ongoing metallurgical studies confirm previously reported studies demonstrating gold recoveries of greater than 94% using simple bulk cyanidation or floatation plus cyanidation techniques. Engineering studies are proceeding towards a prefeasibility study. Environmental baseline studies commenced in 2004 and are continuing with the goal of submitting a project description report for regulatory review. The camp is currently operational and crews are resupplying the camp via winter road. Underground operations are planned to recommence shortly.