Exploration for diamonds in Quebec heated up with a massive staking rush late last year after
Since Quebec allows for map staking, pretty much everyone and his dog has picked up mineral claims around either the Otish Mountains area, 750 km north of Montreal, or the James Bay area, a further 400 km to the west, where
The Precambrian-age Superior Craton, underlying parts of Manitoba, Ontario and Quebec, is the world’s largest stable platform of ancient crustal rocks, and, as such, is viewed as being broadly favourable for the emplacement of diamondiferous kimberlite.
Between 1996 and 2000, Ashton and its partner, Soquem, a Quebec Crown corporation, completed a sampling program over a large portion of the eastern Superior Craton in northern Quebec. More than 1,700 heavy mineral samples were collected from an area measuring 425,000 sq. km, for an approximate density of one sample per 250 sq. km. The dominant medium sampled was eskers.
This work identified priority areas with anomalous concentrations of kimberlite indicator minerals. The indicator mineral compositions vary markedly, leading Ashton to believe that the mantle conditions vary geographically. Distinct pyrope garnet populations are apparent in the anomalous areas, with high-chromium, low-calcium G10 garnet populations present, varying from trace to about 16% of the total recovered peridotitic pyrope.
“Although there are notable exceptions in the world, most economic kimberlites have a significant population of high-chromium, low-calcium garnets,” Ashton’s vice-president of exploration, Brooke Clements, told delegates at the recent Cordilleran Roundup in Vancouver, B.C.
The associated picroilmenite populations are also distinct and suggest that a high degree of diamond preservation can be expected in certain areas.
In August 2000, Ashton and Soquem initially staked 1,000 sq. km of ground in two key areas: the Otish Mountains and Caniapiscau, the latter being 500 km east-northeast of Radisson. Today, the joint venture holds a total of 2,600 sq. km of mineral permits in the province.
Ashton flew a geophysical magnetic survey at a 200-metre line spacing over the heart of the Otish Mountains area in late 2000 and followed this with ground geophysics over eight targets in March 2001. In the summer, these anomalies were investigated further, with more than 350 heavy mineral samples collected. “The till sampling in the summer of 2001 dramatically upgraded the geophysical targets,” says Clements. In addition, a fist-size cobble of altered ultramafic “kimberlitic” float was found 400 metres down-ice from what was then known as anomaly 83.
In September 2001, Ashton intersected what appeared to be kimberlite in the first hole of a drilling program designed to test four of the magnetic anomalies. A vertical hole into anomaly 83 hit a 98-metre interval of ultramafic igneous rock, with characteristics that were described by Ashton as consistent with kimberlite. The hole was shut down in kimberlitic material at a depth of 108 metres, owing to budgetary constraints. A second hole, at the same site, was collared at 70 to the south; it intersected 108 metres of kimberlitic rock before shutting down while still in the unit.
This discovery, referred to as Renard 1, yielded 54 microdiamonds and five macrodiamonds from 205.8 kg of core samples. (A macrodiamond is defined here as exceeding 0.5 mm in at least one dimension.) Renard 1 is primarily hypabyssal material, with brecciated material occurring near the bottom of the drill hole.
A second kimberlitic body, dubbed Renard 2, was discovered 1 km south of Renard 2. A vertical hole intersected 83 metres of kimberlitic rock below 18 metres of overburden. The hole was terminated in the kimberlitic unit at a depth of 101 metres. A second hole drilled at an angle of 60 to the northwest intersected 13 metres of kimberlitic material to a depth of 35 metres, followed by 70 metres of mainly gneiss interspersed with lesser amounts of kimberlitic rock.
In total, 116 micros and 29 macros were recovered from 163.1 kg of core sample, including five stones greater than 0.5 mm in two dimensions. The three largest diamonds measured 1.63 by 1.58 by 0.53 mm, 1.44 by 1.05 by 0.6 mm, and 1.25 by 1.05 by 0.6 mm.
