Geology and gold inventory of the Swayze Deposit, Swayze Greenstone Belt, Ontario

CIM Bulletin, Vol. 80, No. 907, 1987

G. HARPER and FT. MANNS, Northgate Group of Companies, Toronto, Ontario

The Swayze gold mine is an Archean vein deposit in northern Ontario. The veins are superimposed on a conjugate joint system and are contained within an anastomosing alteration envelope in a metadiorite body. Reserves were estimated on the basis of fire assays of channel samples and carload samples from underground mine openings, surface and underground diamond drilling and surface trenching. A semivariogram constructed from channel samples along one of the drifts yielded a horizontal, regionalized influence of approximately 9.0 m. Common industry practice has been to use 6.1 m for similar deposits in Ontario. Proven ore was defined from underground openings. The maximum extrapolation distance for proven ore along strike and dip from a data point is taken to be 6.1 m. Probable ore is extrapolated 7.6m from a data point in a mine opening or from a drill intersection. Possible mineralization is based on geological continuity one-half the distance to a neighbouring data point. The mineral inventory estimate of 1.45 million tonnes at a grade of 4.8 g A u/tonne gives an excellent outline of the geology of the deposit. The deposit contains 313 000 tonnes of ore reserves at a fully diluted grade of'6.9 gAu/'tonne. These figures include dilution for several reasons: (1) a 2.1 m mining width is used rather than the more typical 1.5 m width to allow for over-break because of the shallow dip of some vein zones; (2) over-break is allowed for adjacent to major unmineralized dykes; and (3) grams of gold are deleted from estimates to allow for the mining of unavoidable minor dykes. A personal computer with off-the-shelf software was used to compile 712 geologically defined ore blocks and sort them into a number of revealing categories. The computer was used to perform grade sensitivity tests, as well as to evaluate depth potential. Hopefully, the reiterative aspect of the method has randomized the errors and helped to cancel their effects.
Keywords: Orofino, Swayze, Ontario, Archean volcanics, Diorite, Gold, Quartz veins, Alteration, Structure, Ore controls, Reserves, Calculations, Computer.