More kimberlites found at Churchill

The discovery of two more kimberlites during a first pass of drilling on the Churchill project, north of Rankin Inlet in Nunavut, brings the total number of kimberlite bodies found to date to seven.

Shear Minerals (SRM-V) and Northern Empire Minerals (NEM-V) have drilled nine circular geophysical features as part of a program designed to test at least 15 targets.

The joint-venture partners have recorded only two misses so far, including one hole that ended short of its target as a result of drilling problems caused by almost 40 metres of deep, bouldery overburden. “We still haven’t properly evaluated that target,” Shear President Pamela Strand tells The Northern Miner. The overburden cover at Churchill is typically anywhere from 6 to 17 metres thick. The second miss was explained by iron formation in the drill core.

Six of the kimberlite discoveries (Qaumallak and Kalluk 1-5) occur in a 12-by-12-km area. The most recent kimberlite find, Tuvaaq 1, is a further 9 km to the northeast. Tuvaaq 1 is a magnetic high, with a coinciding electromagnetic (EM) signature, measuring 125 metres in diameter. Kimberlite was encountered at a depth of 15 metres.

The holes are all vertically drilled and range from 65 to 106 metres in total depth. Strand says some of the holes have ended in kimberlite, while some have not. Shear intercepted 53 metres of kimberlite while drilling Kalluk 5 before ending in country rock at a depth of 106 metres. The Kalluk 5 discovery was not on the original list of priority targets; it was added after ground crews completed infill grid geophysical surveys before leaving the area. “This was obviously a beautiful mag target so we drilled it,” Strand says.

With just one hole drilled into each body, Strand is convinced these new discoveries are pipes based on the geophysical signature and the kimberlite textures that her field personnel are observing in the drill core. The kimberlites show evidence of multi-phases, including:

— olivine-ilmenite macrocrystic magmatic facies, with occasional juvenile lapilli;

— heterolithic tuffisitic kimberlite breccia, with crustal xenoliths, kimberlite autoliths and/or juvenile lapilli; and

— olivine macrocrystic hypabyssal kimberlite.

Some of these phases are suggestive of crater and diatreme facies, which are unique to a pipe setting, says Strand.

Shear is the operator of the Churchill project, with a 51% stake. Northern Empire is earning a 35% interest by contributing $750,000 to exploration, and the remaining 14% is held by BHP Billiton (BHP-N).

“The drilling has far surpassed our expectations,” says Strand. “We are all extremely excited. Success this early on in a project is phenomenal. We are in a long-term exploration project, but with [till] indicator mineral chemistry like we have, it’s just a matter of time before we find the source of the G10s.”

The 4,164-sq.-km project extends more than 100 km inland from the western shores of Hudson Bay, north of Rankin Inlet. The Churchill joint venture has farmed out an adjoining, 1,550-sq.-km package of ground to International Samuel Exploration (SAZ-V), which can earn up to a 65% interest by spending $1 million on exploration over two years. Shear and Northern Empire retain the right to buy back a 10% interest for $100,000, which would leave Samuel with 55%, Shear with 23%, Northern Empire with 16%, and BHP Billiton with 6%.

During 2001 and 2002, APEX Geoscience of Edmonton carried out regional till sampling on behalf of Shear and discovered two separate occurrences of kimberlite float. In total, 145 microprobe confirmed kimberlite indicator mineral grains were recovered from 183 till samples.

Last fall, a high-resolution airborne magnetic survey totalling 16,307 line km revealed 226 anomalies. This spring, ground magnetics and horizontal-loop electromagnetics were conducted over 31 anomalies, further defining 23 drill targets. Drilling got under way in June, with some 15 targets originally scheduled for testing. Strand now believes as many as 19 targets could be drilled during the first pass. “We’re adding targets as we go,” she says. Drilling is currently focused on a new cluster of magnetic anomalies 20 km away from kimberlite discoveries.

Samples from the first five kimberlites are ready to be shipped to the Saskatchewan Research Council for microdiamond analysis, but it could be a lengthy wait. The Churchill partners are in line behind Cumberland Resources (CBD-T) and Comaplex Minerals (CMF-T), which recently wrapped up drilling on their neighbouring Meliadine East project by intersecting kimberlite on all but one of the 12 circular geophysical targets tested.