The Lake Shore mine is located in the center of the Kirkland Lake camp bounded to the west by the Teck-Hughes mine and to the east by the Wright-Hargreaves mine. Lake Shore may be thought of as the "crown jewel" of the Kirkland Lake camp, for it was by far the largest gold producer, producing 8,499,199 ounces at a grade of 0.51 oz/T from continuous production from 1918 unti1 1965.
This is almost twice the total number of ounces produced from the neighboring second highest producer, Wright-Hargreaves, and represents 36% of the total ounces produced from the entire camp. Additional amounts were recovered from pillars in later years.
Harry Oakes discovered gold on claim L1557, in 1911. In 1913 Harry Oakes purchased the adjoining claim to the west (Ll6635). From 1914-1918 the No.1 Shaft was developed to 400 feet on the South (No.1) Vein Zone and 7,464 feet of underground development on levels at 100, 200, 300, and 400 feet was carried out. A 65-ton mill was installed and milling began in 1918. All work was carried out by Lake Shore Gold Mines Limited.
From 1919-1965 the mine was eventually serviced by four surface shafts and three internal shafts. The original No.1 Shaft and its extension were both inactive during the latter years of operations. The No.4 Shaft, collared at 4,325-foot level, took the workings to a depth of 8,150 feet. Underground development was carried out on 57 levels and, during the life of the mine, totaled 279,238 feet of drifting, 108,317 feet of crosscutting, and 154,547 feet of raising. Milling capacity was gradually increased to a maximum of 2,400 tons per day and production was continuous until the mine closed in July 1965. Ore from the Wright-Hargreaves Mine was treated at the Lake Shore mill from 1957 until the closure of that mine in March 1965.
High-grade ore material, on the bottom levels, was still being mined when the mine closed. Diamond drilling below these levels indicated that the ore continues and that the Main Break shows no signs of weakening at depth. Relatively low tonnage of ore at deeper levels and difficulties in mining at these extreme depths proved deepening of the mine workings to be uneconomical with the fixed gold prices of the day.
The Main Break and related sub-parallel structures strike continuously across the Lake Shore property but are offset by significant post-ore faulting along the Lake Shore fault at the east end of the property. Near surface, offset on this fault is 600-750 feet horizontally and about 325 feet vertically, with the east side moving down, and north, relative to the west side. The fault strikes about 012° and dips sub-vertically to the southeast. At deeper levels the fault appears as a strike fault and merges with the No.5 fault between the 6325 and 6825 foot levels. At the bottom levels of the mine, the strike of the fault follows the North vein.
The North, or No.2 vein is the most productive and extensive structure at Lake Shore. This structure is continuous from surface down to the 8075 foot level and has been traced by diamond drilling for 800 feet below this level. Between the 1200 and 4000 foot levels the Main Break branches into several faults. The North vein is the continuation of the Main Break at the west end of the property. At the east end of the property the Main Break is represented by the South, or No.1, vein which continues as the South vein on the Wright-Hargreaves property.
Mining on the North (No.2) vein was extensive throughout the mine. Of these zones, the area containing mixed syenite porphyry and augite syenite west of the shaft area from surface to the 5450 foot level was most productive. Occasionally sub-parallel veins were mined separately from this vein, but in places the veins are closely spaced and have been stoped together across widths up to 70 feet. Stoping was nearly continuous on the North vein from surface to the 5400 foot level where veining weakened considerably and stopped at the 6325 foot level. Another ore shoot continues below this from the 7575 foot level to the 8075 foot level, the bottom level of the mine. This ore shoot was traced by diamond drilling down to 8,500’ and showed no signs of weakening. The North vein on the 8075’ level was mined over an 807’ strike length at an average stoping width of 7.6’ and an average grade of 0.677 oz/T.
The South (No. I) vein was second in importance only to the North vein. This structure contains numerous branches and splays and related veining and is far less continuous than the North vein . The ore also was not as extensive with lower average stoping widths varying from 3 to 35 feet. Above the 1000 foot level, the South vein is regular and is sub-parallel to the North vein which is some 400 to 500 feet to the north. Below the 1000 foot level, the south vein is much less regular and less continuous until finally the ore bottoms out on the 6075 foot level.
Several subsidiary veins have also been mined in the ground adjacent to these main structures. Most of these veins occurred between the North and South veins, where they formed along tensional fractures related to fault movements.
Another significant structure, sub-parallel to the North vein, occurs some 1,200 to 1,600 feet to the north. It is referred to as the Narrows break, or No.3 vein zone, and has been drilled and explored on various levels down to the 5450 foot levels. While some high-grade intersections have been reported, no significant amounts of ore have been mined form this zone. This structure likely continues to the west and east and is called the ’05 break at the Macassa mine.
Mining at Lake Shore was almost entirely within intrusive rocks except in the upper levels of the mine to the 800 foot level, where ore was found in conglomerate on the north side of the North (No.2) vein. Most of the ore is hosted in syenite porphyry with augite syenite hosting some ore at the west end of the property. Syenite porphyry is the only rock type reported in the lower levels of the mine.
The above summary of the history of the Lake Shore Mine is taken from: STILL, A.C. 2001 Structural setting and controls of gold mineralization at the Macassa Mine, Kirkland Lake, Ontario. Unpublished Masters of Science Thesis, Queens University 151p.
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