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.. ~~ <br />Mining Methods <br />Part 9 <br />Miscellaneous <br />The Resuing Method of Mining at <br />Leitch Gold Mines, <br />By G. A. \IcIGv• <br />THE LEITCH mine at Beardmore, Ontario <br />is mining a system of narrow high grade quartz <br />veins in a bedded, sheared greywacke. In the ore <br />zone the greywacke beds strike generally E-W and <br />dip 70' N. Regional shearing strikes N. 60' E and <br />dips about 65' N\V. Ko. 2 vein is a straight fissure <br />vein which strikes N. 60' E. and dips 65 to 70' \. <br />Where mined it ranges in width from 8 in. to S ft., <br />the average being about 20 in. No, 3 vein is a cross- <br />Iracture vein which strikes approximately \.•S. and <br />dips 45' R'. It is very highly folded and where <br />mined ranges from 12 in. to 30 in. in width. The <br />folding increases the effective width of the vein and <br />it is usually necessary to mine across the loops of <br />the folds rather than along them. \o. a vein is a <br />combination of fissure and cross-fracture vein. It <br />strikes generally E-11' and dips about 80' to 85' N. <br />It ranges in width from 8 in. to 5 ft., the average <br />being about 24 in. Generally, the west end is wider <br />and folded while the east end is narrower and <br />straighter. <br />Due to the bedding in the greywacke and the <br />regional shearing the wall ruck is very slabby. This <br />has made it necessary to use a method of mining in <br />which ground support of one kind or another is <br />placed immediately after the extraction of ore. Gn <br />account of the narrow widths, No. 2 vein and the <br />east end of No. 4 vein are mined almost exclusively <br />by the resuing method. No. 3 vein and the west end <br />of Nq. a vein are mined by combinations of resuing, <br />sculled open sloping and sculled shrinkage sloping. <br />The resuing method of mining adopted for the min- <br />ing of 1Vo. 2 vein will be described in detail. <br />Development drifts 6 ft. x 7 ft. are driven <br />on the vein at 150-ft. vertical intervals. Care is <br />taken to ensure that the one side of the drift does <br />not break into the hangingwall of the vein. L'nder- <br />• Manager, Leitch Gold Mines Limited, Beardmore, <br />Ontario. <br />cutting the hangingwall causes excessive 'sloughing of <br />waste and is avoided in the drifts and scopes as much <br />as possible. 1~'hen drifting is completed, two litu <br />of backs are taken down an the areshoots. These <br />may range from 50 ft. to 500 ft. in length. On each <br />lift up holes are drilled by 2 ;-in. stoper drills using <br />3-in. quarter octagon alloy steel shanks and Craig <br />detachable bits. The longest steel is about 7 ft. 6 in. <br />and five changes are used on account of the excessive <br />gauge wear. Holes are drilled in the quartz vein, <br />staggered as much as possible and spaced front f1 in. <br />to t8 in., depending on the width of the vein. ~\'aste <br />holes are drilled in the footwall side so as to make <br />a final broken width of approximately 4.5 ft. in the <br />narrow vein sections. The vein is blasted first, using <br />I in, x 8 in. 70 per cent Driftite dynamite and tape <br />fuse. About eight sticks of powder and three wooden <br />spacers are used per hole and usually not more than <br />18 holes are blasted at one time to avoid blowouts. <br />1i'hen the ore from the first lift has been mucked off <br />the track the waste is blasted from the footwall and <br />it in turn is mucked. Gardner•Denver GD9H <br />mechanical loaders and Dlancha ]!•ton battery <br />locomotives are used for mucking and tramming. <br />When the ore from the second lift of backs <br />is blasted and mucked throughout the full length <br />o[ an oreshoot timbering of backs is started. Before <br />any timber is placed slashes are made in the footwall <br />for the chutes and walls are thoroughly scaled and <br />spragged. S[ulls are set at S-ft. center. The timber <br />used is round spruce with a minimum 10-in. top. The <br />footwall end is hitched, or supported by two steel <br />pins. 5-in. x 10.in. x 30.in. headblocks aze used <br />on the hangingwall. I[ has been found that the use <br />of these headblocks prevents splitting and crushing <br />of stuns before the weight of the hangingwall is taken <br />up by the fill. The stalls are lagged with 6-in. round <br />spruce lagging. Chutes are built at approximately <br />20-ft. centers and manways at 50.ft. centers. The <br />chute gates are standard bracketed board type <br />(Figure 2). The chutes are collared, using 3-in. <br />201 <br />r. <br />~. <br />i <br />!.- <br />t <br />