Churchill kimberlite camp proves frustrating

Despite disappointing microdiamond results from a second year of drilling on the Churchill joint venture in eastern Nunavut, Shear Minerals (SRM-V) and Stornoway Diamond (SWY-V) continue to promote the project’s potential, based on the promising chemistry of G10 pyrope garnets recovered in till samples.

Of the six new kimberlites discovered by Shear during a fall drilling campaign, one is weakly diamondiferous while the other five are barren.

A 164-kg sample from discovery KD-428 yielded just three small microdiamonds no bigger than a 0.15-mm square sieve classification.

This year’s program tested various geophysical targets in distinct corridors where “high-interest” indicator minerals have been recovered in till samples. Shear managed to drill 11 geophysical targets in the main Josephine River corridor before being chased out by deteriorating weather conditions this past autumn. The company intends to return next spring for further drilling, which will test upwards of 30 targets.

“We’re confident we will be able to track the G10 chemistry back to diamondiferous kimberlites in the coming year,” says Shear Minerals President Pamela Strand. Since 2001, more than 2,700 kimberlite indicator mineral grains have been picked from 738 of the 1,942 till samples processed. About 27% of all recovered pyrope garnets display promising G10 sub-calcic composition, bearing favourable diamond-inclusion chemistry.

Says Stornoway President Eira Thomas: “The source of the high-interest mineral chemistry at Churchill remains elusive, but we have made great progress in advancing our knowledge of this prospective area and remain optimistic that results from the 2004 till sampling campaign will help us narrow our search and increase our chances of success in 2005.”

Last year, Shear and joint-venture partners Stornoway and BHP Billiton (BHP-N) drilled 24 geophysical pipe-like targets, which were supported by limited till sampling data. In the process, they discovered 18 new kimberlites scattered across a 60-by-60-km-wide area on the Churchill claims, including two at Churchill West, an adjoining property under option to International Samuel Exploraton (SAZ-V). Ten of the kimberlites proved to be weakly diamondiferous; samples from the other eight were barren.

The best results of the 2003 season came from the first discovery, known as Quamalak-1, or target CK-151. A 158-kg sample of kimberlite core held eight small microdiamonds no larger than a 0.425-mm square sieve upper cutoff. The three largest stones measure 0.6 by 0.56 by 0.48 mm, 0.48 by 0.4 by 0.36 mm, and 0.24 by 0.4 by 0.3 mm. These three small stones have the distinction of being the largest diamonds recovered from any of the kimberlites discovered to date in the Churchill camp.

The microdiamond counts and stone size at Churchill are comparable to what Cumberland Resources (CLG-T) and Comaplex Minerals (CMF-T) turned up on their neighbouring Meliadine East project, where all but one of 12 circular anomalies drilled in the spring of 2003 proved to be kimberlite. The discoveries at Meliadine East proved disappointing as only one kimberlite body was diamond-bearing, albeit weakly, returning just three small microdiamonds measuring less than a 0.212-mm square-mesh screen from a 32-kg representative sample.

Centred 20 km north of Rankin Inlet and covering 333 sq. km along the eastern half of a highly prospective gold belt, Meliadine East has been the focus of gold exploration by Cumberland and Comaplex through a 50-50 joint venture since 1993. Despite encountering several narrow kimberlite and ultrapotassic dykes while drilling gold targets, Cumberland and Comaplex only began assessing the project’s diamond potential in 2001, after receiving the results of a regional airborne survey flown over the Meliadine belt by WMC Resources of Australia. A review of the magnetic data showed a cluster of discrete anomalous targets.

In the early summer of 2002, regional till sampling was conducted in areas down-ice of the circular geophysical features. Of the 82 samples collected, 64 contained at least one kimberlite indicator mineral grain, and 19 samples had multiple grains. The latter samples contained 155 of the 234 indicator mineral grains recovered, including various combinations of olivine, ilmenite, garnet and chromite.

