De Beers’ Canadian exploration division has targeted the Slave Craton of the Northwest Territories and Nunavut, as well as the Superior Craton, which covers parts of Manitoba, Ontario and Quebec. Its 20 or so active projects range from early-stage grassroots to its most advanced-stage undertaking, the Snap Lake dyke underground diamond project in the Northwest Territories.
Snap Lake is 220 km northeast of Yellowknife and 110 km south of the Ekati diamond mine. De Beers Canada Mining filed an environmental assessment (EA) for the project with the Mackenzie Valley Environmental Impact Review (EIR) Board in February.
The EA is a comprehensive report on proposed mining methods and management of environmental issues. The report also covers the project’s socio-economic impact.
De Beers proposes developing a 3,000-tonne-per-day underground diamond mine and kimberlite processing plant with an operating life of 22 years. The Snap Lake dyke contains indicated reserves of 22.8 million tonnes at a minable grade of 1.65 carats per tonne, equivalent to 37.6 million carats at a present value of US$90 per carat, or US$148 per tonne. A further 20 million tonnes are categorized as inferred. Annual production is pegged at 1.9 million carats.
While the Mackenzie Valley EIR Board reviews the Snap Lake environmental assessment, De Beers will hold a series of public meetings in Territorial communities to discuss the report. The Snap Lake team will also begin negotiating participation agreements with aboriginal groups, which have traditionally used the land around Snap Lake.
De Beers expects the Mackenzie Valley EIR Board should be in a position to makes its recommendations to the federal minister of Indian and Northern Affairs by the end of the third quarter. The project would then move to the licensing phase under the Mackenzie Valley Land and Water Board. De Beers anticipates all necessary permits and regulatory approvals will be received in 2003.
Subject to final approval by De Beers’ board of directors, underground development will resume in 2003, with construction in full swing in 2004, leading to startup in late 2005 and full production in the first half of 2006. The project will employ roughly 400 people during construction and create upwards of 450 permanent positions.
De Beers operates 20 diamond mines in South Africa, Botswana, Tanzania and Namibia. Some are wholly owned, whereas others are joint ventures with governments. Its operations produced some 39 million carats in 2001. Snap Lake will be De Beers’ first mine outside of southern Africa.
Faced with complex geology and a highly variable diamond grade, De Beers began prefeasibility work this winter on the Victor project in the James Bay Lowlands of northern Ontario. The study is expected to take about 12 months to complete.
The Victor kimberlite occurs in a cluster of 19 pipes, 90 km west of the coastal community of Attawapiskat on the western side of James Bay. De Beers discovered 16 of these bodies as a result of drilling in 1988 and 1989. More than 100 kg of core from each of the kimberlites was initially analyzed for microdiamonds, and all but one proved to be diamondiferous.
Subsequently, in 1994, two additional small kimberlites, dubbed MacFayden No. 1 and No. 2, were discovered by
Last year,
The Attawapiskat kimberlites occur in the Moose River Basin along the southern flank of the Cape Henrietta Maria Arch. The kimberlites were emplaced during the Jurassic period, between 155 and 180 million years ago. The Victor kimberlite is the largest body in the cluster, comprising one large Main pipe and a smaller, Southwest pipe. The two pipes nearly coalesce at surface and together cover a surface area of 17 hectares.
The Victor kimberlite is covered by at least six metres of glacial and marine till and is emplaced into 275 metres of Paleozoic sediments, which overlie Archean basement. The observed sediments consist predominantly of Ordovician-Silurian limestones and dolomites, with some shales, siltstones and sandstones. Evidence suggests the pipes have been significantly eroded.
At the recent convention of the Prospectors & Developers Association of Canada, in Toronto, Victor project manager Brad Wood spoke about the company’s exploration history in the Attawapiskat area. Although De Beers first targeted the James Bay region for its diamond potential in the early 1960s, it wasn’t until a 1984-1986 regional stream sediment sampling program between the Kenogami and Ekwan Rivers that a distinct kimberlite indicator mineral train began to be detected, emanating from the Attawapiskat region.
An indicator mineral population that included garnet, ilmenite, clinopyroxene and spinel grains were recovered from rivers flowing south of the Ekwan River. The garnets were mainly peridotitic, falling into the G9 classification, with less common G10 varieties. Kimberlite boulders were discovered in 1987 along a 10-km stretch of the Attawapiskat River, where stream samples were found to contain “super abundant” concentrations of indicator mineral grains. De Beers followed with an aeromagnetic survey, using both magnetic field and vertical magnetic gradient measurements, to cover 2,900 sq. km. Thirty-three anomalies were further defined with ground magnetics. Drilling in 1988 and 1989 confirmed 16 kimberlite bodies.
