Unable to come up with the funds to finance this year’s exploration on the Bathurst joint venture in New Brunswick,
The joint venture was in its third year of a 5-year arrangement to explore the Bathurst base metal camp for new deposits that might replace or extend the life of Falconbridge’s 41-year-old Brunswick operation. The mine, once one of the world’s largest zinc deposits, has only about four years of life remaining; it’s slated to close in 2010.
This year’s $5-million exploration program had essentially been on hold since April while Falconbridge waited for Slam to finance its share of the costs. But having spent $10 million over the past two years and with nothing to show from the 63 drill holes completed to date, the market hasn’t been too kind to Slam, recently pushing its shares to a low of 10 from a 52-week high of 63.
Slam spokesperson Bob Smylie told the local Saint John newspaper that after two years, the junior couldn’t justify spending another $2.5 million.
“It is just that there are a lot of holes that have been drilled and results weren’t showing up,” he said. “It became apparent that we needed to focus where shareholders were getting the best bang for their dollar.”
Slam was earning a 50% interest in the Bathurst joint-venture project by spending $2.5 million annually over five years. These exploration expenditures were being matched dollar-for-dollar by the provincial government under an incentive program. Falconbridge was the operator.
Noranda, now known as Falconbridge after merging with the nickel major earlier this year, had closed its exploration office in Bathurst in 2002 and turned over its digital and hardcopy exploration files to the province under a 2-year confidentiality agreement.
With much fanfare, the provincial government lured Noranda back to the province by offering a new exploration incentive package for the Bathurst mining camp, whereby the government would invest up to $2.5 million annually over five years on the condition that the private sector would provide matching funding. Only producing companies were eligible, so Slam Exploration, a Miramichi, N.B.-based junior, teamed with Noranda.
“We’re hoping such an initiative may ensure that mining continues in this region and that we will be able to find a new orebody to maintain nearly one-thousand jobs at the Brunswick mine,” said Keith Ashfield, minister of the province’s Department of Natural Resources, when the grant was first announced in October 2003.
At the provincial department’s 2005 annual year-end review, held recently in Fredericton N.B., Falconbridge’s project manager, Normand Dupras, said the joint venture was eyeing a discovery of at least 50 million tonnes, which would enable the Brunswick mill to operate at 8,000 tonnes per day for another 17 years.
Falconbridge is reportedly mulling over its options concerning the Bathurst joint venture. “We are in the process of re-evaluating everything we can do on the project,” Dupras told the Telegraph-Journal. “We may have a few opportunities with other companies or with Falconbridge; we don’t know yet because we are just into this process.”
The Brunswick mine is 27 km southwest of Bathurst in the province’s northern region. It began operating in 1964. Noranda acquired a controlling interest in the mine in 1971 and a 100% interest in 1996. The mine produces about 3.5 million tonnes of ore per year, with more than 110 million tonnes mined to date.
Proven and probable reserves at the end of 2004 stood at 17.4 million tonnes grading 8.94% zinc, 3.62% lead and 0.34% copper, plus 104.8 grams silver per tonne. Additional measured and indicated resources total 4.1 million tonnes of 8.95% zinc, 3.63% lead and 0.34% copper, plus 95 grams silver.
The deposit consists of a series of sub-parallel massive sulphide lenses that extend to a depth of 1,150 metres, with a strike length of 1,300 metres and a composite width of up to 200 metres.
Two shafts provide access to the Brunswick underground workings. The no. 3 shaft is 1,337 metres deep and is used to hoist personnel, ore and equipment; the no. 2 shaft, at 963 metres deep, carries all compressed air and water services for the mine, in addition to hoisting personnel and supplies. Production occurs on five main levels to a depth of 1,125 metres.
Mining methods are in transition from primary/secondary mining of sub-level open stopes, with delayed backfill, to pillarless, pyramid-shaped open stope sequences and end-slicing. The mined ore is crushed underground, then raised to the surface and transported to the adjacent concentrator mill. Ore is processed using grinding, differential flotation, concentrate filtering and drying technology to produce four separate concentrate products. Metal recoveries for the life-of-mine reserves are estimated at 87% for zinc, 62% for lead, 56% for copper and 55% for silver.
Mill throughput for 2004 averaged 9,405 tonnes of ore per day (the average in 2003 was 9,889 tonnes daily), resulting in production of 268,068 tonnes zinc-in-concentrate, 73,735 tonnes lead, 6,850 tonnes copper and 6 million oz. silver. For the first nine months of 2005, Brunswick produced 206,288 tonnes of contained zinc, 58,682 tonnes lead, 4,509 tonnes copper and 4.7 million oz. silver.
