Joint-venture partners
The joint venture plans a major bulk-sample program designed to recover at least 6,000 carats of diamonds from three of the most promising kimberlitic pipes in the Renard cluster. Through a combination of trenching and underground mining, a minimum of 6,000 tonnes will be collected from Renard 2, 3 and 4. A highly prospective fourth pipe, Renard 9, will be further evaluated by collecting 75 tonnes from large-diameter reverse-circulation (RC) and core drilling.
“Right now these are the four (pipes) that appear to have grades that are of interest,” explains Brooke Clements, Ashton’s vice-president of exploration.
The four pipes form a higher-grade core area at the southern end of a 2-km-long trend comprising nine diamond-bearing bodies, in the south-central part of the Foxtrot property. Six of the nine bodies — Renard 2, 3, 4, 65, 8 and 9 — are clustered in an area measuring just 0.5 sq. km.
In the four highest-grade bodies (Renard 2, 3, 4 and 9) drilling has outlined 17.5 million tonnes of kimberlitic material, with the potential to contain 14 million carats of commercial-size diamonds, based on the bulk-sampling work to date. About 80-90% of the drill-indicated tonnage is within 200 metres of surface.
Three of the pipes contain more than 11 million tonnes of kimberlitic material, with grades of 0.92 carat per tonne for Renard 2 (6.5 million tonnes), 1.24 carats per tonne for Renard 3 (1.7 million tonnes) and 0.97 carat per tonne for Renard 9 (3.2 million tonnes). Renard 4, with an indicated tonnage of 6.1 million tonnes, shows an average diamond content of 0.46 carat per tonne. All of these pipes have yielded diamonds in excess of 2 carats in size.
Kimberlite has been encountered to depths exceeding 300 metres in each of the four pipes. The deepest hole is on Renard 2, which intersected continuous kimberlitic material to a depth of 565 metres.
“This is about the same height of the CN Tower,” remarked Ashton’s president, Robert Boyd, during a recent presentation to the Canadian Institute of Mining, Metallurgy & Petroleum in Toronto.
The deepest drill intercepts in the three other kimberlites range from 302 to 364 metres below surface.
By assuming the walls of the pipes are either sub-vertical or tapered inwards and are continuous to the maximum intersected depth, consultant Wardrop Engineering predicts the four bodies could contain between 23.2 and 27.6 million tonnes of kimberlitic material with as much as 18.6 to 22 million carats of diamonds.
The Renard 65 pipe, the biggest of the bunch, hosts an additional 8 million tonnes of drill-indicated kimberlite but at a much lower implied grade of 0.22 carat per tonne.
“At the moment, we are not going to knock ourselves out on that one (Renard 65),” Clement tells The Northern Miner. “It requires more drilling to determine whether there could be higher-grade zones.”
“We believe we have demonstrated, not to 43-101 standards but to standards good enough for us, that we have the potential for 20 million carats of diamonds in the ground, and that’s a lot of diamonds,” Clements says. “We really need to get a detailed handle on exactly what those diamonds are worth so we can determine what the rock value is and then do a real detailed assessment of the mining economics.”
The Foxtrot property, covering almost 2,000 sq. km in the Otish Mountains region, is centred 820 km north of Montreal and 150 km southeast of the Hydro-Qubec LG-4 generating station. The property is accessible only by air. The nearest all-weather road, 125 km to the north, services a network of hydroelectric dams. About 55 km to the south lies the idle Eastmain gold mine, formerly serviced by a 200-km-long winter road from Temiscamie on Lac Albanel. The nearest community is Mistissini, 280 km south.
Early years
Ashton and Soquem joined forces in 1996 and spent the next five years quietly conducting heavy mineral sampling across a 425,000-sq.-km area of the eastern Archean Superior Craton. More than 1,700 samples were initially taken, representing a density of about 1 sample every 250 sq. km. Only 30-40 samples contained kimberlite indicator minerals. In fact, the recovery of a lone, 4-mm-long indicator mineral grain from one of the regional samples collected in 1997 was eventually traced back to the Foxtrot property, 40-50 km away.
Within days of receiving the indicator mineral counts from follow-up till sampling in 2000, the joint venture staked the Foxtrot property. Samples containing more than 1,000 indicator minerals were collected in some of the areas. One sample was so good (it contained 9,000-10,000 mineral grains) that Ashton could not afford to wait for the indicator mineral chemistry, which turned out to be, in the words of Clements, “some of the best in North America, and as good as Lac de Gras.”
