 |  Property Description and Location
The Mactung property is located in the Selwyn Mountain Range and covers the area around Mt. Allan on the Yukon/NWT border, approximately eight kilometres northwest of MacMillan Pass. The nearest settlement accessible by road, Ross River, is 250 km away to the southwest along the Canol Road, a drive that takes about six hours. The property is located at latitude 63º17'N and longitude 130º10'W, and the Cantung Mine is approximately 160 km to the south.
NTS Area: 105O/08
Latitude/Longitude: 63.2847°N 130.1528°W
Ore Type: oxide
Resource Estimation: 33Mt @ 0.88%WO3
Access: Canol Road; gravel road from Ross River YT; hiking trail from Norman Wells, NT
Project Status: Feasibility
History
The Mactung deposit was discovered in 1962 by James Allan, a geologist of Amax Northwest Mining Co. Ltd. (Amax), probably as a result of follow-up prospecting to a regional stream sediment survey carried out as part of the Ogilvy Reconnaissance Project. The deposit was originally known as MacMillan Pass Tungsten and then as MacMillan Tungsten before it became known as Mactung.
During the years 1963 to 1967, Amax completed geological mapping, rock geochemical sampling, magnetometer surveying, and grid geochemical soil sampling on the property. The five surface diamond drill holes completed in 1968 (1,513 m) were followed by 11 km of access road construction from the Canol Road to the property in 1970. Twenty-one surface diamond drill holes were drilled in 1971 and 48 holes in 1972. In 1973, an adit was collared at the 1,890 m elevation and 726 m of lateral development and 27 m of raising were completed in the Lower Zone. A 295 tonne bulk sample was sent for metallurgical testing. A total of 43 underground holes were drilled from the adit to better define the mineralization in the Lower Zone, stratigraphically known as the "2B" horizon. Further surface diamond drilling was done in 1979 along with another 49 m of underground development. The last surface drilling conducted by Amax was in 1980. Ongoing environmental and feasibility studies continued until 1985, when falling tungsten prices caused work on the project to stop.
Amax sold the Mactung property to Canada Tungsten Mining Corporation (CTMC) in 1986 as part of a larger sale that also included the Cantung mine. CTMC merged with Canamax Resources and Minerex Resources in 1993, to become Canada Tungsten Inc. In August 1994, Aur Resources Inc. (Aur) purchased a 48% interest in Canada Tungsten Inc. and subsequently, in January 1997, the two companies merged. In October 1997, the property, along with the Cantung Mine and other Aur assets, was sold to NATCL, the present owner.
In 2005, NATCL drilled 25 surface diamond drill holes (6,639 m) to better define the west end of the deposit and to upgrade the resource classification of some mineral resource blocks from the "Inferred" to "Indicated" category.
Geology
The Mactung deposit is located in the eastern Selwyn Basin, an outer miogeoclinal basin that formed on the then western margin of the North American continent. The dominantly thin-bedded siliciclastic rocks (shale, chert, and basinal limestone) grade to the northeast into the thick-bedded carbonate sediments of the variably subsiding Mackenzie Platform. Local stratigraphy of importance may include the Late Cambrian to Early-Middle Ordovician Gull Lake Formation (dolomitic siltstone and mudstone, slate, limestone conglomerate) and Rabbitkettle Formation (basinal silty limestone) and the Ordovician to Lower Devonian Road River Group which includes the Duo Lake Formation (black graptolitic shale, laminated chert, and minor limestone) and the overlying Steel Formation (pyritic, locally wispy laminated, siliceous, locally dolomitic mudstone to siltstone). Facies-changes between deep-water clastic rocks (shale basin) and shallow water carbonate rocks (platform) are transitional.
In Jurassic and Early Cretaceous time, the miogeocline was deformed by northeastdirected compression. The rocks of Selwyn Basin responded by thrust faulting and the development of open to tight similar folds. Structural trends generally parallel the arcuate Paleozoic shale-carbonate facies boundary. Widespread Early to Late Cretaceous granitic magmatism intruded the deformed rocks of the miogeocline. Five main intrusive suites are recognized, one of which, the Tungsten (97 ma - 92 Ma), is responsible for a string of tungsten skarn deposits along the eastern flank of the former Selwyn Basin. The rocks in the Mactung area are part of the west-trending Macmillan Fold Belt. Stratigraphy in the general area of Mactung trends generally E-W and dips from 10º to 40º to the south. The axes of large folds also trend E-W and may have a shallow westerly plunge. Several ages of high-angle normal faulting, of various orientations, are known in the area.
A stratigraphic sequence has been established on the property, with nine mappable units distinguished and designated from oldest to youngest numerically I, 2B, 3C, 3D, 3E, 3F, 3G, 3H, and 4. At Mactung, this package is comprised of approximately 230 m of shallow southerly dipping, altered limestones, shales and siltstones of Cambrian to Silurian age. The entire sequence is overthrust to the north, producing a recumbent isoclinal fold with an axis that plunges at a shallow angle to the west and to the east, away from the deposit. The Cretaceous-aged Cirque Lake stock is intruded through this sequence. The deposit and the host stratigraphy is cut and offset by numerous steeply dipping northerly trending faults with displacements of up to 30 m or more.
Mineralization
The Mactung mineralization can be characterized as a metasomatic skarn deposit formed by magmatic hydrothermal fluids originating from a Cretaceous granitic stock. The deposit comprises an Upper and Lower mineralized skarn zone separated by 100 m of hornfelsed pelitic sediments. The Lower zone, while dipping in the same general direction as the Upper zone, contains a "Z" fold with an amplitude of about 90 m. The skarns associated with the metamorphosed limestone units may be divided into two main facies: garnet-pyroxene and pyroxene-pyrrhotite. Scheelite is the economic mineral of interest at Mactung, with wolframite reported only occasionally. Chalcopyrite is main base metal found in the deposit, but is probably not of economic significance. Scheelite occurs predominantly with pyrrhotite in the pyroxene-pyrrhotite facies, wherein the scheelite content increases and grain size decreases with pyrrhotite content. Minor scheelite also occurs in the garnet facies, and is coarser grained than that of the pyrrhotite facies.
Mineral Resources and Mineral ReservesTable 1-1 Indicated Mineral Resources Estimates
North American Tungsten - Mactung Project
Cut-off
% WO3 |
KRIGED
Kt |
% WO3 |
Vertical
Thick.(m) |
Kt WO3 |
| 0.5 | 33,029 | 0.88 | 24.1 | 290 |
| 0.6 | 27,927 | 0.94 | 24.2 | 262.2 |
| 0.7 | 22,198 | 1.01 | 24.4 | 224.8 |
| 0.8 | 15,571 | 1.13 | 24.7 | 175.6 |
| 0.9 | 10,423 | 1.27 | 25.7 | 132.2 |
| 1 | 8,245 | 1.36 | 26.7 | 111.8 |
Table 1-2 Inferred Mineral Resources Estimates
North American Tungsten - Mactung Project
Cut-off
% WO3 |
KRIGED
Kt |
% WO3 |
Vertical
Thick.(m) |
Kt WO3 |
| 0.5 | 11,857 | 0.78 | 22.6 | 92 |
| 0.6 | 9,260 | 0.84 | 23 | 78 |
| 0.7 | 6,614 | 0.92 | 22.8 | 60.9 |
| 0.8 | 4,631 | 1 | 21.4 | 46.1 |
| 0.9 | 2,929 | 1.08 | 22.1 | 31.7 |
| 1 | 1,658 | 1.2 | 21.1 | 19.9 |
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