Source:
p. 48
GRI has applied to Mineral License and Safety Authority (MLSA) for the transfer of ownership of License No.2018/11 to a wholly owned Greenland-based subsidiary, GRI A/S. The purpose for the transfer is to fulfill a legal requirement for conversion of the MEL to an Exploitation Licence. At the time of writing, the transfer request was awaiting approval from MLSA.
Deposit Type
- Porphyry
- Hydrothermal
- Intrusion related
- Breccia pipe / Stockwork
Summary:
Malmbjerg is a porphyry molybdenum Project similar in style and morphology to the Climax Project, in Colorado, USA. Projects of this type are typically large, measuring in the hundreds of millions of tonnes with molybdenite (MoS2) contents typically measuring less than 1% of the rock by weight. Late hydrothermal processes related to the intrusions were responsible for alteration and deposition of molybdenum sulphide mineralization.
The mineralization occurs as a diffuse zone of molybdenite (± accessory tungsten) in fractures and stockworks in both the intrusives and sandstones. Molybdenite occurs as fracture-fillings and disseminations in association with hydrothermal alteration. The Project is broadly dome shaped with an outside diameter of up to 600 m and a height of approximately 150 m.
Host rocks for the Malmbjerg Project comprise Mid-Tertiary alkalic leuco-granite stocks and clastic sedimentary rocks of the Lower Permian Rode Group. The sedimentary rocks are primarily arkosic and conglomeratic sandstones that have been variously hornfelsed. Intrusive rocks consist of four principal phases: perthite granite, quartz porphyry (Arcturus porphyry), porphyritic aplite, and weakly feldspathic quartz porphyry (Schuchert porphyry). In the western cliff face of Høstakken Mountain, the intrusive/sediment contact is plainly visible, forming a broad arch with the Rode Group rocks draped over top.
Contact relationships within the intrusion are complex and are often ambiguous. The perthite granite is the most widespread phase and is believed to be the oldest. The perthite shows gradational contacts with the Arcturus porphyry, which is compositionally similar to the perthite and is discriminated primarily on the basis of texture. The Arcturus porphyry tends to occur at the top and on the northeast side of the intrusion. Its chemical similarity and complexly interlayered relationship to the perthite granite suggest that the Arcturus may just be another phase of the perthite granite. Following the Arcturus porphyry was the aplite, which occurs as both porphyritic and non-porphyritic variants. The final phase is the Schuchert porphyry, which occupies the northern portion of the Project. The Schuchert is observed to crosscut the perthite granite and the aplite. Silicification, noted in the perthite and aplite, is not seen in the Schuchert porphyry, indicating that it post-dates this alteration event.
Post-mineralization basic and trachytic dikes have been mapped and occur within the Project. The basic dikes are quite narrow, usually decimetre-scale, are steeply-dipping and trend in a NE-SW direction. The trachytes occur as two 5 m to 15 m thick subvertical sheets, striking east-northeasterly. Lamprophyre dikes have been noted in the area but have not been identified in the drift mapping or drillhole logs. K-Ar dates for the intrusives place the age of emplacement at around 25 Ma, which is late Oligocene.
Molybdenite occurs as fracture-fillings and disseminations in association with hydrothermal alteration. The Project is broadly dome shaped with an outside diameter of up to 600 m and a height of approximately 150 m. Accessory pyrite occurs as a halo around the molybdenite zone. Other accessory minerals include minor amounts of wolframite, scheelite, and fluorite. Re-assays done in 2021 confirmed ICP results having below DL (<10 ppm) uranium. There is also very minor galena, sphalerite, and chalcopyrite occur in veinlets at the periphery of the Project.
MoS2 grades tend to level off at approximately 0.35% in the central high-grade core, although local grades of over 1% have been observed. The grades gradually taper off to ppm range with distance outwards and downwards. The mineralization continues up into the sedimentary rocks in the roof of the Project, but the grades are observed to diminish more rapidly than in the intrusives.