The initial microdiamond results were not especially encouraging, says Wood, and so De Beers shifted its focus to the Northwest Territories. In 1997, De Beers revisited the Attawapiskat area and collected small test samples using a portable reverse-circulation (RC) rig.
“The results of that were encouraging enough to go back in 1998 and 1999 and extract 600 tonnes from Victor using trenching and larger-diameter RC drilling,” Wood says.
At a public information session held in the spring of 2000 at Attawapiskat, De Beers representatives revealed that a 330-tonne bulk sample collected in 1999 yielded 107.9 carats of diamonds with a value of US$16,590. The results implied a preliminary grade of 0.32 carat per tonne, a diamond value of US$155 per carat, and a kimberlite value of US$50 per tonne.
An advanced exploration program started in November 1999 with the drilling of a series of core holes to provide a better understanding of the size, shape and internal geology of the Victor kimberlite prior to the commencement of bulk sampling. An 80-man exploration camp and modular dense media separation processing plant were constructed at the time. News that De Beers was undertaking bulk sampling on the Victor pipe sparked renewed interest in the potential of the Superior Craton.
In early 2000, about 5,350 tonnes of kimberlite were extracted from two large surface trenches on the Main and Southwest pipes, while a further 1,168 tonnes were collected from large-diameter RC holes drilled to a depth of up to 200 metres. In total, 2,944 carats of diamonds were recovered from 6,262 tonnes of kimberlite, giving an implied grade of 0.
47 carat per tonne.
Further bulk-sample drilling was conducted on the Victor pipes in the first quarter of 2001. An additional 570 carats were recovered from 1,800 tonnes of kimberlite gathered from 28 holes. In total, some 8,392 tonnes of kimberlite collected from Victor have yielded 3,622 carats for an implied grade of 0.43 carat per tonne.
Wood says De Beers has evaluated some 9,560 tonnes of kimberlite collected from the two large surface trenches and some 37 large-diameter RC holes drilled to a maximum depth of 250 metres. The large-diameter drilling is an important component of the program, explains Wood. “It gives a more spatial distribution of the diamond grade in the deposit.”
Down-hole geophysics is done on all large-diameter RC holes. This information is primarily used for calculating accurate sample masses for grade estimates, and is also useful in areas where the geological boundaries may be difficult to identify.
“There are still large areas of kimberlite that have yet to be drilled,” Wood adds. “We have also recently drilled some kimberlite to the southeast, which we have yet to explore for diamonds.”
De Beers estimates Victor Main contains an inferred resource of 22.8 million tonnes of kimberlite, whereas Victor Southwest hosts about 13.3 million tonnes, for a total of 36.2 million tonnes.
The geology of the Victor deposit is complex. Victor Main contains some hypabyssal kimberlite in the northern portion, whereas the remainder is pyroclastic in nature. Wood explains: “There have been several intrusions, which have formed the craters, and each of these intrusions has a variable diamond grade. Even within some of the intrusions, there seems to be a variation in the diamond grade, which makes revenue resource modeling of the deposit difficult.”
De Beers has established a $100-per-tonne value for Victor.
In November 2001, De Beers unveiled the results of a desktop or scoping-style study that identified a host of geotechnical hurdles the project needs to clear before a production decision can be made. Water management, ground water disposal and treatment, site access and logistics, and project costs are all issues that need to be addressed. The entire project area is covered by muskeg and extremely wet.
Current plans call for drilling program to enhance understanding of the geotechnical nature of the underlying clays, overburden, country rock and the hydrology around any future open-pit operation. Wood says there are concerns over the stability of an open-pit mine slope.
Seismic and electromagnetic surveys will be conducted, and civil engineering tests will include the construction of trial structures on top of the muskeg. Three drill rigs are employed on-site. De Beers is also investigating measures to determine capital and working costs as part of the prefeasibility study, and the formal environmental assessment and permitting process will be initiated.
“We will be looking at many different aspects of developing a mine on the site,” says Wood. “We’re hoping it will be one of the first diamond mines in Ontario.”
Spider
A further 150 km west of the Attawapiskat cluster, De Beers is set to drill eight kimberlite targets in a 70-by-120-km area under option from Spider Resources and KWG.
