Jackson Inlet, Nunavut — Canada’s High Arctic was a favoured destination for diamond exploration long before important discoveries were made in the southerly Lac de Gras region.
On the Brodeur Peninsula of Baffin Island, 100 km east of Somerset Island,
The parcel of 86 stones, exceeding 1 mm and weighing 3.644 carats, was recovered from an 18.41-tonne, mini-bulk surface sample collected from the Freightrain kimberlite this past spring under the supervision of senior manager Dallas Davis. The sample has an implied grade of 0.198 carat per tonne. A significant number of diamond fragments were noted by Lakefield, which may indicate the breakage of other, larger diamonds during either the mining or processing phase.
The largest stone weighed in at 1 carat and measured 6.98 by 5.64 by 3.6 mm. It is described as gem-quality and free of inclusions. Another stone measured 3.9 by 3.19 by 2.4 mm and weighed around 0.217 carat.
The 86 stones were examined by Antwerp-based Diamond Trading N.V., which stated that Freightrain diamonds are “similar to high-quality South African diamonds, but without having their characteristic yellow colouring.” In comparison, the Lac de Gras diamonds from the Ekati and Diavik projects are “generally octahedrons with higher occurrences of black piques [impurities] and maccles [intergrown diamond crystals].”
The Belgium rough diamond trader is a minority shareholder of Twin Mining and therefore not an independent appraiser, having taken down an equity position of 1.5 million shares late last year, representing a 2% stake. Twin Mining has about 70 million shares outstanding, or 77 million on a fully diluted basis.
“It’s a small sample and it’s early in the game,” cautioned Twin Mining’s president and chief executive officer, Hermann Derbuch, but he added that due to the consistency in the quality of the +1-mm stones, “a pattern is emerging.” However, it must be kept in mind that standard industry practices require a minimum of 5,000 carats of diamonds for valuation purposes.
Twin Mining has recovered a total of 869 stones to date, including microdiamonds, from limited surface sampling on Freightrain. Derbuch told The Northern Miner, during a recent site visit, that no boarts occur in the micros either, though there have been a few cubes.
Derbuch also said there is definitely a bias toward larger stones. Richard Roy, project manager and consultant, concurs that almost half of the +1-mm diamonds are greater than 2 mm. The percentage of large diamonds is unusual, almost double that of known producers in the world.
There also is an apparent gap in the plotting of the size distribution of the microdiamonds recovered last year. “There are two populations of diamonds,” Davis explained, “either on an aggregate basis or an individual-sample basis. The micros don’t match the macros. There has been a sampling of two sources [by the kimberlite].”
He added that there is a population of small stones (up to the 0.6-mm size fraction) that are separated from a population of larger +1-mm stones by three size fractions where only a sparse number of diamonds have been recovered. While it is possible in a single kimberlite to find multiple populations of diamond sizes, it’s unusual for the populations not to overlap.
The Jackson Inlet property lies 12 km from tidewater on the west coast of Brodeur Peninsula, 100 km west of Arctic Bay (Ikpiarjuk), Nunavut, which is linked by a 21-km all-weather road to Breakwater Resources’ Nanisivik zinc mine. There is little glacial cover and vegetation. The area is underlain by an 870-metre-thick, flat-lying package of Ordovician- and Silurian-age limestones, with minor shale beds (Cominco’s Polaris zinc mine occurs in these rocks 400 km to the northwest).
In the northern half of Brodeur, this Paleozoic package unconformably overlies a sequence of Upper Proterozoic rocks (an extension of those hosting Nanisivik). This 3,500-metre-thick series is composed of sandstones, shales, calc-alkaline volcanics and dolomite that were deposited in a shallow water, continental (or cratonic) basin. A series of northwest trending diabase dykes of Franklin age cut the rocks. High-grade metamorphic Archean gneisses form the basement rocks.
Lumina Investments (now known as Latitude Minerals) optioned 15 claims on Brodeur Peninsula in the early 1990s and began exploring for diamonds. The junior was led by Robert Hunter and Allen Achilles, though Ian Mason, a former head of worldwide diamond exploration for Cominco, directed the work programs.
While carrying out a regional program in 1993, Lumina spotted one kimberlite — or possibly two adjacent small pipes — from the air in the area now known as the Freightrain kimberlite. It was staked as Zulu-1 and presumed to be the same kimberlite discovered by Cominco in 1975.
The kimberlite stood out as two small adjacent outcrops of fractured, dark (almost black) coloured material, elevated about 2 metres above the otherwise level terrain of sandy cover. It was identified in the field (later confirmed by petrography) by the presence of purple garnets, with well-developed kelyphitic rims, chrome diopsides and olivines.
Lumina took preliminary samples from each showing for indicator mineral probe analysis, which yielded a selection of peridotitic and eclogitic pyrope garnets, and chromites. A further 80 kg of kimberlite material were shipped out at the end of the 1993 season.
Robert Hunter, Lumina’s former president, could not recall if microdiamonds were recovered from the 80-kg sample. However, Lumina dropped its option in 1996. “We never had enough dollars to go further with it,” said Hunter.
