As the results of mini-bulk samples collected this past winter from the Renard kimberlite cluster in north-central Quebec begin to trickle in,
The company will carry out further prospecting, heavy-mineral sampling, and geophysics to advance targets to the drilling stage. Ashton is operating the project — a 50-50 joint venture with Soquem, which has been exploring the northern half of Quebec for diamonds since 1996. The partners have found a new field of highly diamondiferous kimberlites in the Otish Mountains, 275 km northeast of Chibougamau.
In September 2001, results from heavy sampling and geophysical surveys led to the drill-testing of four anomalies on the Foxtrot property and the discovery of two diamond-bearing kimberlitic intrusions: Renard 1 and Renard 2. Since then, Ashton has drilled 16 targets and discovered nine kimberlitic bodies in the Renard cluster. All nine kimberlites are relatively small and occur within an elongated 1.5-km-long area. With the exception of Renard 1 and 7, seven of the bodies are tightly grouped inside a core area measuring less than half a square kilometre (or about 50 hectares).
Delineation drilling on Renard 5 and 6 in the winter of 2003 determined that the two kimberlites are in fact a single body, now known as Renard 65. The combined body averages a width of 60 metres over a strike length of at least 300 metres and covers a surface area of 1.5 hectares. The deepest hole ended in kimberlite at a depth of 294 metres.
Renard 1 through 8 have proved diamondiferous, and microdiamond results from Renard 9, discovered in April, are pending. At Renard 9, three holes were drilled across a geophysical anomaly 160 metres long. The body is believed to be 45 metres wide.
Based on encouraging microdiamond results, Ashton and Soquem collected mini-bulk samples of slightly less than 5 tonnes from each of the Renard 2, 3 and 4 bodies in the spring and summer of 2002, the objective being to test the potential for larger stones. The samples were processed by dense media separation (DMS) and returned an estimated diamond content of 0.67 carat per tonne (or 67 carats per 100 tonnes) for Renard 2, 1.34 carats per tonne for Renard 3, and 0.65 carat per tonne for Renard 4 — all based on a bottom-size cutoff of 0.85 mm.
In addition, DMS tests on core samples weighing less than 500 kg from the discovery holes on Renard 5 and 6 yielded a 0.92-carat and a 0.26-carat diamond, respectively. In total, 28 diamonds, each weighing 0.1 carat or better, were recovered from the DMS testing of 15.8 tonnes of kimberlitic drill core. The five largest diamonds weighed 0.92, 0.73, 0.38, 0.28 and 0.26 carat apiece.
Ashton has been encouraged by the consistent recovery of large stones from small tonnage samples, which it says provides evidence of a coarse diamond population and favourable grade distribution. “We have demonstrated that kimberlites with potentially commercial diamond content and commercial size stones are present on the Foxtrot property,” Ashton’s President Robert Boyd told shareholders at the 2003 annual meeting. “We now need to demonstrate that there’s enough potential volume of material with commercial diamond content to justify proceeding to bulk sampling.”
He added: “There are insufficient diamonds recovered to date to initiate a valuation process on the diamonds. However, the good-size stones recovered from the small initial mini-bulk samples, the encouraging percentage of relatively clean diamonds, and the favourable initial diamond contents provide strong endorsement for further work.”
Delineation drilling
Between mid-February and late April 2003, as part of a $6-million budget, the joint venture carried out delineation drilling and mini-bulk sampling on the Renard 2, 3, 4 and 65 kimberlitic bodies. About 26.5 tonnes of kimberlite were extracted by drilling 36 holes, including an additional 1.5 tonnes from Renard 2, 2 million tonnes from Renard 3, 5 million tonnes from Renard 4, and 18 million tonnes from Renard 65.
The winter delineation drilling expanded the surface dimensions of Renard 3 (145 by 25 metres, or 0.3 hectare) and Renard 4 (180 by 70 metres, or 1 hectare), while supporting the initial size estimates of Renard 2 (120 by 65 metres, or 0.6 hectare). The drilling also provided Ashton with a better understanding of the nature of the Renard bodies.