The area, known as the Spider 3 project, lies west of the five Kyle Lake kimberlitic bodies. Spider and KWG discovered the deep-seated Kyle Lake series between 1994 and 1996.
The Kyle Lake series of intrusive bodies is much older than the Attawapiskat cluster and is age-dated at 1.1-1.2 billion years.
The Kyle Lake 1 body was discovered in 1994, about 100 km southwest of the Attawapiskat cluster, using aeromagnetic geophysical data. Kyle Lake 1 is covered by up to 135 metres of Paleozoic sediments and overburden. Spider and KWG estimate that Kyle Lake 1 has a surface area of 2.6 hectares and contains some 14.5 million tonnes of “kimberlite” to the 510-metre level, based on 18 holes. In all, 6.2 tonnes of sampled core yielded 3,602 micros and 793 macros for a combined total weight of 3.71 carats.
There is some confusion as to whether the Kyle bodies are true kimberlites. Several specialists have examined the core and offered differing opinions. Roger Mitchell stated it was not kimberlite but probably some form of a lamprophyre; Glen Sinclair suggested the intrusion is a hybrid, falling somewhere between an alnoite and a kimberlite; whereas Barbara Scott-Smith pondered on the likelihood that the surrounding granite gneissic terrain had contaminated the original kimberlite intrusion.
Studies by De Beers on a small representative sample of 111 macros recovered from Kyle Lake 1 indicate a wide variation in colour, morphology, resorption, nitrogen content and aggregation state. The results support the theory that Kyle Lake 1 is a multi-phase kimberlite.
The diamonds that were evaluated were between 0.8 and 2 mm in at least one dimension and dominantly octahedral in morphology, with minor resorption. About 64% of the diamonds are colourless, whereas a smaller portion consists of yellow-brown stones. Low-nitrogen and nitrogen-free diamonds are most common. The abundance of these two types is consistent with a peridotitic mantle source, with minor sampling of eclogitic material.
Spider and KWG are awaiting the micro results of further core drilling completed a year ago on the Kyle Lake 3 kimberlite. Discovered in 1995, Kyle Lake 3 is 100 km northwest of Kyle Lake 1 and 120 km due west of the Victor kimberlite.
The Kyle Lake 3 body is believed to be a complex, multi-phase diatreme intrusion, with numerous dykes emanating from it in all directions. One particular east-west-striking dyke has an elevated diamond count; it extends 450 metres along strike, with a near vertical dip and an average width of 25 metres. Twenty-one holes have tested this dyke-like body. To date, the processing of 2,045 kg of sampled core from 15 holes has yielded 1,517 micros, including 100 stones greater than a 0.425-mm square-mesh screen size.
The Spider 3 project area was previously explored for its diamond potential by Spider and KWG from 1995 to 1997. The pair spent a total of $1.4 million carrying out regional mapping and sampling, in addition to flying a widely spaced low-level aeromagnetic survey.
In April 2000, De Beers signed a confidentiality agreement with the pair and undertook a due diligence investigation that identified more than 20 priority targets. Before signing a definitive option agreement in March 2001, De Beers staked those targets and created the property base for the joint venture.
De Beers can earn an initial half-interest in the Spider 3 claims by spending $1.5 million before mid-April 2003. An additional 10% can be acquired by spending a further $4 million over the following four years.
De Beers has upgraded eight of the priority targets to drill-ready status following further airborne and ground geophysical surveys, along with geochemical sampling. Another six targets will be further defined with ground geophysics.
Dumont Nickel
Several juniors are active in the Superior Craton of northern Ontario.
Canabrava Diamond resumed drilling of 15 planned targets in mid-February at the Groundhog project, which covers an area of interest extending from the eastern shores of Lake Superior north to Kapuskasing. Ownership of the project is split between by Canabrava, with 64%, and
Using the results of its own heavy mineral sampling and airborne geophysical programs, together with the results of programs funded by the Ontario government,
in northern Ontario that cover more than 200 individual geophysical features.
Regional till and stream-sediment sampling programs uncovered garnets, diamond inclusion chromites, ilmenite and chrome diopside. Follow-up prospecting on selected airborne geophysical anomalies resulted in the discovery of two kimberlite dykes and float material.
Ground geophysical surveys are under way over 49 of the airborne anomalies. The remaining airborne targets will be tested over the course of the year. Heavy mineral sampling will begin in late May, following spring breakup.
De Beers has several other advanced projects in Canada, including the Gahcho Kue (formerly known as Kennady Lake) joint venture in the Northwest Territories, where another $10 million is being spent this winter to collect additional bulk samples.