William Wolfe, former general manager of Canadian exploration for Cominco, said the company discovered several kimberlites on Brodeur Peninsula in the same period as the Somerset Island discoveries. Small samples were tested for indicator minerals and microdiamonds.
“We may well have found microdiamonds [at Freightrain],” Wolfe said, adding that the desired macros were not found. “We didn’t attach much significance to microdiamonds . . . not the way they do nowadays. This was before the widespread discovery of [the significance of] G10 garnets. Pyrope garnets and chrome diopsides were our main indicators, other than microdiamonds themselves.
“We didn’t do a lot of microprobe work,” Wolfe added. “It was in its early infancy then, so we weren’t quantitatively finding the composition of the garnets. I would be the first to admit that we didn’t adequately test these things. It just got too expensive to take it to the next phase. Cominco wasn’t committed enough to the diamond business to get in there and take 10,000-tonne samples. By 1979 or 1980, we had lost interest.”
Cominco optioned its Somerset Island properties to Cyclone Capital (now known as Nikos Exploration) in 1992. Cyclone, together with Breckenridge Resources, Westpine Metals, Westward Exploration and Alpine Exploration, picked
up additional ground on Somerset Island and carried out airborne magnetic geophysical surveys, followed by limited surface sampling on several kimberlites. Results were disappointing, and eventually, in 1997, Nikos walked away.
International Capri Resources did some regional work across Baffin Island in the mid-1990s, including heavy mineral sampling. Initial indicator mineral analysis was encouraging for two potential areas in the Borden Basin, at the northern part of the island.
Elizabeth Kirkwood’s
During a summer program in 1999, First Strike found four kimberlite boulder trains terminating in lakes, plus outcropping kimberlite around one of the small lakes, and a land-based kimberlite showing 30 metres from the lake. The processing of 25-kg samples from the outcropping kimberlite returned several microdiamonds. Drawing from the overall analysis of indicator minerals recovered from the kimberlite samples, the partners concluded that while the kimberlite is diamond-bearing, it is unlikely to be of sufficient grade to warrant further work. However, based on the analysis of some 294 stream and glacial sediment samples, indicator minerals were found in four other target areas outside of the “discovery area.”
The company later reported that these trains “contain indicators (such as ilmenites and eclogitic garnets) which are not present in the trains from the discovery area and some of which are derived from the diamond inclusion field.”
A follow-up program in 2000 uncovered kimberlite boulder trains and an outcropping kimberlite dyke in the Fabricius Fiord area. Kimberlite dykes were also found less than 1 km from the original discovery. Small samples from six of the new showings were barren of diamonds. The project has since sat idle as limited funds prevented First Strike from returning to the field.
Baffin Island first appeared on the radar screen of Twin Mining while it was conducting exploration on the Torngat diamond-bearing dyke system in northern Quebec (where it is also finding commercial-size gem-quality diamonds). In August 1998, prospector and helicopter pilot Fred Tatarnic staked three mineral claims covering the Freightrain prospect.
Davis told The Miner that Tatarnic collected three pails of weathered kimberlite from Freightrain and later panned through the sample “handful by handful on his back step” over the winter months and found a 0.768-carat, gem-quality diamond. Tatarnic later sent off a 26.45-kg sample to Lakefield Research, which recovered 13 micros and two macros. (A macro is here defined as exceeding 0.5 mm in at least one dimension.)
Derbuch said he became aware of Tatarnic’s find through Bruce Jago, the manager of the diamond laboratory at Lakefield. Tatarnic was looking for a partner for the Freightrain project.
Twin entered into a preliminary agreement in April 2000 with Helix Resources, a private company associated with Tatarnic, and acquired the rights for an initial payment of $50,000 and 30,000 shares. To maintain a 100% interest, Twin must make further payments totalling $800,000 and 345,000 shares by the end of 2006. An additional $500,000 is due upon receipt of development permits, and a further $1 million and 500,000 shares upon production of a half-million carats. Helix retains a 5% net profits interest and a 1% gross royalty.
Twin has since added to its Jackson Inlet property by staking surrounding ground, boosting its total package to 654 sq. km. Davis first visited the Freightrain prospect in May 2000 and collected 94.52 kg of weathered material from a 10-by-10-metre patch of bare snow. The aggregate sample was collected to a maximum depth of 10 cm at 17 random points, returning 39 micros and three macros.
Twin then initiated a trenching and sampling program. A total of 1,669 kg of fresh and weathered kimberlite, taken from five sites, yielded 619 micros and 62 macros. The five showings were in an area measuring roughly 360 by 100 metres.
From the air, Freightrain looks like three dark brown circular patches oriented along a northeast-southwest axis and surrounded by tan-coloured weathered material. On the ground, sparse tan-brown weathered kimberlite fragments are interspersed with predominant limestone fragments on frost boil surfaces. Last year’s mapping identified 11 other specific areas of surface kimberlite fragments in the immediate area of the five kimberlite showings.
Lakefield Research produced heavy mineral concentrates from 8-to-10-kg samples of kimberlite taken from 10 sites on the Freightrain body. The riffled samples contained anywhere from 60 to 120 grains of chromite and 90-125 grains of garnet. The grains were then probed. An average of 28% of the garnets is classified as sub-calcic, G10 chromium pyrope, whereas an average of 5% are high-pressure eclogitic garnets. An interpretation of the chromite data by Lakefield shows that an average of 46% of the chromites fall within the diamond inclusion field.
