Definition drilling by
Cumberland has embarked on a $4.5-million program designed to move the project forward to the feasibility stage. The aim of the 2-phase program is to add 400,000 oz. to support a proposed 10-year mining plan, improve resource definition, and provide feasibility-level metallurgical and geotechnical data.
Situated 70 km north of the ocean-accessible community of Baker Lake on the western shore of Hudson Bay, the property has five known gold deposits which host measured and indicated resources of 1.4 million oz. in 7.8 million tonnes grading 5.79 grams gold per tonne. An additional 1.6 million oz. contained in 10.9 million tonnes grading 4.44 grams gold are inferred.
The Meadowbank project covers some 330 sq. km of ground along a 25-km-long trend of gold mineralization. Four of the deposits (Third Portage, North Portage, Goose Island and Bay Zone) occur along a 3-by-1-km trend in and around the Portage Lakes, whereas the Vault deposit sits a further 5 km to the northeast.
The deposits are hosted in Archean greenstone supracrustal rocks of the Woodburn Lake Group in the Rae Craton of the western Churchill structural province. The Meadowbank area is underlain by a structurally complex, folded package of intermediate volcaniclastics and greywacke, with interbedded magnetite-chert iron formation and lesser pelitic schists. Gold mineralization in the main deposit area, near Third Portage Lake, occurs predominantly in iron formation with associated pyrrhotite and lesser amounts of pyrite. These sulphides occur as a replacement of magnetite in the oxide iron formations.
The outlying Vault deposit is a moderately dipping shear zone in volcaniclastic rocks, with associated pyrite, sericite and carbonate.
Cumberland first acquired a 60% interest in the Meadowbank project, along with a half-interest in the Meliadine and Parker Lake projects, from Asamera Minerals in mid-1993 for $450,000 cash and a 2% net smelter return royalty, which was later bought out for $400,000 plus shares. At the time of the purchase, Meadowbank hosted a preliminary resource of 209,000 oz. contained in the Third Portage deposit. In 1997, Cumberland acquired sole possession of Meadowbank, which had grown to exceed a million ounces, by buying-out Comaplex Minerals’ 40% interest for $3.2 million cash and 1.5 million shares plus warrants. Today Meadowbank contains more than 3 million oz. Exploration costs since 1995 total $16.5 million, which translates into a discovery cost per ounce of $6.10.
In March 2000, prior to the discovery of the Vault deposit, MRDI Canada completed a prefeasibility study that indicated the project either needed a higher price of gold or more ounces to meet a minimum mine life of 10 years, based on a 2,500-tonne-per-day milling operation producing 160,000 oz. annually. MRDI estimated total resources for the original four closely spaced deposits of 11.2 million tonnes averaging 5.73 grams, equivalent to almost 2.1 million oz.
Broken down individually:
r the Third Portage deposit contains 1.3 million oz. in 7.4 million tonnes grading 5.53 grams gold;
r Goose Island hosts 365,500 oz. in 1.2 million tonnes grading 9.74 grams gold;
r North Portage contains 2 million tonnes grading 4.49 grams, or 291,800 oz.; and
r the Bay Zone stands at 684,000 tonnes grading 4.71 grams, equal to 103,400 oz.
Looking to add ounces, Cumberland began targeting several mineralized occurrences to the north, zeroing in on the Vault area where a number of boulders were running up to 20 grams. Two rounds of widely spaced drilling at Vault during 2000 and 2001 outlined an inferred resource of 7.5 million tonnes grading 3.9 grams, equivalent to 936,700 oz.
In the fall of 2001, MRDI was commissioned to complete a preliminary scoping study, incorporating the added ounces of the Vault deposit. By increasing the design throughput rate to 4,700 tonnes per day (or 1.7 million tonnes per year), annual production rises to 246,000 oz. at a projected cash cost of US$168 per oz. and a total cost of US$235 per oz.
The proposed mining plan incorporates three open pits: a single large pit combining the Third Portage, North Portage and Bay Zone deposits, and two satellite pits on the Goose Island and Vault deposits. Deeper resources at Goose Island and Vault will be mined by underground methods.
The mine model is based on measured, indicated and inferred resources of 14.4 million tonnes grading 4.86 grams, equivalent to more than 2.2 million oz., for a mine life of 8.3 years. About 85% of the modelled resource is minable by open-pit methods to a depth of 150 metres below surface, at a stripping ratio of 7.8-to-1.