The chemical compositions of the recovered ilmenites and pyrope garnets suggested a diamond-bearing host rock. Fresh angular features and kelyphitic rims on several of the pyropes also suggested a nearby source.
The Renard 1 through 8 kimberlitic intrusions were discovered in 2001 and 2002 as a result of drilling magnetic geophysical anomalies at the head of a prominent indicator mineral dispersion train. Renard 9 and 10 were found in 2003, as was the highly diamondiferous Lynx kimberlitic dyke system, 2 km farther west. In 2005, the diamond-bearing Hibou and North Anomaly dyke systems were uncovered.
All of the Renard bodies have proven diamond-bearing and, more importantly, they show the potential to contain large gem-quality stones. The Renard bodies are small, irregularly shaped kimberlitic intrusions ranging from 0.3 to 1.5 hectares in surface expression. They are interpreted to be steep-sided, pipe-like structures composed mainly of diatreme-like kimberlitic breccia lithology and hypabyssal macrocrystic kimberlitic material.
Since the intrusion of the Renard bodies, some 632 million years ago, Ashton believes the pipes have been eroded down 1 km or so to a level somewhere in the transition between hypabyssal and diatreme facies in the lower diatreme or root zone. Glacial overburden in the area of the Renard cluster ranges from less than 1 metre to 20 metres deep.
In light of further drilling in 2005, Renard 10 is reinterpreted to be a zone of multiple kimberlitic dykes up to 20 metres thick that extends for a strike length of at least 350 metres. Two samples of drill core from Renard 10 totalling 237 kg have delivered 127 microdiamonds, the largest stone caught on the 1.18- to 1.7-mm sieve size screen. Results for an additional 200 kg of drill core collected last summer are pending.
Positive results from mini-bulk sampling of the Renard kimberlites in 2002 and 2003 prompted a further evaluation of the bodies. During 2004, a 664-tonne bulk sample was collected from Renard 2, 3, 4 and 65 through core and RC drilling, resulting in the recovery of 459 carats of commercial-size diamonds exceeding 1 mm in size.
The parcel included 25 stones larger than 1 carat. Eight weighed more than 2 carats each, including a 4.3-carat gem-quality, octahedral-shaped diamond recovered from Renard 3. The largest diamond recovered up to that point had been a clear, 4-carat octahedral found embedded in a piece of drill core from the Renard 65 body.
The recovered parcel of Renard diamonds exhibited good colour overall and were free of low-value industrial-grade boart. Based on valuations done in early 2005, it was determined that this 459-carat parcel of rough diamonds would fetch an average price of US$70 per carat on the open market.
Two diamonds, the 4.3-carat and a 2.3-carat octahedral, both from Renard 3, were valued at US$6,700 and US$3,000, respectively. The two diamonds, while accounting for only 1.5% of the parc
el weight, contributed 30% of the overall value.
Since the parcel of diamonds is relatively small, WWW International Diamond Consultants modelled an average value of US$88 per carat for the Renard run-of-mine production based on a predicted price range of between US$76 and US$104 per carat. WWW made a number of assumptions based on the diamond size frequency distribution that suggests larger, more valuable diamonds not fully represented in the parcel would ultimately be recovered.
“Thus, it is important to collect a much larger parcel of diamonds from these Renard bodies to increase the confidence in the actual and modelled diamond values for the Foxtrot property,” said Boyd.
The planned 6,000-tonne bulk sample should increase the joint venture’s exposure to the more valuable 2- to 10-carat range diamonds.
“Our working hypothesis right now is that it’s a homogeneous diamond population (through the Renard core area pipes),” Clement explains. “So the Renard 65 value is the same as Renard 2 value is the same as Renard 3 value. Obviously there are fluctuations in the individual (pipe) valuations in such a small parcel as this where one diamond can make so much difference, but at the scale we have been looking at, the diamonds look similar. In the next phase of valuations, when we are talking thousands of carats from each body, then we will start to get a better idea if that working hypothesis is correct, or whether there is the potential for different values in each body.”
A sample of at least 4,000 tonnes will be extracted by underground mining methods from Renard 2 and 3. Starting in the fall 2006, the joint venture plans to begin construction of a portal and the excavation of an inclined ramp to about 50 metres below surface. Horizontal drifts will then be driven out through the length of the Renard 2 and 3 bodies to recover the sample material.