Renard 2 is a complex body that shows evidence of multiple intrusive phases, and Clements said it is best classified as a “xenolith-rich autolithic breccia, with local variations of xenolith and olivine macrocrysts.” He added that there is some minor hypabyssal material present in the holes. Two other magnetic anomalies were tested during the first round of drilling and were explained by the presence of magnetite and hematite.
The Renard discoveries are described as “kimberlitic.” Ashton uses this term in the field, usually prior to thin section work, to describe rock that has characteristics consistent with kimberlite. “It’s the type of rock you want to find when searching for a diamond mine,” said Clements. Subsequent petrographic analysis suggests the diamond-bearing rocks are transitional between kimberlite and melnoite. While similar in appearance to kimberlite, melnoite differs slightly in the chemical composition of the groundmass minerals.
The Renard bodies contain macrocrystic olivine in a groundmass hosting variable amounts of olivine, phlogopite, monticellite, perovskite, apatite and spinel. More importantly, the Renard bodies contain diamonds, along with indicator minerals including pyrope garnets and chromite. A number of the pyropes have high-chromium, low-calcium G10 chemical composition.
“By anybody’s measure, these are significant results for the first two discoveries in a new belt of kimberlitic rock,” said Clements. Although it has been 10 years since Charles Fipke and BHP Diamonds first discovered a diamond-bearing kimberlite pipe in the Lac de Gras area of the Northwest Territories, Clements believes the great era of Canadian diamond discovery has just begun. “What kind of potential do Quebec and other underexplored areas of Canada offer for new diamond discoveries?” he asks rhetorically.
Ashton and Soquem have begun a winter exploration program that includes the collection of a 1-to-3-tonne mini-bulk drill sample from Renard 2, while learning more about its size and shape through delineation drilling and additional geophysical surveys.
The results of till sampling carried out in the past two years have Ashton convinced that there are additional kimberlitic bodies in the area. Ground geophysical surveys will be conducted over some 10 airborne magnetic anomalies in the anomalous indicator mineral areas. The highest-priority targets will then be drilled. In addition, a helicopter-borne magnetic and electromagnetic survey will be flown over the Renard area to identify new targets for ground follow-up. This summer, an ambitious program of heavy mineral sampling is planned.
Majescor
Majescor Resources is Quebec’s diamond flagship, with an extensive land portfolio covering well over 5,000 sq. km. It was an early landholder in the Otish Mountains and Wemindji areas, the latter being 40 km east of James Bay. The company was spun-off from
In 1998, Virginia Gold was targeting the base metal potential of 10 unexplained magnetic anomalies selected from government regional airborne geophysical surveys, when it recovered kimberlite indicator minerals in three of the 25 till samples taken. One pyrope garnet was recovered in each of the three samples, two of which were G10s. One of the samples that kicked came from the Wemindji, whereas the other two derived from the Otish Mountains. “That got us very excited early on,” Majescor President Jacques Letendre told delegates at the
Cordilleran Roundup.
Virginia brought Letendre on board in 1999. Letendre had worked for the Canadian exploration division of
On the strength of the initial results, Majescor gradually widened the scope of its sampling campaigns to a more regional level, starting in June 1999. A broad scatter of kimberlite indicator minerals was detected at Wemindji, east of a 50-sq.-km mining exploration permit then held by Monopros (now known as De Beers Canada Exploration). Unknown to Majescor, the exploration arm of De Beers had spent at least three years carrying out extensive glacial sediment sampling, high-resolution airborne geophysical surveying and follow-up drilling. Monopros had defined a 30-km-long indicator dispersion train but drill-tested at least nine magnetic anomalies without success before abandoning the property in 2000. “They failed to find the source rock of the kimberlite indicator minerals, supposedly because of noisy magnetics,” said Letendre. Another likely explanation is that the source rock was a kimberlite dyke, and not a pipe.
Majescor re-staked the De Beers property and today holds more than 870 sq. km of ground in the Wemindji area, which is accessibe year-round via an all-weather road. “We had the luxury of selecting the ground that we wanted, based on our indicator minerals,” said Letendre.
