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Gahcho Kué

The Gahcho Kué diamond mine is a joint venture between Mountain Province Diamonds, which owns 49% of the project, and De Beers Canada, which holds a 51% interest and is the mine’s operator.

91.40 Carat Rough Diamond

Location

The property is located in the Northwest Territories of Canada, 300 km east-northeast of Yellowknife. The site lies on the edge of the continuous permafrost zone in an area known as the barren lands.

The surface is characterised as heath/tundra, with occasional knolls, bedrock outcrops, and localised surface depressions interspersed with lakes.

A thin, discontinuous cover of organic and mineral soil overlies bedrock, which typically occurs within a few metres of surface.

Small stands of stunted spruce dot the area. Numerous lakes cover the landscape. Kennady Lake, under which the kimberlite pipes lie, is a local headwater lake with a minimal catchment area.

Introduction to Gahcho Kué

Mine Plan

At Gahcho Kué, Mountain Province Diamonds is mining three kimberlite pipes in a sequence that maximizes the value of the contained ore. Mining began with 5034 pipe, followed by Hearne, and will later incorporate ore from Tuzo, with production from all three pits overlapping at times. The recently discovered Wilson pipe lies well within the open pit mine plan for Tuzo.

5034 PIPE

  • First kimberlite pipe discovered in the project area
  • Lies under and adjacent to Kennady Lake
  • Subdivided on the basis of internal geology into four lobes
  • Abundant with Hypabyssal Kimberlite
  • Initial pipe to be mined

NI 43-101(1)
Grade (cpt) - 1.91
Production (Mct) - 18.4
Life of mine - Current life of mine extends to 2028

HEARNE PIPE

  • Subdivided into a northern and a southern lobe
  • Hearne North is a narrow elongate pipe abundant with Hypabyssal Kimberlite and Tuffisitic Kimberlite Breccia
  • Hearne South is a roughly circular pipe abundant with Tuffisitic Kimberlite Breccia
  • Mining commenced in Q2 2018

NI 43-101(1)
Grade (cpt) - 1.99
Production (Mct) - 10.9
Life of mine - Current life of mine extends to 2028

TUZO PIPE

  • Ellipsoidal pipe subdivided into three zones that continue to a depth of 300m
  • Abundant with Tuffisitic Kimberlite Breccia
  • Mining expected to begin in xxx
  • Potential to further develop Tuzo Deep to extend the mine life

NI 43-101(1)
Grade (cpt) - 1.22
Production (Mct) - 19.1
Life of mine - Current life of mine extends to 2028

The newly discovered WILSON kimberlite

  • First new kimberlite discovery at Gahcho Kué in 20 years
  • Lies near surface under recent lake sediment
  • Intersects up to 119 m of Tuffisitic Kimberlite and Hypabyssal Kimberlite
  • Microdiamond results include a 0.28 carat diamond recovered from a 115.2 kg sample
  • Well within the open pit mine plan for Tuzo pipe
  • Named after Alice Evelyn Wilson (1881-1964), who is officially recognized as Canada's first female geologist.

Geology

The Kennady Lake kimberlite cluster is in the southeast Slave Craton. The kimberlite pipes were emplaced in the Cambrian Period around 540 Ma into Archean host granodiorite, high-grade gneiss, migmatite, and volcanic and supracrustal rocks that range in age from 4.05 to 2.55 Ga. Erosional processes have since stripped the kimberlites almost to their root zones, preserving only some of the hypabyssal and diatreme facies.

The area was glaciated repeatedly during the Pleistocene, most recently by the Laurentide ice sheet. The Laurentide ice sheet began to recede about 18,000 years ago, retreating past the Kennady Lake project area between 9,000 and 9,500 years ago.

Four main pipes comprise the Kennady Lake kimberlite cluster - 5034, Hearne, Tuzo and Tesla. The 5034 kimberlite is an irregular hypabyssal root zone. Hearne and Tesla are transitional diatremes and root zones. Tuzo is the deeper part of a diatreme zone. At present, Tesla is not included in the Gahcho Kué mineable resource because of its relatively small size (0.4 ha). However, it may be exploited towards the end of the project life. The recently discovered Wilson kimberlite is still being explored.

The shapes and internal geology of each of the kimberlite pipes have been interpreted based on geological logging of drill core. The external shapes and internal geology of each body have been modeled in three dimensions using GEMCOM modelling software. Both internal and external models were updated after drilling programs conducted between 2001 and 2011. All the pipes remain open to depth.

Plan view of the Wilson kimberlite. Inset shows the location relative to other kimberlites at Gahcho Kué. The planned open pit mine pit shells are shown in pale gray.

Preliminary cross-section of the Wilson kimberlite in green, looking east from Tuzo. Drill traces are shown as black lines. Lake surface and bottom sediments are outlined in brown. The proposed open pit profile for the Tuzo kimberlite is in gray. Elevations are in meters above sea level. Not all drill traces are shown. Drilling to date shows no connection to the nearby Tuzo kimberlite, and the Wilson kimberlite remains open to the north.

91.40 Carat Rough Diamond

Site History

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