Gahcho Kue comprises a portion of the AK/CJ claims, held 51% by De Beers Canada Exploration, 44.1% by
This year’s work will involve drilling 4-5 large-diameter drill holes into each of the 5034 and Hearne kimberlites to recover another 2,000 carats. The objective is to increase the confidence and accuracy of the revenue model for the project, based on enhanced understanding of diamond size and frequency distribution characteristics.
De Beers tabled a desktop study of Gahcho Kue in 2000 that fell short of the critical mass to achieve the 15% rate of return required to proceed to feasibility. Last winter, De Beers targeted the 5034 and Hearne pipes for further bulk-sampling. The major wanted to recover a larger number of diamonds to increase the confidence level of its desktop study. The 2001 bulk sample drilling yielded an additional 1,665 carats using a 1.5-mm cutoff, bringing to 3,491 carats the total parcel recovered from the two pipes. However, the newly modeled carat values, based on a diamond parcel nearly twice the previous size, were down 5% for 5034 at US$65.50, and down 11% for Hearne at US$63.30.
Despite the lower values, which are consistent with the drop in the value of the rough diamond market, De Beers is back at Gahcho Kue this year trying to make the project work. The decision was based on the recovery of a 9.9-carat, gem-quality stone from the 5034 pipe that was valued at US$60,000, or US$6,000 per carat. De Beers believes there may be a statistically significant population of high-quality diamonds present in the 5034 and Hearne pipes.
The 2002 bulk sample results will be used to update the existing desktop study, which will determine the project’s future. The study proposed open-pit mining for the 5034 and Hearne pipes, along with a high-grade zone within the top 140 metres of Tuzo pipe. The 5034 pipe contains a modeled resource of 12.5 million tonnes grading 1.64 carats per tonne at US$107 per tonne.
The Hearne pipe hosts 7.2 million tonnes grading 1.71 carats per tonne, or US$108 per tonne rock, whereas the higher-grade zone in the Tuzo pipe contains a modeled 1 million tonnes grading 2.7 carats per tonne at US$43 per carat, based on the 1999 bulk sample.
In Saskatchewan last fall, De Beers and joint-venture partners
The program was designed to evaluate and improve the confidence levels on ore-value models for kimberlite body 141, and to gain a better indication of macros in kimberlite 150. In addition, kimberlite bodies 141, 140 and 150 were further delineated with 16 core holes.
The Fort la Corne property is 65 east of Prince Albert and covers 121 claims totalling 225 sq. km. Sixty-three kimberlite bodies are held by the joint venture. De Beers is the operator of the project, with a 42.3% stake. Kensington owns an equal percentage, whereas Cameco holds 5.5% and UEM is carried with a 10% stake.
In 2000, De Beers reviewed all the diamond results to that time and assessed five kimberlites on the basis of diamond size distribution, grade and tonnage. Two kimberlite bodies, 122 and 141, were chosen for further evaluation through large-diameter drilling. The 122 body is estimated to contain in excess of 540 million tonnes of kimberlite, whereas 141 was thought to host 395 million tonnes. However, based on the results of the 2001 delineation drilling, kimberlite bodies 140 and 141 are now believed to form a single body containing 932 million tonnes. The Fort la Corne kimberlites lie beneath 75-150 metres of cover and have no surface expression.
The 328-tonne drill sample collected from kimberlite 122 in 2000 yielded 212 diamonds greater than 1 mm, and these weighed 17.31 carats. Based on combined size distributions of micros and macros, De Beers modeled a grade for kimberlite 122 within a range of 7.5 and 12 carats per 100 tonnes. The “best-fit” model averaged an impressive value of US$144 per carat, with a corresponding revenue estimate of US$11 per tonne.
In total, 278 diamonds weighing 21.06 carats were recovered from 251.8 tonnes of sample from kimberlite 141 in 2000. Eight stones were larger than half a carat, with the two largest stones weighing 1.53 and 1.08 carats. De Beers has modeled a grade of 18 carats per 100 tonnes for the 141 pipe, with a best-fit value of US$153 per carat, or US$28 per tonne.
Last fall, De Beers recovered a further 768.8 tonnes of kimberlite from nine large-diameter holes into kimberlite 141 and an initial 121 tonnes from one hole into body 150. Diamond recovery and valuation results are expected shortly.
De Beers holds several other joint ventures in Canada, including the Knife project, with
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