Of the four concentrate products, lead is the only concentrate refined in-province at Belledune, 45 km from the mine. Brunswick’s zinc, copper and bulk (combined lead/zinc) concentrates are destined mainly for Falconbridge’s smelters in Quebec and Ontario, and to European customers.
The Belledune smelter processes a wide range of offshore lead and lead/silver concentrates. A used battery recycling plant is also located on-site.
Bathurst camp
Beginning with the discovery of the Brunswick No. 6 deposit in 1952, a total of 45 deposits and 96 significant occurrences have been found in the Bathurst Mining Camp, a sub-circular area measuring 60 km in diameter. The geographic centre of the camp is about 40 km west of the city of Bathurst and 60 km northwest of Miramichi. This area is host to six former producing volcanogenic massive sulphide (VMS) zinc-lead-silver-copper mines. Currently, the only production in the camp is from the Brunswick No. 12 deposit, discovered in 1953.
About half of the discoveries in the camp were made in the 1950s and resulted from the use of geophysics, although geochemistry and prospecting proved invaluable and were responsible for some of the finds. Later discoveries in the camp can be attributed to improved exploration technology and better understanding of the stratigraphy and structure.
In the 1990s, three new deposits and some 17 occurrences or prospects were uncovered. In 1996, Noranda discovered Camel Back, a small VMS deposit in the central part of the camp, as part of a follow-up to the government and industry-supported EXTECH airborne geophysical survey. A coincident magnetic and EM anomaly was trenched and drilled in the latter part of the year. Noranda intersected 17.9 metres of massive and semi-massive sulphides, including a 4.3-metre section averaging 8.95% zinc, 3.94% lead, 0.08% copper and 41.9 grams silver per tonne, followed by a copper zone of 12.3 metres grading 2.05%. Another hole cut 5.1 metres of 8.86% zinc, 2.25% lead, 0.33% copper and 31 grams silver. Noranda outlined a 200,000-tonne resource of 5-7% combined zinc and lead.
Follow-up drilling in 1998 by Noranda on the Gilmour South prospect in the Brunswick Belt South area encountered massive sulphides grading 13.57% zinc and 7.63% lead over 2.9 metres in hole 98-14, and 9.61% zinc and 1.02% lead across 8 metres in hole 99-22.
Noranda’s 1999 discovery of the Mount Fronsac North deposit, 65 km southwest of Bathurst, showed that the potential for near-surface deposits had not been fully exhausted by some 50 years of exploration in the camp. Prospectors sent in
to investigate some high geochemical values in stream-sediment samples discovered gossan in a newly clear-cut area. Drilling traced the zone 1,200 metres along strike and more than 700 metres downdip. Massive pyrite lenses up to 45 metres thick contained intervals of sub-economic to potential ore-grade mineralization over widths ranging from 10 cm to 20 metres. The best intercept to date returned 9.51% zinc, 2.38% lead and 42 grams silver across 7.4 metres within a 16.7-metre section averaging 6.16% zinc, 1.64% lead and 28 grams silver per tonne.
Mount Fronsac North is estimated to contain 14 million tonnes of sub-economic sulphides, including a 1.3-million-tonne resource of 7.65% zinc, 2.18% lead and 0.14% copper, plus 0.4 gram gold and 40.3 grams silver.
The rocks in the Bathurst camp occur in the northern Miramichi highlands. An Ordovician-age felsic volcanic sequence sits on top of a sedimentary basement represented by the Miramichi Group. The volcanic pile is overlain by interbedded Middle to Upper Ordovician mafic volcanic and sedimentary rocks. The package of rocks in this area is classified into four groups — Tetagouche, Fournier, California Lake and Sheephouse Brook.
The Tetagouche Group, in particular the Nepisiquit Falls Formation, hosts the majority of the deposits in the Bathurst camp, including Brunswick No. 12 and No. 6, as well as Heath Steele and Falconbridge’s Half Mile Lake, which has never been mined. The Half Mile Lake deposit, in the west-central end of the camp, is a series of lenses exposed at surface along a 2.5-km strike length that has been drilled to a depth of 1,450 metres.
An Upper zone contains a 1-million-tonne resource of 7.59% zinc, 2.54% lead, 0.44% copper and 48 grams silver, while the Lower zone hosts 8.5 million tonnes grading 8.94% zinc, 2.83% lead, 0.1% copper and 39 grams silver per tonne. A North zone of about 1.2 million tonnes grades 4.51% zinc, 0.85% lead, 0.47% copper and 9 grams silver.
