Work History

Staked as Big Thing claim (4329) and others, in 1943 by A. Brown and G. McDade, who sold the property in 1945 to Yukon Northwest Exploration Ltd. (Leitch Gold Mines Ltd.), which explored with trenching and drilling in 1946. The property was then transferred to Brown-McDade Mines Ltd., which developed the vein with 609 m of crosscutting and drifting in 1947. G.F. Dickson added Dome cl 1-7 (73538) to the west in 1958 and April 1962 and optioned them to Mount Nansen Mines Ltd. in March 1963. Control of the Brown-McDade property was acquired by Peso Silver Mines Ltd. in July 1964 and transferred to a subsidiary, Mount Nansen Mines Ltd, in 1965. Mount Nansen explored with 552 m underground drilling in 1966 and 216 m of underground development in 1967.

In 1968, Peso sold its control of Brown-McDade Mines Ltd. to Charter Oil Company Ltd. (controlled by Canadawide Investments Ltd.). Peso regained control of the Brown-McDade claims in 1978, changed its name to Rex Silver Mines Ltd. in 1979, and sold its interest in 1981 to a private syndicate. The syndicate tied on DD cl 1-66 (YA59596) to the south and east in February 1981 and transferred its interest in 1984 to a new company, BYG Natural Resources Inc.

Chevron Canada Resources Ltd. optioned the property from BYG in June 1985 and explored with soil geochemistry, EM-16 surveys, 3,717 m of excavator trenching, 1,234 m of percussion drilling (17 holes) and 638 m of diamond drilling (6 holes) in 1985; EM-16, horizontal loop and magnetic surveys, plus 3,715 m of excavator trenching and one diamond drill hole (172 m) in 1987. BYG entered into a sub-option agreement with Chevron in 1988 and drilled 75 diamond drill holes totaling 5,077 m. Metallurgical testing was done on oxidized and sulphide-bearing mineralization to determine its amenability to cyanidization. A historical resource estimate was undertaken in 1989 (not NI 43-101 compliant). In 1989, five shallow holes were drilled for soil tests on the proposed tailings dam site.

In November 1993, Gestion S.R.C. Inc. entered a letter of intent to acquire a 50% interest in the property by providing the capital and management to put the property into production, beginning with the Brown-McDade deposit. This deal did not proceed and in April 1994 BYG made an agreement with J. Malcolm Slack and Associates, a company comprised of former Noranda executives.

During the summer of 1994, BYG. drilled 6 holes (748 m) on the Brown-McDade property and 6 holes (241 m) on the neighboring Mount Nansen property (MINFILE occurrence 115I 065). In addition, the company carried out a topographic survey, geotechnical drilling (46 m) and a tailing storage study. The company also rehabilitated one of the water wells on Victoria Creek.

In 1995, BYG continued exploration and development work on their Mount Nansen Project. In preparation for mine production, BYG carried out road construction, tailings dam stripping and construction and rehabilitation of mill and mine buildings. BYG also applied for various mining permits and licenses. In April 1996, BYG received their Class A water license which allowed them to begin mining operations. Mining began on the oxidized portion of the Brown-McDade zone and the first gold-silver bar was poured in November 1996. Production rates at the end of 1996 reached 500 tonnes/day.

BYG continued mining the Brown-McDade deposit in 1997. A SAG mill was installed and commissioned in late August to replace the crushing and screening circuit. Production for 1997 totaled 617 kg (19,829 ounces) of Au and 3,068 kg Ag (98,654 ounces). The mine shut down in November 1997 to upgrade the water treatment system. The mine resumed limited production in January 1998 and full production in June 1998. In 1998, BYG recovered 472 kg (15,190 ounces) Au and 1,208 kg (38,849 ounces) Ag. Mining was suspended at the beginning of 1999 due to environmental problems and it became a Type II Minesite.

A 43-101 technical report by Middleton, 2009, summarizes the Mount Nansen and Tawa properties.

In 2019, the Yukon Supreme Court approved the sale of the Mount Nansen minesite, including the Brown-McDade occurrence, to a 50/50 joint venture of Alexco Environmental and JDS Group called the Mount Nansen Remediation Limited Partnership (MNLRP). The project will include engineering, permitting, care and maintenance and remediation (jdsmining.ca).

Regional & Property Geology

The Brown-McDade deposit is part of the Mount Nansen mine area, which is located in the Dawson Range within the Yukon-Tanana Terrane (YTT). The rocks of the YTT in this region consist of Early Mississipian metamorphic rocks separated into meta-sedimentary and meta-igneous suites (Stroshein, 1998). The meta-sedimentary suite consists of micaceous quartz-feldspar gneiss, schist and quartzite of the Nasina Assemblage with local metamorphosed carbonate noted in the Brown-McDade open pit. The meta-igneous package is comprised of biotite-hornblende feldspar gneiss and coarse-grained granodiorite orthogneiss with lesser amphibolite. These two metamorphic suites have been intruded by foliated Upper Triassic and weakly foliated Jurassic diorite, granodiorite and syenite plutons (Stroshein, 1998). In the Mount Nansen area, the Triassic to Jurassic plutons in the area are intruded by younger, mid-Cretaceous felsic plutonic rocks of the Coffee Creek Plutonic Suite and capped by the Mount Nansen Volcanic Suite coeval magic to intermediate volcanic and tuff rocks (Stroshein, 1998; Johnstone & Mortensen, 1994). Sub-volcanic feldspar porphyry dykes intrude all rock types in the area (Stroshein, 1998; Sawyer & Dickinson, 1976).

