Otish Mountains diamond play heats up

Confirmation that two “kimberlitic” discoveries in the Otish Mountains region of north-central Quebec are diamondiferous has focused attention on the area.

Prior to the Christmas holidays, Ashton Mining of Canada (ACA-T) reported the microdiamond counts from two kimberlitic bodies discovered during a first pass of drilling last fall. A 205.8-kg core sample from Renard 1 yielded 54 micros and 5 macros. (A macro measures greater than 0.5 mm in at least one dimension.) One of the recovered macros exceeds 0.5 mm in two dimensions. Renard 1 was tested with both vertical and angle holes that were collared from the same site. Two holes intersected 98 metres of kimberlitic-type rock before shutting down while still in the unit at 108 metres of depth, owing to budgetary constraints. The Renard 1 geophysical target lies partially on land and partly under water.

The second kimberlitic body, dubbed Renard 2, was discovered 1 km south of Renard 1. It yielded 116 micros and 29 macros from 163.1 kg of sample, including five stones registering 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 was tested by a vertical hole, which intersected 83 metres of kimberlitic material below 18 metres of overburden. The hole was terminated in the kimberlitic unit at a depth of 101 metres. A second hole, drilled from the same site at an angle of minus 60, intersected just 11 metres of kimberlitic rock, starting at 22 metres down-hole, followed by 70 metres of mainly gneiss interspersed with lesser amounts of kimberlitic material.

Two other magnetic anomalies were tested during the first round of drilling and were explained by the presence of magnetite-rich zones in the gneissic bedrock.

When Ashton made the Otish Mountains discoveries, it was cautious in calling them kimberlite, and instead described them as having characteristics consistent with kimberlite. 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 garnet and chromite. A number of the pyropes have high chromium, low-calcium G10 chemical compositions.

Ashton holds more than 1,760 sq. km of mineral permits in the Otish Mountains area in a 50-50 joint venture with Quebec government-owned Soquem. The pair has been searching for diamonds in the northern Quebec portion of the Superior Craton since 1996. After carrying out reconnaissance programs of heavy mineral sampling and airborne magnetic surveys on more than 450,000 sq. km of prospective terrain, the joint venture initially staked 1,000 sq. km of key ground in two areas of Quebec during the second half of 2000. Ashton zeroed in on the Otish Mountains area, 275 km northeast of Chibougamau, and the Caniapiscau region, 500 km east-northeast of Radisson.

Heavy mineral sampling defined several highly anomalous indicator mineral dispersion fans, with some samples containing as many as 1,000 indicator grains, including a high percentage of G10s.

Ashton flew geophysics over the original central Otish Mountains property in late 2000 and followed-up with ground geophysics over eight targets in March 2001. Last summer was spent further investigating these anomalies; 350 heavy mineral samples were taken.

Further work in 2002 will involve delineation drilling on Renard 2 and the collection of a larger test sample, along with heavy mineral sampling and geophysical surveys to define unexplained mineral trains.

Majescor Resources is active in the Otish Mountains area. The junior began ground investigations of regional airborne magnetic anomalies in 1998. Follow-up work in 1999 generated a broad, loosely defined 25-by-45-km corridor of anomalous kimberlite indicator minerals in glacio-fluvial sediments. This corridor was better defined in 2000 by a further 600 till samples.

Once Ashton began staking ground in the Otish Mountains area, Majescor responded by acquiring an initial 1,028 sq. km of ground covering a large part of indicator mineral anomaly, down-ice from Ashton.

BHP Diamonds, a wholly owned subsidiary of BHP Billiton (BHP-N), struck a deal with Majescor this past summer to earn up to a 56% interest in the Portage property block by funding all costs through to production. BHP completed an 8,500-line-km airborne geophysical survey, which was followed by ground investigations of selected targets, including further till sampling. Ground geophysics will be carried out in order to outline targets in preparation for drilling.

Uranerz Explorations & Mining previously discovered a kimberlite body in the Otish Mountains region during the late 1970s while exploring for uranium. The diamondiferous Beaver Lake kimberlite lies 50 km south of Ashton’s property package. Ditem Explorations (DIT-V) entered into an option agreement with Uranerz in 1998 and can earn a 49% interest in the Beaver Lake property by spending $1.5 million over four years.

Ditem initially tested the kimberlite with six core holes in 1998 and recovered four macros from selected samples weighing 96.1 kg. However, a follow-up, 7-tonne test sample yielded no diamonds above a 0.8-mm square mesh screen size.

In 2001, Majescor carried out widespread reconnaissance sampling and identified several anomalous indicator mineral zones in the Mistassini area, less than 5 km west of the Beaver Lake kimberlite. Majescor staked 1,216 sq. km in this area, with a further 494 sq. km still pending approval by the Quebec Ministry of Natural Resources. 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 Diamond (CNB-V) entered into an option agreement with Majescor on the Mistassini package, and can earn a half-interest by spending $1.3 million on exploration and issuing 100,000 shares over three years. A 7,370-line-km airborne geophysical survey over the property began mid-December as a prelude to possible drilling in early 2002.

Majescor recently farmed out ground to Iriana Resources (IR-T), which can earn a half-interest in four separate properties covering 250 sq. km by spending $750,000 over three years. The property package is near the main Majescor-BHP block.

Other juniors that have recently picked up ground in the Otish Mountains area include: Dios Exploration, a soon-to-be-listed diamond vehicle of Sirios Resources (SOL-V), Melkior Resources (MKR-V), Plexmar Resources (PLE-V), Canalaska Ventures (CVV-V), Boulder Mining (YBR-V) and New Blue Ribbon Resources (NBL-V).