Vancouver — The Red Lake area of northwestern Ontario has had its share of gold exploration booms over the past 75 years. Today, thanks to the discovery of additional reserves along the 24-million-oz. “Mine trend,” activity is once again heating up.
The first major find in the region occurred in 1925, when the Howey brothers discovered what was to become their namesake mine. The Howey operation began cranking out gold in 1930, and by 1935, another large discovery was made, this time by Madsen Red Lake Gold Mines, followed shortly thereafter by the Cochenour mine.
Beginning in the late 1940s, there was a series of staking rushes as a result of the big discoveries at Campbell Red Lake and Dickenson (now
Some 80% of the gold produced in the region comes from the 3-km-wide, southeast-trending Cochenour-Gullrock deformation zone, which forms the well-established Red Lake Mine trend, home to the Cochenour, Campbell and the Red Lake deposits.
The gold district is in a classic Archean greenstone belt, which consists of a series of metavolcanic and metasedimentary rocks. Most of the gold production has come from structurally controlled vein-type gold deposits hosted in sequences of ultramafic-to-felsic volcanics and sediments. Regionally, the belt hosts a system of at least five northeast- and northwest-trending deformation zones.
All the major mines are close to a regional mafic volcanic-sediment contact, which for years was ignored as an important control on gold mineralization. The deposits fall into three main categories: mafic volcanic-hosted; felsic intrusive-hosted; and stratabound. Most of the productive zones in the Red Lake camp are of the mafic volcanic-hosted type and occur as vein systems within a lower mafic-to-komatiitic and ultramafic volcanic sequence.
In the past, output from the Dickenson mine had been dismal in comparison to its western neighbour, Placer’s Campbell mine. The Campbell operation has produced more than 10 million oz. gold, and in 1996, Goldcorp`s mine managed to produce only 53,000 oz. at a cash cost of US$360 per oz., compared with Campbell’s favourable 320,000 oz. at US$136 per oz. At the time, Dickenson was a marginal operation at best. However, the situation changed dramatically in 1995 when Goldcorp developed an idea that the existing mineralized trend continued beyond the relatively shallow, already-mined area.
Backing up the theory with a $7-million exploration program, Goldcorp discovered the High Grade zone (HGZ) at a depth of 1.3 km below surface. By the end of 2002, reserves in the HGZ reached 1.8 million tonnes grading 80.5 grams gold per tonne, whereas reserves in the Sulphide zones totalled 1.4 million tonnes grading 12.1 grams. Additional resources of both ore types total 1.9 million tonnes grading 28.8 grams gold per tonne, mainly below 1,975 metres.
Continuing to seek out new exploration targets, Goldcorp launched the Internet Gold Rush competition in 1999. With $1 million in prizes at stake and the availability of all of Goldcorp’s geological data, contestants were asked to find the next 6 million oz. of gold on its ground. Successful entrants identified an area southeast of the HGZ as the most promising target. Goldcorp, once again followed up a theory with exploration dollars and cut up to 63 grams gold per tonne over 7.9 metres at what was to become known as the Far East zone.
The zone shows the potential to host a repeat sequence of the Red Lake deposit. Results to date continue to be encouraging, with several intersections of high-grade mineralization, including 577.4 grams gold over 1.22 metres and 122.7 grams gold over 0.6 metre, in addition to wider zones of lower-grade mineralization, including 23.3 grams gold over 6.4 metres and 18.9 grams gold over 10.4 metres.
Gold mineralization appears to be controlled by two parallel structures. The first is the upward projection of the structure hosting the HGZ, and the second is east of, and parallel to, this first structure.
In 2002, Goldcorp’s Red Lake operation produced 525,930 oz. gold at a cash cost of US$65 per oz., with an average mine grade of 78.5 grams gold per tonne. It is one of the world’s lowest-cost, highest-grade gold producers.
Operating success at Red Lake and a failed attempt to buy Placer’s Campbell property prompted Goldcorp to approve a US$85-million expansion program at the mine. According to Goldcorp, the purchase price for Campbell was around US$200 million, which made it more economical to build a new shaft and sink it towards the centre of the orebody.
The centrepiece of the expansion is a 2,180-metre shaft, which extends from surface and has a hoisting capacity of 3,600 tonnes per day. A mill expansion, which will consume US$3 million of the budget, will boost processing capacity to 900 tonnes per day.
The expansion program rides on the back of a substantial increase in reserves, which supports a production rate of 900 tonnes per day (Red Lake currently hoists and mills about 590 tonnes daily). The increase in capacity would bring the mine’s annual gold production to around 740,000 oz. About four-fifths of the ore would come from the HGZ, and the rest, from lower-grade sulphide material.
Based on a gold price of US$325 per oz. and a Canadian dollar worth US64.5, the project would have an internal rate of return of 47% and an undiscounted cash flow of US$832 million. Payback is pegged at just over a year.
The new shaft, designated No. 3 (No. 2 being an internal winze), would provide access to mineralized zones below the existing 37 Level, about 1,650 metres below surface. Most of the recently discovered mineralization is in deep zones of the deposit.