A sub-volcanic porphyry intrusive complex of the Mount Nansen Volcanic Suite occurs in the centre of the Mount Nansen property that forms an east-west zone 3.2 km long by 1.6 km wide. This complex is host to disseminated copper-molybdenum mineralization in porphyritic dykes, plugs and breccia bodies. Widespread propylitic alteration from this complex has altered the majority of rocks in the Mount Nansen area, including the Brown-McDade deposit which contains epidote, calcite, pyrite and magnetite replacement of hornblende (Stroshein, 1998; Sawyer & Dickinson, 1976).

Mining at the Brown-McDade open pit has exposed two separate and distinct deposit types. The first type is gold-silver vein mineralization hosted by a massive feldspar porphyry dyke. These fine-grained quartz-sulfide veins and breccia are enclosed by silicified and/or intensely clay-altered brecciated feldspar porphyry. The feldspar porphyry dyke has intruded along an igneous-metamorphic contact that has been mined over a strike length of 50 m in the southern portion of the pit. The second deposit type that occurs at the north end of the pit consists of a siliceous, sulphide-rich breccia in a pipe-like structure hosted by metamorphosed carbonate and clastic rocks of the Nasina Assemblage (Paleozoic). The pipe is elongate in plan with a high-grade core approximately 15 m wide and 25 m long surrounded by a low-grade envelope consisting of quartz-sulphide stringers in a silicified breccia. The deposits are separated by a northeast-striking fault which truncates and offsets the main vein-dyke mineralization.

Mineralization & Results

The ore at the Brown-McDade deposit is composed of fine-grained quartz and sulphides in narrow veins or as a matrix to a breccia of silicified and pyritized wall rock fragments. Unoxidized ore contains dark grey silica and pyrite, arsenopyrite, sphalerite, galena, sulphostalts, bornite, stibnite and chalcopyrite. Gold is genetically related to the pyrite phase of the mineralization and occurs as 5 to 50 micron-sized inclusions in pyrite grains. Oxidation of sulphide minerals extends to depths of up to 70 m and a large portion of the gold grains have been exposed by oxidation of the sulphides and post-depositional cataclastic fractures in the pyrite. The silver mineralogy is not as well understood but appears to be related to the base metal sulphide mineralization.

The 1985 exploration showed that haloes of lower grade mineralization and argillic alteration surround the high grade veins. The widest trench intersection (Trench 4) assayed 5.76 g/t Au and 63.1 g/t Ag across 22.0 m, while the highest grade (Trench 9) was 72.3 g/t Au and 79.2 g/t Ag across 6.0 m. The best drill intersection was 11.8 g/t Au and 83.0 g/t Ag across a true width of 19.6 m from Hole 85-4.

The 1986 work, which tested the northern and southern extensions of the Brown-McDade Zone, yielded disappointing results. The 1987 and 1988 work increased the density of holes in the main zone and tested it at depth. Proved open pit reserves (oxide) consist of 124,606 tonnes grading 10.42 g/t Au and 98 g/t Ag and probable underground reserves (sulphide) are 193,706 tonnes grading 14.47 g/t Au and 100 g/t Ag.

The six 1994 drill holes provided infill information to provide an updated reserve estimate for the Brown-McDade deposit. The holes typically returned lower grades and widths of mineralization than those obtained in many of the previous drilled adjacent holes. However, by design, many of the 1994 holes were drilled along the margins of the mineralized shoots where significantly lower grades and narrower widths would be encountered.

During road construction in 1996, BYG discovered a vein system parallel to the Brown-McDade zone. The vein is located within a geochemical anomaly which strikes northwest. The vein runs sub-parallel to the Brown-McDade vein and assayed 17.6 and 9.5 g/t Au equivalent over 3.05 m in trenches located 60 metres apart.

The 1996 geophysical programs were carried out over two grids; (1) the Nisling Lake and (2) the Buffalo. Both grid areas returned numerous, significant VLF-EM and magnetic anomalies, although most of the anomalies were not coincident. Financial problems at BYG prevented the company from following up any of the anomalies.

At the end of 1995 and prior to the commencement of mining published reserves for the Brown-McDade property stood at:

Open Pit - Oxide: 319 000 tonnes grading 5.30 g/t Au and 50 g/t Ag
Underground - Sulphide Ore: 298 000 tonnes grading 6.80 g/t Au and 57 g/t Ag

In 1996, BYG upgraded the on-site mill to 700 tonnes/day and added a carbon-in-pulp cyanide circuit. Previous operators at Mount Nansen were unsuccessful mainly due to poor recoveries. The addition of the cyanide circuit significantly improved recoveries. At the beginning of 1999, mining was suspended due to environmental problems. Ore reserves at the Brown-McDade property were nearly exhausted at the time of suspension.

A 43-101 technical report by Middleton, 2009, summarizes the Mount Nansen and Tawa properties. Resources are quoted for the Brown-McDade as re-calculated by Denholm et al (2000). The total INDICATED resource is listed as 126,100 tonnes grading 6. 2g/t Au and 51 g/t Ag. This appears to be for the underground portion of the No. 1 and 2 veins, and doesn't seem to include the open pittable portion of the resource mentioned earlier in the report. An additional INFERRED resources for the breccia pipe is calculated at 25,000 tonnes grading 10.7 g/t Au and 15 8g/t Ag. The summary table for the whole Mount Nansen project also includes an INDICATED resource for the Brown-McDade ore dump, calculated at 12,000 tonnes grading 5.0 g/t Au and 42 g/t Ag. This resource estimate was not filed with the securities authority and is not NI 43-101 compliant.