The Third Portage area deposits occur, in part, under a shallow lake at a depth of less than a couple of metres. Cumberland is proposing to construct a series of coffer dams around the proposed pits in the lake area. The company recently completed a geotechnical program on the dyke designs, drilling off the foundations of the dykes.
The metallurgy of the two deposit areas is said to be excellent and the blending of the resource should not pose any problems. Gold recoveries for the four original Meadowbank deposits average 92.4%, whereas Vault mineralization is somewhat lower at 82%. Further metallurgical tests are being conducted on the Vault to determine if recoveries can be improved.
With capital costs estimated at US$123.5 million, Meadowbank offers a payback period of 4.9 years based on a gold price of US$300 per oz. The project currently falls about 400,000 ounces short of a 10-year mining plan which Cumberland needs to ensure a sufficient payback. “We believe we need an extra two years of mine life, and we do need an extra 400,000 oz. to get to a 10-year mine life, and that’s our hurdle,” President Glen Dickson told delegates attending the annual convention of the Prospectors & Developers Association of Canada, in March.
Cumberland is spending $2.5 million during a first-phase diamond drilling program this spring at Meadowbank, targeting the expansion potential of the Third Portage, North Portage and Vault deposits. In all, some 8,100 metres of drilling are planned. With about another two weeks remaining before spring break-up, Kerry Curtis, senior vice-president, figures crews will be able to drill another 18-25 holes in the Connector zone area, depending on ice conditions. The Connector zone is a newly dubbed area, which lies between the Third Portage and North Portage deposits. The two deposits are separated by a 150-metre-long gap.
Assay results have been reported for the first 13 holes drilled along the outer edges of Third Portage and North Portage. Drilling on the northeastern edge of the North Portage deposit has intersected 44.75 grams across 6.7 metres (including 175.6 grams over 1.46 metres) at 45 metres below surface in hole 397. Stepping out 50 metres to the east along the Connector zone, Cumberland hit 12.3 grams across 6.9 metres (including 22.1 grams over 3.3 metres) at 47 metres below surface in hole 387. The next hole, a further 100 metres to the east, cut 2.77 grams across 2.7 metres at 55 metres of depth in hole 386.
A series of four holes, drilled 50 metres apart, have extended the boundary of the Third Portage deposit to the northwest. Hole 390 intersected 3.2 metres of 18.5 grams at 32.5 of depth; hole 385 pulled 5.1 metres of 14.1 grams (including 146 grams across 0.42 metre) at 36 metres vertical depth; hole 388 hit 6.4 metres of 7.23 grams (including 86 grams over 0.28 metre) at 37 metres below surface; and hole 394 cut 9.9 metres of 6.5 grams at 21 metres depth.
“With these outstanding grades, well above the average grade of the five gold deposits at Meadowbank, the Conn
ector zone will play an instrumental role in the feasibility of the Meadowbank project,” states Curtis.
Twelve widely spaced holes were sunk at the Vault deposit, which remains open at depth and to the south. The drilling tested the Vault resource at deeper levels. Results have only been reported for the first three holes, and these include 16.1 grams across 4.9 metres (including 228 grams over 0.29 metre) at 298 metres below surface in hole 51, which stepped out more than 100 metres away from any previous drill hole. The other two holes intersected 11.25 grams over 1.1 metres at 356 metres of depth in hole 47 and 8.95 grams across 2.7 metres at 175 metres below surface in hole 48.
“The possibility of further expansion drilling is open, and we are positioned for follow-up drilling at the Vault in the summer months,” says Curtis. “We are well on the way to adding the ounces we targeted for this year.”
Cumberland is compiling data from a 411-hole overburden drilling program, which targeted a 5-km unexplored area that stretches between the original four Meadowbank deposits and the Vault deposit. “We literally have about 3,000 [geochemical] samples to work through, plus the gold grain analysis, which will take a little longer,” says Curtis. The geochemistry results from the till, along with the bedrock data from the overburden hole, will give Cumberland a database for target generation to use in conjunction with the results of an airborne geophysical survey flow last fall.
Some 5,000 metres of drilling are budgeted for this summer, including infill drilling on the Vault deposit and several thousand metres dedicated to following-up the overburden program. Curtis also wants to follow-up on the PDF target, 7 km north of Vault. Several years ago, Cumberland tested this prospect and intersected 7.5 grams over 2.5 metres at 20 metres below surface.
Before the start of summer drilling, a new, larger camp will be constructed in preparation for further development. The company also intends to build a small airstrip on site. In addition, environment and metallurgical studies will continue over the summer months.
Be the first to comment on "Cumberland cuts high grades at Meadowbank"