A new mineralized zone, called Half Mile Deep, was discovered by Noranda in 1999 while drill testing a three-dimensional seismic survey reflector. This deep zone contains a resource of 1.5 million tonnes grading 9.06% zinc, 2.16% lead, 0.11% copper and 23 grams silver.
A 2003 Slam technical report concluded that, given the “excessive depth” of the zone, the grade was not high enough to warrant further work.
The Nepisiquit Falls Formation comprises porphyritic tuff intercalated with quartz-feldspar rich volcaniclastic rocks and minor ash tuff. The volcaniclastic rocks become finer-grained near the top of the formation and are interlayered with greenish-grey, chloritic mudstone. Where iron-rich, this mudstone is described as a chloritic iron formation and referred to as the “Brunswick Horizon.”
The massive sulphide deposits are all stratiform proximal-type resting mostly within the chloritic-altered tuffaceous mudstone at or near the top of the volcanic pile. The exception is Heath Steele, which sits in the lower part of the formation.
The California Lake Group hosts a number of deposits, including the past-producing Caribou and Murray Brook mines. This group of rocks structurally overlies the Tetagouche Group but is considered coeval.
The geometry and shape of the Bathurst camp has been defined by up to five significant deformation events, resulting in intense folding and faulting. The Tetagouche Group is interpreted to have formed in a back-arc basin, with much of its structural complexity related to its amalgamation in an accretionary wedge above a westerly-dipping subduction zone. The sulphides are considered to be exhalative, formed from hydrothermal solutions venting along extensional planes in the back-arc basin, and deposited in mounds or brine pools.
Most of the massive sulphide deposits are described as having a footwall stockwork zone near the VMS, which typically rest on or within breccias or brecciated rock.
Bathurst joint venture
The premise of establishing the government-backed joint venture with Slam was to re-examine the Bathurst camp, including eastern areas overlain by Carboniferous sediments, using new, more advanced airborne and ground geophysical technology, such as the MegaTEM and Titan systems, with the hope of unlocking new riches. These sophisticated techniques can penetrate much deeper than previous surveys. Noranda used the MegaTEM technology to discover the Perseverance zinc deposit in the Matagami camp of northern Quebec in 2000. Perseverance hosts measured and indicated resources of 5.1 million tonnes grading 15.8% zinc, 1.24% copper and 0.04% lead, plus 0.38 gram gold and 29 grams silver.
The Bathurst joint venture’s area of interest covered the entire 5,249-sq.-km Bathurst mining camp and originally included 2,911 mineral claims held by Noranda and 129 of Slam’s own claims, for a total of 485 sq. km.
The joint venture divided the Bathurst camp into two regions. The west camp represents the old mining camp, the focus of much of the past exploration where some 5,000 core holes have been drilled. Exploration in the west camp is very labour-intensive and challenging, and is designed to find something new that may have previously been missed. An extensive compilation and reinterpretation of historical data is ongoing.
The east camp covers the eastward extension of the Bathurst Mining Camp stratigraphy that dips shallowly beneath Carboniferous-age sedimentary cover rocks. Recognition that the Carboniferous sandstones unconformably overlie the older prospective volcanic terrain came early in the exploration of the Bathurst camp. The Carboniferous sediments thicken very gradually to the east.
Historical drilling by Noranda and its subsidiary, Brunswick Mining and Smelting, has confirmed the presence of Tetagouche and Flat Landing Brook Group stratigraphy beneath the Carboniferous cover.
A 1990 hole drilled by Brunswick Mining and Smelting 9 km east of the unconformable contact intersected 232 metres of sandstones before cutting the Paleozoic stratigraphy. The Carboniferous cover is much more conductive than the underlying Paleozoic rocks, creating too much interference for making previous electromagnetic geophysical surveys. The bulk of the work up to now had focused on drilling magnetic and/or gravity anomalies, with much of the work carried out close to the old Key Anacon deposit. According to Dupras, there are only about 100 historic holes drilled into the Carboniferous cover on the east side of the camp. Past programs on the Cold Brook, Red Pine Brook and Bruce Siding claim groups have yielded “interesting but sub-economic” base metal mineralization, according to Slam’s 2003 technical report.
In 1992, Rio Algom Exploration intersected significant massive sulphides beneath old workings on the Key Anacon property. The property, about 19 km southwest of Bathurst, was explored in the 1950s and ’60s via a 450-metre shaft. Hole 92-10 hit 7.2 metres of 6.22% zinc, 4.49% lead and 254 grams silver at 750 metres depth, while hole 92-17 cut 14.3 metres of 12.18% zinc, 4.62% lead and 123 grams silver at a depth of 450 metres. The following year, Rio Algom discovered a new, promising zone of sulphide mineralization beneath the Carboniferous cover, 1.5 km east of the old mine site. One of the better holes intersected 19.9 metres of 7.86% zinc, 3.58% lead, 0.33% copper and 78 grams silver per tonne within an 88-metre-long sulphide intersection. Rio Algom dropped its option on the property in 1994 by not meeting its economic requirements.