Majescor initially carried out a 1,685-line-km helicopter-borne geophysical survey and followed-up with sampling of glacial and postglacial sediments over the bulk of the property. The junior investigated some 50 magnetic anomalies. More than 70% of the samples have tested positive for kimberlite indicator minerals. A significant number of samples have yielded indicator mineral counts in excess of 100 grains. The maximum indicator count from one sample is greater than 9,300 grains.
The indicator minerals have several features that lead Majescor to believe they haven’t travelled far. These features include the high indicator mineral count of till samples, the presence of fragile textures (including kelyphite-rimmed garnets and perovskite-mantled ilmenites) and the abundance of fragile species (forsterite olivine and chrome diopside). Majescor also found kimberlite fragments at three different sites. In particular, numerous kimberlite fragments of up to 10 cm in size were discovered at one site containing more than 9,300 indicator mineral grains. Many of the till samples collected within a 300-metre radius of this site contained garnets with kelyphite rims, as well as ilmenites with perovskite mantles. Petrographic analysis on some of the kimberlite fragments confirms they are macrocrystic hypabyssal kimberlite.
Ilmenite and garnet, in particular G9s, dominate the indicator mineral suite in the Wemindji project area, whereas olivine, chromite and chrome diopside are scarcer. According to Majescor, the mineral chemistry of the indicator minerals suggests the kimberlite source has sampled the diamond stability field.
Last fall, Majescor used a small, track-mounted backhoe to dig a series of 39 pits in the area covering two of the known kimberlite float occurrences. The overburden cover is generally thin, extending to a depth of up to 7 metres. Seventy-one samples were collected from the pits, which were dug as deep as 3 metres. The sampled material included glaciomarine sediments at surface, as well as undisturbed basal till at depth.
Based on a minimum indicator count of 300 grains, the pit samples, along with previous surface sampling, defined a 200-to-300-metre-wide dispersion train that extends more than 2 km in length. The indicator train is oriented in the same direction as the most recent glacial movement. The sample with the highest indicator count of 12,350 grains came from the basal till.
Last fall, Majescor drilled six shallow holes without success. The holes all encountered granite. Its petrographic work on the kimberlite fragments suggests the kimberlite is not magnetic. Majescor is now zeroing in on several airborne electromagnetic (EM) anomalies that all lie under shallow lakes or swampy areas. Grid lines were cut over these targets in January, and follow-up ground electromagnetic and gravity surveys were done in preparation for drilling 10-15 of these anomalies, starting in late February.
The Wemindji project was singled out as a prime diamond exploration target in a 2000 report by James Moorhead of the Quebec Ministry of Natural Resources. Moorhead came up with four prospective areas for Quebec diamond exploration by extrapolating a distance of 470 km from known kimberlite fields and using the position of large brittle linear structural zones and their associated cross faults.
Well-situated
The Moorhead report states: “The area between the village of Wemindji and the LG2 hydroelectric reservoir dam is situated at the western end of the Wemindji-Caniapiscau structural zone, which extends from Wemindji, on the eastern shore of James Bay, east-northeast at 70 to the Labrador Trough in the vicinity of Schefferville.
This area is situated at roughly the same distance of 470 km from the three adjacent kimberlite fields: Attawapiskat, Desmaraisville and Otish. It also lies on the northeast projection of the Kapuskasing tectonic zone of Ontario, which hosts numerous alkaline intrusions. This area encompasses an exploration permit of Monopros, which contains a 32-km-long dispersion train of kimberlite indicator minerals.”
Majescor’s own geophysical surveying has identified a strong east-west-oriented structure crossing the property. Described by Norman Paterson of Paterson, Grant & Watson as the Wemindji Extension zone, it is thought to be a major east-northeasterly striking fault that could possibly extend well into James Bay.