In total, eight pyrope garnets were found in seven samples, two of which had significant diamond-associated, sub-calcic G10 compositions. Eleven of 18 recovered chromite grains were classified as kimberlitic, with one grain bearing diamond-inclusion-type chemistry.

Cumberland re-flew the area in the fall of 2002 with a 4,000-line-km aeromagnetic survey, confirming the mag signatures of more than 25 obvious circular features. A $725,000 drilling campaign in the spring of 2003 tested 12 of the magnetic anomalies with 16 holes, resulting in 11 kimberlite discoveries. Representative composite drill core samples ranging from 32 to 48 kg in weight were collected from each of the bodies for microdiamond analysis. Nine of the kimberlites were found to contain no diamonds larger than a 0.106-mm square-mesh bottom-size cutoff.

Churchill

Shear Minerals is the operator and owner of a 51% interest in the Churchill project, with Stornoway holding 35% and BHP Billiton, 14%. In February 2004, the joint-venture partners acquired a further 6.4 million acres, or 25,900 sq. km, of prospecting permits surrounding and adjoining the Churchill project. The joint venture’s landholdings now encompass 34,000 sq. km, or 8.5 million acres.

International Samuel can earn into a 65% interest on the adjoining 2,080-sq.-km Churchill West project by spending $1 million on exploration over two years. Once Samuel has vested, the Churchill joint venture will have the right to buy back 10% for $100,000 cash.

Shear first established the Churchill joint venture with the Hunter Exploration Group in June 2001 as a conceptual play. (The Hunter group retains a 2% gross overriding royalty on the project after optioning a 35% position to Stornoway in 2002 and selling its remaining 14% stake to BHP in 2003 for $3 million cash.) The pair felt the area justified further investigation for diamonds, given its cratonic setting, favourable regional structure, and the known presence of kimberlite dykes. The Geological Survey of Canada (GSC) had conducted a surficial mapping program of the Meliadine trend from 1997 to 1999 and, in the process, collected 220 regional till samples at an average sample spacing of 4 km. Based on the results of the till sampling, a 2000 GSC report by McMartin suggests that the potential for kimberlite in outcrop, kimberlite float, and kimberlite indicator minerals exist throughout the area.

Under the supervision of Edmonton-based APEX Geoscience, 48 regional till and beach sand samples were collected in September 2001, from which 25 kimberlite indicator mineral grains were recovered from 19 samples. This work led the partners to acquire more than 2,185 sq. km of contiguous mineral claims and exploration permits pertaining to the Churchill project.

Microprobe analysis by R.L. Barnett Geological Consulting confirmed the recovery of half-a-dozen subcalcic G10 garnets bearing promising diamond inclusion chemistry, as well as eight G9 garnets, one eclogitic garnet, six chrome diopsides and five olivine grains.

During the summer of 2002, a high-resolution airborne magnetic survey totalling 16,307 line km was flown over the area, revealing 226 anomalies of interest. That summer, two separate occurrences of kimberlite float were discovered by field crews who were out collecting an additional 135 regional till samples. In total, 120 indicator mineral grains were found in 30 of the samples. One sample contained 45 pyrope garnets and two eclogitic garnets. Again, a high proportion of the pyrope garnets exhibit G10 sub-calcic composition with favourable diamond-inclusion chemistry.

Based on the results of the 2002 field program, the joint venture more th
an doubled its land position at Churchill heading into 2003. Ground magnetics and horizontal-loop electromagnetics were conducted on 72 airborne targets in preparation for drilling in the summer of 2003, when 24 targets were tested and 18 kimberlites discovered. “The 2003 drill program was designed to test high-confidence geophysical targets with limited support from regional geochemical data,” states Shear in its 2004 annual report. “Exploration in 2004 will benefit from expanded geophysical coverage and a more extensive geochemical data set, which was collected but not available during the 2003 drilling campaign.”