Each of these bodies has a central core portion that consists of kimberlite breccia and subordinate hypabyssal kimberlite. The kimberlite breccia has a variable country-rock xenolith content. Peripheral to the core are zones of highly brecciated and fractured country rock, referred to as country rock breccia, in addition to significant numbers of hypabyssal dykes ranging from less than 1 cm in thickness to more than 5 metres.
“If results from these new mini-bulk samples warrant, we hope to be positioned to justify a bulk sample on one or more of the core area kimberlites,” Boyd said.
So far, Ashton has completed the DMS processing of only the Renard 4 mini-bulk sample from the 2003 winter program. The 5-tonne sample collected from 10 angle holes returned 1.46 carats of diamonds larger than 0.85-mm square mesh, for an implied grade of 0.29 carat per tonne. The two largest stones are a colourless octahedral and a pale brown dodecahedral, each of which weighs 0.11 carat.
By way of comparison, the 2002 mini-bulk sample of 4.8 tonnes delivered 3.11 carats for an estimated diamond content of 0.65 carat per tonne. The four largest diamonds weighed 0.32, 0.29, 0.28 and 0.26 carat. Two of these diamonds are colourless and two are pale brown.
Tested to a confirmed depth of 240 metres, the Renard 4 body consists largely of kimberlitic breccia with varying quantities of country-rock xenolith inclusions. The xenoliths are more abundant toward the margins of the body. Ashton says drilling in 2002 sampled both the centre and the margins of Renard 4, whereas drilling in 2003 tried to define the surface dimensions of the body and therefore focused on its margins.
Hypabyssal
Collectively, the 2002 and 2003 drilling on Renard 4 yielded 8.2 tonnes of kimberlite breccia, from which a total of 4.07 carats was recovered, giving an estimated diamond content of 0.5 carat per tonne. The 2003 mini-bulk sample includes several intersections of higher-grade hypabyssal kimberlite, the widest being 14.4 metres. About 1.6 tonnes remain, and these are described as country rock and country-rock breccia containing 19% hypabyssal kimberlitic material, or 0.5 carat of diamonds, for an implied grade of 0.31 carat per tonne.
During the winter 2003 program, two additional holes were drilled across the Renard 8 body, whose geophysical signature measures 75 by 40 metres. The first hole was drilled at minus 50 and intersected kimberlitic breccia from 52-59 metres and 91-123 metres before terminating in country rock at a down-hole depth of 167 metres. The second hole was steepened to minus 60 and encountered kimberlitic breccia from 65 to 123 metres before shutting down while still in kimberlitic material, owing to drilling problems. Samples from Renard 8 will be tested for microdiamonds by caustic dissolution methods. Results are pending.
Just nine microdiamonds were recovered from a 112-kg sample taken from the first two discovery holes into Renard 8 in 2002. However, core recovery was described as poor.
“Further target drilling is planned outside the core area,” says Boyd. “Based on our data to date, we believe there is potential to find additional kimberlitic intrusives on the Foxtrot property beyond the immediate Renard cluster.”
High magnetism
The kimberlite indicator mineral anomaly emanating from the Foxtrot property is 5-6 km wide at its head. The central portion of the train can be explained in part by the Renard cluster, but Boyd says further exploration is required to explain other portions of the anomaly. Three targets
under lakes were drilled this past winter without intersecting any kimberlite.
“The northern area [of Foxtrot] hosts discovery potential, but its higher magnetic background has provided a significant challenge to prioritizing geophysical targets,” says Boyd.
In addition, the Ashton and Soquem joint-venture holds 1,040 sq. km of mineral claims in the Tichegami area, about 100 km south of Foxtrot. More than 275 heavy-mineral samples were collected on the properties during the 2002 field season in order to define highly anomalous indicator-mineral dispersion trains. Last summer, 92 line km of magnetic surveys and one standard-frequency horizontal-loop electromagnetic survey were completed over 10 anomalies on the Tichegami 1 property and five anomalies on the Tichegami 3 property. Additional ground geophysical surveys are planned for the Tichegami area in 2003.
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