Alteration at Malmbjerg occurs as concentric zones of assemblages typical of many porphyry deposits. The innermost zone consists of a silicified zone, which is surrounded by a halo of sericite-K-feldspar alteration, and finally a biotite-magnetite-quartz zone. Extending for up to 500 m from the Project is a large zone of pyrite mineralization that has resulted in a large gossan over the surface exposures surrounding the Project.
Summary:
The Malmbjerg Molybdenum Project comprises of a conventional open pit mine producing 35,000 t/d of Mo rich ore for processing in a conventional base metal sulphide concentrator. The mine plan equipment fleet consists of two x 34 m3 hydraulic shovels loading 13 x 230 t haul trucks operating on 12 m benches. The operational mining plan will utilize an economic grade control system where higher value ore will be separated and transported to the concentrator while the lower value ore will be stockpiled and processed at the end of conventional mining. Waste rock will be stored on the west side of the deposit and used for haul road and construction activities at the mine site. Current mining reserves dictate a mine life of 20 years where the concentrator will be fed directly from the open pit for a period of 11 years, and stockpiled ore will be processed for the remaining 9 years.
Two-way in-pit haul roads of 32 m widths are designed to support the use of 230-t payload haul trucks. Haul road grades are limited to a maximum of 8%. Access ramps are not designed for the last bench above the pit bottom elevation, assuming that the ramp segment accessing the pit bottom will be removed using retreat mining. The bottom two ramped benches of the pit use one-way haul roads of
23 m width and 12% grade since bench volumes and traffic flow are reduced.
Ultimate pit limits are split into phases or pushbacks to target higher economic material earlier in the mine life with lower strip ratios. A minimum pushback width of 75 m is used between each phase.
The final detailed pit designs include three pit phases.
Phase 1 – This phase contains approximately four years of mill feed. The phase mines from 1,098 m to the phase bottom at 594 m. The ramp runs down the highwall of the pit providing access to multiple external ramps and access for phase 2 mining. The bottom of the pit is accessed by a ramp that exits onto an external haul road at the 678 m and 726 m elevation.
Phase 2 – This phase pushes out the northeastern portion of the previous phases with enough room for another pushback. The phase contains approximately six years of mill feed. The phase mines from the crest at 1,194 m to the phase pit bottom at 606 m. The main ramp runs down the highwall of the pit connecting to the same external ramps as phase 1 and allowing access for phase 3 mining. The bottom of the pit is accessed from a ramp that exits onto an external haul road at the 678 m and 738 m elevation.
Phase 3 – This phase pushes out the pit to the ultimate limits in the north, northeast, and northwest. The phase contains approximately 10 years of mill feed and mines from the pit crest at 1,098 m elevation down to the pit bottom of 522 m elevation. The phase is accessed by ramps left in phase 2 highwalls connecting to external ramps located on the mountainside. The bottom of the phase is accessed from a ramp that exits onto an external haul road at 720 m elevation. Geotechnical berms are left behind on the 786 m, 930 m, and 1,074 m benches. Future design iterations should implement wider benches and shallower overall slope in the southeast wall as per KP recommendations from a review of the 2022 pit designs. Pit slope sensitivity analysis show that the ultimate pit limit is not sensitive to slope angle changes in this area, therefore these changes will not materially impact the ore tonnages.
Mine Operations
Mine operations are planned to be typical open pit operations in steep, mountainous, and snow-covered terrain.
Grade control – blast hole sampling: an ore control system is planned to provide field control for the loading equipment to selectively mine ore-grade material separately from the waste.
In-situ rock will be drilled and blasted on 12 m benches to create suitable fragmentation for efficient loading and hauling of material. Various drill and blast patterns and powder factors are planned for wet and dry conditions and highwall/trim blasting to prevent overbreak and maintain the stability of the high walls.
Blasting activities are planned to be entirely under a contract service agreement with the explosive supplier. Dry conditions are proposed to be done using a bulk Ammonium Nitrate Fuel Oil (ANFO) product and wet conditions with a blended emulsion product. On average, an estimated 20% of blast holes are expected to be wet. The explosive plant will be located southwest of the pit. Powder factor targets are 0.28 kg/t for the production blasting of wet and dry holes.