In late 2000,
Laval-based
Other juniors with various levels of participation in the Wemindji area include:
Otish Mountains
Majescor is also a major player in the Otish Mountains region. After recovering a single pyrope garnet in each of the two till samples collected during regional exploration for base metals in 1998, Majescor returned to the Otish Mountains the following year and outlined a broad, loosely defined, 25-by-45-km corridor of anomalous kimberlite indicator minerals. This corridor was better defined in 2000 by a further 600 glacial sediment samples.
Once Ashton began staking ground in the Otish Mountains in August 2000, Majescor responded by acquiring 1,028 sq. km of ground covering a large part of the indicator mineral corridor, down-ice from Ashton and Soquem.
The corridor of indicator minerals is dominated by peridotitic garnet (more than 20% are classified as G10s),
followed by picroilmenite. Chromite and chrome diopside are scarce; however, the composition of the chromite falls within the diamond inclusion field. Outside of the immediate Portage dispersion plume, the background is barren of indicator minerals, with less than one positive sample being recorded for every 100 sites (the maximum count in any one sample being one grain).
BHP Billiton Diamonds, a wholly owned subsidiary of
BHP completed an 8,500-line-km airborne geophysical survey, which was followed by ground investigations of some 30 targets, including further till sampling and geophysics. A first pass of drilling will test anywhere between 10 and 20 of these targets.
Microprobe work on the latest till samples indicate that about 30% of the pyrope garnets are G10s, with more than three-quarters of these containing elevated Cr2O3 (in excess of 8% Cr2O3). The chemical composition of the ilmenite and chromite grains also suggests a diamondiferous source. Olivine is abundant, and a few chrome diopsides were recovered in the latest till samples.
Beaver Lake
Ashton and Soquem cannot claim credit for making the first-ever diamond-bearing kimberlite discovery in the Otish Mountains; that honour goes to
Ditem initially tested the kimberlite with six core holes and recovered five macros from 511 kg of sample. The largest stone recovered measured 0.96 by 0.6 by 0.56 mm. However, a follow-up, 7-tonne mini-bulk test sample yielded no diamonds above a 0.8-mm square mesh screen size.
Ditem performed additional work in 1999, consisting of an aeromagnetic survey and limited drilling, resulting in the discovery of lamprophyric material. The junior map-staked 211 sq. km of additional ground in the Techegami River area in the spring 2001 after completing further airborne geophysics.
Pure Gold has also optioned a half-interest in a 164-claim package surrounding the Beaver Lake kimberlite. Under terms of the agreement, Pure Gold must make an immediate payment of $70,000 to Ditem, issue a total 300,000 shares within the year, and spend $500,000 on exploration over the next two years. The partnership has since expanded the Beaver Lake property with additional staking and now holds more than 60 sq. km. An airborne geophysical survey is now being flown over both the Beaver Lake and Techegami holdings.
Ashton and Soquem are not the only companies to hold a sizable chunk of ground in the immediate Beaver Lake area: Majescor carried out widespread reconnaissance sampling in 2001 and identified several anomalous indicator mineral zones in the Mistassini area, less than 5 km west of the Beaver Lake intrusion. The indicator mineral trains are reported to be distinct in terms of chemistry and assemblage from those occurring at Portage, and therefore indicative of a different source.
The indicator mineral suite is dominated by ilmenite, with pyrope garnet and chromite being well-represented. Several G10 garnets have been recovered, as well as diamond inclusion chromite grains (up to 64.2% Cr2O3). The recovery of perovskite-mantled ilmenite suggests a nearby kimberlite source.
Majescor initially staked 1,216 sq. km and intends to stake a further 494 sq. km. The land package stretches from the northern tip of Lake Mistassini to the western limit of the Otish Mountains.
Based on the till sampling results,
Canabrava completed a 7,370-line-km airborne geophysical survey over the property in January. Follow-up ground investigations on those anomalies occurring at the head of each of the distinctive dispersion trains will be followed by drilling.
Iriana Res.
Majescor also farmed out ground to
Topping the list of juniors that have picked up ground in the Otish Mountains is
Other juniors active in the Otish staking rush include:
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