A helicopter-borne magnetometer and electromagnetic geophysical survey was flown by Fugro SIAL Airborne Surveys this spring at a line spacing of between 100 and 250 metres. Twelve magnetic anomalies were defined, including a 500-metre diameter anomaly coinciding with the Freightrain prospect.
Nine of the anomalies occur along a 30-km long linear trend and are spaced 2 to 11 km apart. The remaining three anomalies lie 20 km south of this trend. During follow-up ground work, a 21.14-kg till sample collected from over top of the Cargo 1 anomaly yielded one micro and a number of kimberlite indicator minerals, including G10 garnets and one chromite grain.
Twin Mining began a 2,000-metre first pass of drilling at the end of July by testing the Cargo 1 anomaly, which lies 4.2 km northeast of Freightrain. Collared at an angle of minus 70 degrees, the first hole successfully intersected 83.2 metres of kimberlite from 43 to 126.2 metres downhole before stopping in limestone at 152 metres. The kimberlite appears to be comprised of two distinct units. Davis says there is no visual surface expression of Cargo 1, nor any visible fragments at surface. Cargo 1 has a geophysical signature measuring 140 metres in diameter.
The drill rig has since moved to Freightrain, where nine holes have been completed to date, ranging in depth from 21 to 155 metres. “We’re drilling a line of vertical holes 50 metres apart across the feature, and we’re drilling some angle holes,” says Davis.
The nine holes have returned a total aggregate of 122 metres of kimberlite core, with the longest intercept of 63 metres coming from hole 4, which ended in macrocrystic olivine diatreme kimberlite at a depth of 141 metres. Two other holes intercepted just 18 and 15 metres of continuous kimberlite, respectively.
Hole 4 was drilled right into the highest airborne magnetic peak, which occurs roughly in the centre of the anomaly. A series of magnetic peaks occurs within the broader-based, 500-metre-wide anomaly. The first nine holes drilled into Freightrain were without the guidance of ground geophysical interpretations. The ground survey was only recently done, and the data had not been processed by the time drilling had got under way.
“It’s generally badly broken and poor drilling,” said Davis. “We can’t get very deep; it’s sandy, broken-up, fractured and it wedges in on you. If we encounter difficult situations early in the hole, we stop. It’s not an easy drilling situation.”
Adds Project Manager Roy: “But we are slowly learning. There is no problem going 300 metres with the rig that we have now.”
Several of the holes were shut down early after encountering limestone to depths of 21-30 metres. “We lost all of the holes that hit 100% limestone, because the ground was sandy and too muddy, and this caused the rods to tighten,” said David. “So rather than waste a
lot of time at this point, we stopped.”
The blocks or rafts of limestone that lie in the Freightrain kimberlite system appear to be substantial. “We expected there would be islands of limestone, but we didn’t know it would be as broken up as it is,” said Davis. Derbuch concurred: “It’s a big system, it has its complexities, and we are systematically exploring that now.”
Hole 4, Twin’s best hole drilled at Freightrain so far, encountered various degrees of altered kimberlite, with varying amounts of inclusions and nodules. The hole encountered an upper homogeneous unit of kimberlite right from surface before hitting a raft of limestone from 16 to 27 metres down-hole and passing into a phase of kimberlite that is rich in mantle-derived xenoliths. Geologist Antoine Fournier, who is logging the core, said this particular unit is full of garnet and chromium diopsides. The unit follows a limestone contact for about 80 metres down-hole. Sandstone blocks up to 5 metres in diameter are incorporated in the kimberlite unit.
Paul Sobie of MPH Consulting, which is providing advice on sampling procedures, has told Twin Mining to sample the kimberlite core sections in their entirety, while retaining 15-cm-thick representative sections of distinguishable kimberlite facies.
“We looked at sawing it and keeping half of it, but it doesn’t make sense to do that because, in this business, you need to recover as much of the diamonds as you can,” explained Derbuch.
Sobie says the size of the samples is limited because Twin is using NQ-size rods (47.6-mm core diameter), and will probably be reducing even further to BQ-size (36.5 mm). “It would be far better, in terms of getting a read on what the fine diamond distribution is, to send in the largest sample possible,” Sobie told The Northern Miner. The samples will be shipped to Lakefield Research for microdiamond analysis once the core has been logged.
Concurrent with the drilling, Twin is taking a random collection of six 50-tonne mini-bulk surface samples from test pits dug across the top of Freightrain. The samples are being collected in 1-tonne bags, which are then flown by helicopter to the estuary at Jackson Inlet for transport by ship in early September.
Before the weather turns, Davis figures they will have time to drill at least one other magnetic anomaly.
By the end of the summer field season, Twin will have spent roughly $4 million on exploration this year at Jackson Inlet. At year-end, it will have about $3.5 million in cash. The company is considering winterizing the Jackson Inlet camp and bringing in a larger-diameter, 6-inch rotary drill for a new program.
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