The first stage of the joint venture involved a $5-million airborne geophysical program, which was completed at the end of March 2004. The entire Bathurst camp was flown with 22,400 line-km of MegaTEM II surveys, at 200-metre line spacing, and 15,200 line-km of FTG gravity surveys. The interpretation of the MegaTEM data resulted in more than 300 promising anomalies. The results of the airborne FTG gravity survey, however, were described by Dupras as “very challenging and intriguing” to interpret. Thirty-four of the airborne MegaTEM anomalies
were later re-flown with a vertical transient electromagnetic survey at a tighter 50-metre line spacing for better definition.
While the airborne surveys were under way, the joint venture added 2,991 mineral claims by staking. The provincial government also granted the joint venture exclusive exploration permits to an additional 5,118 claims covering areas that had been previously excluded from staking. As a result, the joint venture’s holdings totalled 1,828 sq. km at the end of 2004.
In the second year of the program, which ended March 31, 2005, additional ground geophysical surveys were conducted, including 60 line-km of Titan 24, a new, deep-penetrating induced-polarization (IP) and magnetotelluric (MT) system, 36 line-km of regular IP, 15 line-km of EM and 10 km of magnetic surveys. Almost 1,000 soil samples were collected and analyzed using mobile metal ion (MMI) technology.
This led to the drilling of 63 new holes for a total of 22,000 metres during the project’s second year. No significant results were reported and no new discoveries were made. The targets were all explained by the presence of sulphides or graphitic formations. Most of the drilling was done in the west camp.
“We were in the process of doing the interpretation for the east camp under the Carboniferous,” Dupras said. The joint venture completed six holes on the east side last winter, following up on previously known sulphide mineralization.
“We wanted to test-drive to see if our thinking was working,” Dupras explained. “The system is working well.”
Falconbridge applied the new Titan 24 technology, which can penetrate as deep as 1 km below surface, across the Stratmat property in the Heath Steele area, 65 km southwest of Bathurst on the west side. This area shows little conductivity but is host to the Stratmat deposits and several base metal occurrences and showings that have yielded up to 19% zinc. The Main Stratmat zone contains a previously defined resource of 1 million tonnes grading 5.35% zinc, 2.82% lead, 0.71% copper and 60 grams silver per tonne, while the S2 zone has a historical resource of 650,000 tonnes grading 8.52% zinc, 3.59% lead, 0.53% copper and 50 grams silver.
The Titan survey revealed a series of IP and MT anomalies along trend of the Barrett and MacCormak showings. Hole 60 tested a coinciding resisitivity and chargeability anomaly beneath the Barrett occurrence, intersecting 30 metres of sulphides, including 1 metre of “interesting base metal grades.”
In the area of the MacCormak showing, two separate Titan targets were drilled. The first hole cut a 5-metre-wide sulphide stringer zone, with 1 metre of 0.14% zinc. A hole into the second target intersected a 15-metre swath of sulphide stringers, including 1 metre of 0.14% zinc.
“We are in the ongoing process of rearranging our targets based on the drilling results we have from the 63 holes we did, so we are upgrading our database,” Dupras said.
Falconbridge had outlined an aggressive exploration plan to pursue in year three. This included the use of sophisticated MMI geochemical surveys to help prioritize the MegaTEM, Titan and geophysical targets being examined. Another session of drilling had been planned.
“The west camp is our main task in the drilling; we are also in progress on (defining) targets on the east camp,” Dupras said. There are currently 50 MegaTEM geophysical anomalies in the west camp waiting to be investigated. Dupras notes that there are several EM conductors close to the Stratmat, Camel Back and Flat Landing deposits that need to be tested. A 15-hole, 5,000-metre program has been proposed for the west-side properties.
On the east camp, Dupras said more than 45 km of strike length has been identified of the highly prospective Tetagouche group stratigraphy beneath the Carboniferous area, based on the geological, geophysical and diamond-drilling work completed to date. Over 30 first-priority EM and magnetic targets have been identified under the Carboniferous cover. A 35-hole, 25,000-metre campaign is proposed for the east side.
“Hopefully we will find something underneath the Carboniferous, but we still have hope for the west camp, with the Titan 24 and MegaTEM anomalies,” Dupras said.
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