Ekati Diamond Mine, North-West Territories, Canada
Ekati diamond mine, near Lac de Gras in Canada's North-West Territories, is about 300km north-east of Yellowknife. The mine is owned by Dominion Diamond Corporation (DDC), and Archon Minerals.
DDC acquired the mine from BHP Billiton in April 2013 for $553m, and currently holds 88.89% interest in the Core Zone and 65.3% in the Buffer Zone of the mine.
Ekati is Canada's first surface and underground diamond mine. It was discovered in 1991 and formally commenced diamond production in October 1998. It achieved the one million tonne production milestone by 1999. A 78ct diamond was discovered at the mine in late 2010. It was the first time in 12 years of production that a diamond of such a significant gem quality was discovered at Ekati.
The mine's production crossed 50 million carats of diamonds in 2011. Ekati has a current mine-life up to 2019.
Ekati diamond mine geology and reserves
The Ekati kimberlite pipes are part of the Lac de Gras kimberlites, which are similar to those of South Africa and Russia, with all the kimberlite pipes being overlain by small lakes. The kimberlites intrude both granitoids and metasediments and are mostly associated with dykes and lineaments.
The kimberlite pipes extend to a depth of 400m to 600m below the current land surface. Fault zones, fault intersections and dyke swarms control the distribution of kimberlites. Fine-grained sediments are categorised as xenoliths and the disaggregated material indicates the existence of sedimentary cover during kimberlite emplacement.
The pipe infill at Ekati is classified into six rock types - magmatic kimberlite, tuffisitic kimberlite, primary volcaniclastic kimberlite, olivine-rich volcaniclastic kimberlite, mud-rich, resedimented volcaniclastic kimberlite (RVK), and kimberlitic sediments.
Olivine-rich re-sedimented volcaniclastic and primary volcaniclastic types of mineralisation is pre-dominantly found at Ekati.
The proven and probable reserves of Ekati mine as of 31 January 2014 are estimated to be 17Mt containing 18.8 million carats grading at 1.1 carat per tonne.
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Ekati mine plan and details
To date, 150 kimberlite bodies have been discovered within the project's concession area, although most of these do not carry economic diamond concentrations. The mining plan focused mainly on open-pit mining from the Panda, Koala, Fox, Beartooth, Pigeon, Sable and Misery orebodies, with subsequent underground production from Panda and Koala.
Open-pit mining started on the Panda pipe and Koala, Misery and Fox pipes were sequentially developed, some 35-40Mtpa of waste rock excavated from the pits. The ore is processed at the 18,000t/d-capacity processing plant. The 3.4km Panda Diversion Channel diverts water around the Panda and Koala Lakes into Kodiak Lake.
Open pit operations at the Koala mine ended in 2007, while the underground operation, which began in 2007, is currently active. Mining operations at the Misery mine were completed in 2006 and pre-stripping works for a second phase are currently undertaken, with production expected to start in 2016.
The proposed Jay kimberlite pipe (Jay Project) is expected to add 10 to 20 more years of production life to Ekati. The Developer's Assessment Report (DAR) was submitted to the Mackenzie Valley Environmental Impact Review Board in November 2014.
Mining equipment includes four Driltech D90KS blasthole drills, two Demag H655SO diesel-hydraulic shovels, ten Caterpillar D10R bulldozers, a Cat 994 loader, a Cat 5120 hydraulic excavator, four Cat 992 loaders and other support equipment. Thirteen 240t Cat haul trucks, three 170t Cat 793 haul trucks and 11 100t Cat 777D haul trucks carry waste and ore from the pits.
Diamond recovery at Ekati mine
In the process plant, a gyratory primary crusher reduces ore to minus 300mm, coarse ore being stockpiled in a 20,000t-capacity storage building. A hot water-flushed cone crusher reduces the ore to 75mm before a high pressure roll crusher reduces it to minus 25mm.
Primary and secondary scrubbers and degritting and sanding sections remove fine waste material for disposal. Heavy-medium separation (HMS) using slurried water and ground ferrosilicon separates a diamond concentrate from the crushed ore. Finally, X-ray fluorescence sorters are used to extract the diamonds from the HMS concentrate.
The development of the $182m Panda underground project was completed in 2006. It produces approximately 2,600t/d of ore and provides approximately 40% of Ekati's output by value.
The Koala underground mine was approved in June 2006 and production started in December 2007. The mine produced about 6.8Mct of diamonds grading at 1.50 carats a tonne until the first half of 2013. An additional 5.8Mt is anticipated to be mined from underground mining by 2019.
In June 2011, BHP Billiton planned a $400m expansion of the Misery open-pit project. The mining operations are expected to start in late 2015 and have a mine-life of two years.
Production, sales and marketing
The mining processes consist of excavation, cleaning and diamond separation. The mine employs about 800 full-time staff and 700 contractors.
The mine produced about 45Mct of diamonds out of six open pits between 1998 and 2009. The Ekati mine diamonds are sold under Aurias brand name and genuineness is verified through CanadaMark service.
For the year ended 31 January 2014, the company sold approximately 1.3 million carats from Ekati mine for a total of $399.6m. The mine expects to process approximately 2.6Mt of mineral reserves and produce approximately 0.9 million carats in the fiscal year 2015. The Fox pipe is expected to provide approximately 1.7 million tonnes of feed, while the Koala underground operations are estimated to provide approximately 0.9 million tonnes.
The rough diamonds are sorted in Antwerp, Toronto and Mumbai and the resulting sales parcels are distributed to Belgian and Indian subsidiaries for sale. All the mine production is sorted and valued at Yellowknife prior to shipment for sale.
The Ekati mine is accessed via a 500km seasonal ice road, which will be rebuilt every year. The only other transportation mode is by air from Yellowknife.
A consortium known as Ekati Construction Alliance was the general construction contractor for the Ekati mine. The consortium included JT, Ryfran Electric, Clark Builders, Adco North, Nahanni, GAP Electric, Hay River Mechanical, and JSL.
Finning and Transwest Mining Systems provided heavy duty mechanics and apprentice services. Nuna Logistics provided equipment operators and labourers for the project.
The contract for the construction of camp infrastructure at the push back expansion project of the Misery Pit was awarded to the joint venture of Det'on Cho Nahanni Construction.
Procon Holding was contracted to conduct underground development for the Ekati mine..
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