The Dusty Mac occurrence is located 1.5 kilometres east of Okanagan Falls, British Columbia.
Exploration on the Dusty Mac dates back to the turn of the century, as evidenced by four short adits, driven on quartz veins with chalcopyrite and pyrite, and several opencuts near the western side of the property, overlooking Okanagan Falls. Native silver was discovered in veins on the property in 1966 and the property restaked. Dusty Mac Mines Ltd. acquired the property in 1968. As a result of property exploration in 1968 and 1969, 61,485 tonnes of reserves graded 7.88 grams per tonne gold and 170.4 grams per tonne silver (Assessment Report 20078). The property was optioned to Noranda Exploration Ltd. in 1970. In 1974, reserves were estimated to be 120,280 tonnes of ore grading 7.06 grams per tonne gold and 123.4 grams per tonne silver, based on 3319 metres of diamond drilling. An additional 21,521 tonnes grading 4.59 grams per tonne gold and 57.59 grams per tonne silver was indicated. In April 1975, an agreement was reached for custom milling the Dusty Mac ore at the Dankoe mill (082ESW005; Tinhorn). Open pit production started August 1, 1975 and ceased in June 1976. Milling was completed June 9, 1976 and reclamation of the mine area was finished on September 21, 1976. Further exploration was carried out in 1976 by Amadeus Consultants Ltd. Canex Placer Ltd. and Scintrex Ltd. conducted induced polarization surveys in 1976 and 1981 respectively. Esso Minerals conducted exploration in 1985 and 1986. Minnova Inc. optioned the property in 1987 and conducted further property exploration until 1989. Ecstall Mining Corp. optioned the property in May, 2002.
The Dusty Mac property lies within the eastern part of the White Lake basin, a thick accumulation of Eocene Penticton Group volcanic rocks, interlayered with clastic sedimentary rocks which are largely of volcanic derivation. The Eocene rocks rest unconformably on Triassic metavolcanic and metasedimentary rocks of the Independence, Old Tom and Shoemaker formations, and Jurassic granitic intrusions. The White Lake basin forms a topographic low and is truncated by early gravity faults. The units generally dip to the east and are folded and faulted.
The hostrocks at Dusty Mac belong to the Eocene White Lake Formation of the upper part of the Penticton group. This unit consists of light coloured pyroclastic rocks, thick feldspathic andesite lahar deposits, minor andesitic lavas, and minor sandstones and carbonaceous shales. In the immediate area, these overlie older Eocene Marama Formation volcanics, composed mainly of massive rhyodacite lava.
These units are on the south limb of a southeasterly trending syncline. The beds have variable dips ranging from about 30 to 55 degrees northeast. A strong crossfracture system strikes approximately 010 degrees dipping about 80 degrees westerly almost perpendicular to the synclinal axis.
At Dusty Mac, mineralization appears to be largely controlled by an important system of reverse faults. The system trends southeast with interwoven eastern and southern striking segments and splays. The direction and magnitude of movement on these faults are indicated by large thrust slices of Marama lava which have been thrust outward and upward from the core of the syncline through several hundreds of metres of White Lake strata. In the White Lake basin, reverse faulting is thought to be the result of concentric folding and accommodation of the stratigraphic pile to bedding plane slip (Bulletin 61). Quartz veins and gossans are present in or adjacent to most of the main faults. The deposit consists of a lens-like zone of silicified volcanic rocks and sedimentary debris containing minor disseminated pyrite, native silver, chalcopyrite, galena and sphalerite. Also, some quartz veins on the property carry minor bornite and tetrahedrite.
The main mineralized zone is a gently dipping lens of quartz breccia with varying admixtures of crushed andesite. The body is exposed over a length of approximately 213 metres striking roughly 140 degrees with a central cross-section width of about 48 metres and a maximum thickness of 9 metres. A similar large lens of quartz breccia is located approximately 762 metres northwest of the main ore zone. Epithermal fluids from the Dusty Mac had a temperature of about 240 degrees Celsius, a low salinity of about 0.5 weight per cent and an oxygen del 18 value between minus 7 and minus 9 per mil (relative to standard mean ocean water). The mineralization process probably occurred at a depth of more than 380 metres (Zhang, 1986).
In 1989, five areas of mineralized and highly altered fault zones were diamond drilled (A, Adit, Chalcedony, Sawmill and the Pit zones). Alteration consists of a distal propylitic assemblage (chlorite, epidote) and more intense central alteration assemblages consisting of combinations of sericitic, argillic (clay) and potassic alteration. These inner envelopes are generally well foliated and have 2-15 per cent disseminated pyrite present. Various forms of multi-episodic silicification is present in these fault zones. Silicification varies from discrete laminated chalcedony veins to quartz breccia bodies and pervasive wallrock silicification. Commonly silicification contains pyrite, chalcopyrite, galena, sphalerite, tetrahedrite and fluorite.
In the Chalcedony zone, laminated and brecciated chalcedonic quartz veins assayed as high as 7.73 grams per tonne gold and 7.4 grams per tonne silver over 1.5 metres in drill core (Assessment Report 20078).
Total production from the Dusty Mac mine was 93,295 tonnes, grading 6.89 grams per tonne gold and 146.59 grams per tonne silver with 10 per cent dilution (Assessment Report 20078). Recovery included 606,006 grams of gold, 10,552,750 grams of silver, 2432 kilograms of copper, 2313 kilograms of lead and 242 kilograms of zinc.
In 2003, Ecstall Mining Corp. and Eldorado Gold Corp. drilled 513 metres in 5 holes beneath and adjacent to the mine. The 2003 holes were designed to test a structural reinterpretation of vein geometries in that area. Unfortunately, several of the holes did not reach bedrock due to thick overburden and were abandoned. The other holes were unsuccessful in locating the veins and Eldorado dropped the option.
In 2005, Ecstall Mining Corp conducted about 1400 metres of drilling in the mine area. Results have not been published.