Trenching on the northern end of Renard 4 during the summer 2006 field season is expected to collect more than 2,000 tonnes of kimberlitic material from the surface of the body. At Renard 4, most of the bulk-sample drilling had been focused on the southern half of the body, but during the summer of 2004, Ashton exposed an outcrop at its north end. An 8.7-tonne sample from the surface exposure held 15.4 carats of diamonds for an implied grade of 1.77 carats per tonne, compared with an overall grade of 0.4 carat per tonne based on the results of the 171-tonne bulk sample.
So far, the results suggest Renard 4 hosts a higher-grade zone on the north end. This assumption was supported by further drilling in 2005, which tested the north end to a 35-metre depth. A 460-kg core sample contained 0.47 carat of diamonds, representing a grade of just over 1 carat per tonne.
The joint venture has engaged Hatch, an engineering consulting firm, to set up a modular 10-tonne-per-hour dense media separation (DMS) plant on-site at the Foxtrot property. The test plant will be installed this summer at a site close to the kimberlitic bodies. The processing of the bulk-sample material will begin once the plant is commissioned, and continue into the first quarter of 2007.
The heavy mineral concentrates generated by the initial on-site processing will undergo final processing and diamond recovery at Ashton’s laboratory in North Vancouver. Results should start to become available late this year.
Ashton’s laboratory includes an indicator-mineral recovery and observing component, caustic dissolution circuit for evaluating microdiamond content in new discoveries, and a DMS plant for recovery of commercial-size diamonds from large kimberlite samples.
Renard 9 is about 50 metres south of Renard 4 and covered almost entirely by shallow lake water less than 2 metres deep. It’s not yet at the advanced stage of evaluation as some of the other pipes. Discovered in early 2003, Renard 9 has shown potential for large-size stones based on the initial microdiamond results from the discovery holes. An initial 212-kg sample had returned an impressive 178 microdiamonds. The largest stone was a pale brown composite crystal weighing 0.11 carat, caught in the 1.7- to 2.36-mm sieve size.
During the 2004-2005 winter program, a 12.2-tonne mini-bulk sample of Renard 9 was collected from the drilling of 18 holes. In total, 11.8 carats of diamonds exceeding a 1.18-mm cutoff were recovered, averaging 0.97 carat per tonne. The two largest diamonds were a colourless 3.58-carat composite tetrahexahedroidal crystal and a grey, 3.26-carat translucent composite.
“We have now recovered two diamonds greater than 3 carats from only 12 tonnes of material,” Boyd said earlier in the year. “This is very encouraging and suggests that Renard 9 could host a significant population of large diamonds.”
In order to increase the confidence level in the estimated diamond content and to better define its tonnage potential, a further 75 tonnes will be collected from Renard 9 this winter from drilling of both core and large-diameter RC; results are expected during the summer.
In 2005, definition drilling in the Renard core area added substantial tonnage, with notable increases in the drill-indicated tonnage of Renard 2 and 9.
“You take Renard 65 out and we came close to doubling the tonnage,” Clement says.
The joint venture also drilled a total of 10 holes into Renard 7 and 8 during last summer’s program. The data from Renard 8 suggest that this body contains a drill-indicated 1.2 million tonnes of kimberlitic material. A 6.1-tonne sample returned an estimated diamond content of just 7.7 carats per 100 tonnes (0.08 carat per tonne).
Renard 7 measures 120 by 100 metres, but has insufficient drilling to estimate tonnage. A 4.1-tonne drill sample from the body held only 2.3 carats per 100 tonnes (0.02 carat per tonne). No further work is planned for either of these bodies.
Lynx anomaly
The Lynx anomaly is a strong 4.5-km-wide indicator mineral train, which contains a healthy population of G10 garnets. One of the till samples in the Lynx anomalous area, taken in 2000, contained the 9,000-10,000 kimberlite mineral indicator grains that triggered the staking of Foxtrot. This sample returned a full suite of indicator minerals, including pyrope garnets, ilmenites, chrome diopsides, chromites, and, most importantly, diamonds.
The drilling at 15 sites at the head of the Lynx mineral train has intersected varying thicknesses of a kimberlitic dyke system over a north-northwest oriented strike length of 3.7 km.