At the prolific Campbell mine, Placer stepped up the pace of exploration in the late 1990s. Faced with a depleting reserve base and low morale among its workers, the major launched an aggressive exploration program aimed at discovering ore at depth, as well as in the upper part of the deposit.
In 2001 development and diamond drilling cut several ore zones between the 30 and 32 levels; these were dubbed the 06, 51 and R zones. However, the most promising mineralization outlined came from the 30 and 42 level, in the DC, TP, M&M zones. By mid-2002, the DC zone had added 122,000 oz. of new reserves, plus 375,000 oz. of resources. Numerous areas above the 30 level remain to be tested.
Mineralization at Campbell occurs in quartz-carbonate veins and in sulphide replacements. The veins average 1.5-1.8 metres wide and extend over strike lengths ranging from 30 to 300 metres. Sulphide replacement zones vary from 3 to 12 metres in width and extend over a strike length of 120-180 metres. The gold occurs in native form or is encapsulated with sulphide minerals (mainly arsenopyrite, pyrite and pyrrhotite).
The main ore zones are the A, F, F2, L, G, P, 51, 56 and N zones. The A, F, F2 and 56 zones occur along a northwest-southeast foliation, and dip 70-80 to the southwest. The L, P, N and 51 zones are formed along the contact of the central ultramafic unit and basaltic units. The G zone is also hosted by basalt close to an ultramafic flow.
The success of the exploration and subsequent development program by both Placer and Goldcorp has invigorated the historic camp. Explorers recognize that mineral showings, thought to be limited in size, need to be tested at depth.
Despite being extensively drill-tested, only a few holes were sunk deep enough to penetrate the favourable mafic rocks. Results include up to 34.21 grams gold over 6 metres.
Rupert recently completed a $280,000 financing and, with Goldcorp working right next door, seems content to wait until the mineralized trend is better define
d.
About 1.2 km southwest of Goldcorp’s HGZ is the Headway property, being explored by Winnipeg-based
Previous drilling returned up to 85.22 grams gold over 0.61 metre, and 18.97 grams gold over 0.9 metre. Surface samples yielded values of 41.99 grams gold over 2 metres. The property contains two east-west-trending, gold-bearing structural deposits: the 1,200-by-300 metre Headway Shear and the 700-by-15 metre Main zone.
Gold is developed in quartz-carbonate tourmaline and arsenopyrite veins associated with quartz-feldspar porphyry dykes that intrude into altered and sheared mafic volcanics. Solitaire can earn up to a half-interest in the ground by spending $500,000 over the next year.
Meanwhile,
Some 1.5 km northwest along strike of the Campbell operation, partners
The pair will drill upwards of 3,000 metres to test the 1900 and LD zones, discovered in 2001 and 2002, respectively. Mineralization at each is hosted by intensely silicified ultramafic bodies and associated with disseminated sulphides (pyrrhotite, pyrite and arsenopyrite) and quartz-carbonate veins. Visible gold is common at the 1900 zone.
Past results from the 1900 zone include 76 grams per tonne over 0.7 metre in hole 32 and 25 grams over 1.7 metres in hole 27. The LD zone returned a best result of 0.68 gram over half a metre; however, only six holes were drilled, and a grab sample of outcropping quartz veining yielded a more respectable 7.75 grams.
Rubicon holds a 60% stake in McCuaig, with the remainder held by Golden Tag.
Goldcorp also has its eyes on the northern section of the Mine trend insofar as it has targeted the historic Cochenour mine and Abino prospect.
Situated 8 km northwest of McCuaig, the old Cochenour mine was in production from 1936 to 1971 and ranks as the fourth-largest and second-highest-grade mine in the district. In total, it has cranked out 1 million oz. gold from material grading, on average, 16.8 grams gold. Previous drilling by Goldcorp cut up to 777 grams gold over 3.8 metres, 331.9 grams gold over 7.3 metres, and 1,059.2 grams gold over 3.26 metres.
About 10 km to the north is the Abino prospect, which has not received any exploration since 1986. Some of the best results include 212.6 grams gold over 0.46 metre and 101.2 grams gold over 1 metre.
West of the Mine trend, Placer is earning a 55% interest in
Last year’s drilling outlined a broad gold-bearing zone some 1.5 km north of the old mine site. Highlights include 4.67 grams gold over 0.4 metre and 3.42 grams gold over 2.9 metres. Mineralization is hosted in quartz-iron-carbonate-tourmaline folded and disrupted veins, as well as in the carbonate veinlets and colloform quartz veins. The mineralized system is 300 metres wide and 900 metres long, and has been explored to vertical depths of 366 metres.
Just north of Madsen,
At Wolfden’s Nova-Co and Newman-Heyson properties,
A 2,500-metre follow-up program is testing the strike continuity of this zone, as well as several other geochemical and geophysical anomalies.
At the adjoining My-Ritt property, Wolfden has granted
Wolfden has also optioned-out the Bonanza property.
The Bonanza property is between Teck’s Howey gold property and Goldcorp’s Cochenour. The most advanced target is Sanshaw, which has received some underground development and hosts a historical reserve of 175,000 tonnes grading 6.22 grams gold, above the 114-metre level. Previous drilling on the property returned values of up to 47.3 grams gold over 5.2 metres. A 3,000-metre drill program is planned.
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