During the 2003 exploration season, Shear extended the airborne magnetic coverage to the north with fixed-wing surveys totalling more than 34,000 line km. The new magnetic coverage revealed 483 anomalies of interest. In addition, Shear dramatically increased the sample density of the project area by taking a further 1,603 till samples on the Churchill portion and 279 tills on the Churchill West option. The results were used to direct the 2004 program, which saw an additional 4,213 till samples collected. In addition, a high-resolution helicopter-borne magnetic and electromagnetic survey totalling 33,600 line km was flown over the expanded project area. A preliminary interpretation of the data has identified a staggering 1,500 targets of interest.

Indicator minerals

Elsewhere in eastern Nunavut, Indicator Minerals (IME-V) has entered into option agreements covering 7 million acres (28,000 sq. km). The junior, led by Bruce Counts, initially struck a deal with the Hunter Group to acquire an 80% stake in more than 12,100 sq. km of prospecting permits and mineral claims, near the communities of Kugaaruk and Taloyoak. The properties are in the Committee Bay area, Boothia Peninsula, and the Chesterfield Inlet area. Reconnaissance sampling in the summer of 2003 produced several samples containing high-interest kimberlite indicator minerals, such as lherzolitic garnet, manganese ilmenite, chrome diopsides, chromite and olivine.

Indicator has entered into an agreement with the Hunter group of companies whereby it has the exclusive right to acquire an 80% interest in any additional diamond projects identified by the privately led staking syndicate.

Indicator has been studying the roughly 2,000 till samples taken on the 2,800-sq.-km area known as Kugaaruk.

Indicator can also earn a 70% interest in the diamond rights to more than 12,100 sq. km of land held by Committee Bay Resources (CBR-V) in Nunavut. By spending $3 million on exploration before the end of 2006, Indicator can initially earn a half-interest. An additional 20% can be had by spending another $2 million in the following year. Indicator Minerals and Committee Bay share common directors and management.

Indicator also holds ground jointly with International Samuel, specifically 5,600 sq. km immediately west of Dunsmuir Ventures‘ (DVV-V) Nanuq project, southwest of Wager Bay. The project area, in which each company has a 40% interest, was staked based on promising results from regional indicator mineral sampling carried out by the Hunter group, which holds the remaining 20%. The Hunter group recently staked an additional 138 sq. km adjacent to the northern boundary of the Nanuq project, after the area became open for exploration. The area had been temporarily withdrawn from mineral exploration by an “order in council” concerning the proposed Ukkusiksalik (Wager Bay) National Park.

Dunsmuir, which is preparing to merge with Eric Friedland’s privately held Peregrine Diamonds, outlined a highly promising 36-km-long indicator mineral train that extends toward the northeastern property boundary. This spring, Dunsmuir drilled five promising geophysical targets at the head of this anomalous corridor without intersecting any kimberlite. A summer field program involved the collection of an additional 501 till samples from the heads of both the main and southwestern mineral dispersion trains. In addition, an airborne gravity and magnetic survey covering 7,500 line km was flown across a portion of the Nanuq project using BHP Billiton’s proprietary Falcon system.

Under the amended terms of a merger arrangement, Dunsmuir shareholders will receive one share of the new Peregrine Diamonds for every seven shares held. Peregrine shareholders will still receive one share of the new Peregrine Diamonds on a 1-for-1 basis. The companies have penciled-in extraordinary general meetings for shareholder approval in mid-January 2005.

Peregrine recently optioned three separate properties in the Western Churchill geologic province of Nunavut from BHP Billiton Diamonds, based on the results of anomalous regional heavy-mineral sampling. The Dubwant Lake, Tulemalu and Area 2 properties cover 13,440 sq. km in total. Peregrine can earn an initial 65% stake in the three properties by completing a $1-million till sampling and prospecting program by mid-October 2005, and a further 35% by spending an additional $800,000 before the end of next year. BHP Billiton retains a back-in right for up to a 65% interest.

Dunsmuir personnel completed heavy mineral sampling on the three properties before the end of this year’s field season.