“We haven’t done a lot of drilling, but there is potential for there to be a package that is of interest, if the grade is high enough and the diamond value is high enough,” Clements says. “Our working hypothesis is we have a linear dyke zone with a certain strike that’s continuous for 3.7 km and it does pinch and swell, and the dips change.”
Kimberlitic intercepts range from 0.9 to 2.9 metres thick along the 2-km-long southern end, while the dip of the zone varies from 10-15 degrees up to 45 degrees. In one area, the dyke system is shown to extend at least 250 metres downdip from its projected surface expression.
Microdiamond analysis of 148.5 kg of drill core samples collected in 2003 and 2004 returned an impressive 429 microdiamonds that show good diamond distribution towards larger stones.
Kimberlitic cobbles and boulders have been found on surface at more than 100 sites within the Lynx anomaly. During the analysis of a 4.6-tonne sample of kimberlitic boulders collected from the south end of the dyke system in 2004, Ashton recovered a pale brown 5.66-carat octahedron and a 1.17-carat, pale brown composite diamond, for an overall grade of 2.56 carats per tonne. Boulder samples from two other sites included a 5.7-tonne sample at the north end, which showed a diamond content of 0.46 carat per tonne, and 3.9-tonne sample that held 4.63 carats of diamonds, for an estimated grade of 1.2 carats per tonne.
The results demonstrate the strong potential of the Lynx dyke system to host high-grade material and commercial-size stones. Thi
s past summer, Ashton exposed the Lynx dyke by trenching in three places and collected a 30-tonne mini-bulk sample, which is currently being processed.
“If we get a reasonable grade, that is just going to justify more drilling,” Clements predicts. “The next step with Lynx is a big step. It is at least 50 or 100 holes to define the system more quantitatively.”
This past summer, exploration work resulted in the discovery of three new kimberlitic dyke systems. The flat-lying Hibou dyke was discovered 1.3 km west of the Renard cluster and 900 metres east of Lynx. Dipping shallowly 10 degrees, the west-northwest oriented dyke was tested by 28 holes drilled at 15 sites along a strike length of 850 metres. Drill intercepts indicate an average thickness of 2 metres.
Two samples of boulder material recovered near the projected surface expression of the newly discovered dyke and weighing 250 kg, returned a staggering 761 microdiamonds, showing a favourable distribution towards larger diamonds. Four of the largest diamonds were caught in the upper 1.18 to 1.7-mm size fraction. A larger 4.6-tonne sample of the boulder material returned 2.87 carats of diamonds exceeding 1.18 in size, for an implied grade of 0.63 carat per tonne. The largest diamond was a brown 0.44-carat octahedral crystal.
Hibou was exposed at surface by trenching and 9.9 tonnes of material was collected for DMS analysis. That sample held only 0.86 carat of diamonds, for a disappointing grade of 8.7 carats per 100 tonnes (0.09 carat per tonne). A 105-kg sample of the same material was analyzed by caustic dissolution methods, returning 225 microdiamonds.
The North anomaly is 5 km north of the Renard cluster. Till sampling within the confines of this anomaly has returned favourable eclogitic pyrope garnets, along with six microdiamonds, which is the best indicator of all. Drilling at three sites resulted in the discovery of a shallow-dipping kimberlitic dyke, with an average thickness of 1.2 metres and a strike length of 225 metres.
A cumulative 56.5 kg sample of drill core yielded a significant 662 microdiamonds, but more than 50% of the stones are interpreted to be fragments from the breakage of a much larger diamond exceeding 2 mm in size.
There are two other indicator anomalies containing kimberlitic cobbles and pebbles in the North anomaly that require follow-up work.
Ashton also drilled two holes into a linear feature, with an associated indicator mineral anomaly, 20 km northwest of the Renard cluster. A 20-cm kimberlitic dyke intersection was recorded in each hole.
“2005 was a really big year, with three new dyke systems, one of them 20 km away, which opens up the exploration potential of the property a little bit,” says Clements.
There are several other unresolved strong indicator mineral results, with associated kimberlite float and diamonds in till, that suggest the potential for new additional discoveries.
The joint venture is getting ready to begin mobilization for its winter 2006 exploration program, which will start with ground geophysical surveys in preparation of drilling. The drilling will focus on further defining the known dyke systems and the testing of new targets.
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