Loading of ore and waste will be completed with hydraulic mining shovels and front-end wheel loaders on 12 m benches.
Rock will be hauled out of the pit to scheduled destinations with off-highway rigid frame haul trucks.
Mine pit services will include the following:
- haul road, pit access roads and ramps and pit floors maintenance;
- stockpile management;
- in pit dewatering;
- equipment, fuel, and lube services;
- temporary lighting;
- personnel and consumables transportation;
- mine rescue and safety;
- gravel and glacier road maintenance.
Direct mining operations and mine fleet maintenance are planned as an Owner’s fleet. Mining operations are based on 365 operating days with two 12-hour shifts per day. An allowance of 10 shutdown days is built into the mine schedule to allow for adverse weather conditions or equipment mechanical availability issues.
The total number of hourly mine operations personnel, including hourly maintenance personnel, peaks at 167 persons. Due to shift rotation, only one-quarter of personnel will be on shift at a given time. Salaried personnel peaks at 48 persons and will be required f or mine operations, including mine and maintenance supervision, mine engineering, and geology.
Flow Sheet:
Crusher / Mill Type | Model | Size | Power | Quantity |
Gyratory crusher
|
|
1372 x 1905mm
|
600 kW
|
1
|
Jaw crusher
|
|
|
|
1
|
Cone crusher
|
|
|
370 kW
|
2
|
SAG mill
|
|
10.36m x 5.21m
|
8 MW
|
2
|
Ball mill
|
|
6.1m x 9.1m
|
4.2 MW
|
2
|
Vertical mill / Tower
|
|
|
500 kW
|
1
|
Vertical mill / Tower
|
|
|
150 kW
|
1
|
Summary:
ROM ore will be transported from the open pit mine to the primary gyratory crusher by 240 t haul trucks. The ore will be screened through a static grizzly screen with a 1,000 mm aperture, and the grizzly oversize will be broken using a hydraulic rock breaker.
The gyratory crusher will crush the grizzly screen undersize to a particle size of 80% passing 125 mm at an average throughput of 2,244 t/h and dropped on an apron feeder. The apron feeder discharge will be conveyed using a sacrificial belt conveyor to the RopeCon conveyor feed chute. The RopeCon conveyor will convey the crushed ore from the mine site to the port site. At the port site, the RopeCon conveyor discharges the crushed ore onto the live crushed ore stockpile.
The main equipment installed at the crushing facilities will be:
- One 1.372 m x 1.905 m gyratory crusher with 600 kW installed power;
- A hydraulic rock breaker;
- One 2.1 m wide x 8.0 m long apron feeder;
- One 1.35 m wide x 38.0 m long sacrificial belt conveyor.
The RopeCon conveyor will consist of four sections to navigate around the rough terrain o f the Malmbjerg Project site. The total length of the system will be approximately 21.7 km. The RopeCon conveyor will discharge the crushed ore onto the live crushed ore stockpile.
Dust collectors will be installed at the crushing facility to control fugitive dust generated during crushing and conveying. The sacrificial belt conveyor will be equipped with a belt scale, metal detector and a magnet/metal separator to protect the RopeCon conveyor against damages caused by metal pieces.
The total live capacity of the crushed ore stockpile is approximately 35,000 t. The crushed ore stockpile will be covered. The ore will be reclaimed from the live stockpile in two parallel lines, each feeding a grinding line in the grinding process barge. Two parallel lines allows the process plant to run at 50% capacity when one grinding train is down.
Each line will be equipped with three 1.2 m wide x 7.2 m long reclaim apron feeders (two operating and one standby) operating at a nominal rate of 396 t/h per feeder. The stockpile reclaim area will also be equipped with a dust collection system to minimize the spread of dust generated during ore handling and transportation to the mill. The stockpile reclaim tunnel area will be equipped with sumps and pumps to recycle any spillage.
The reclaimed ore from the apron feeders will be discharged on two parallel 1.05 m wide x 119.1 m long belt conveyors. Each conveyor will be equipped with a weightometer to measure the fresh feed flow rate to the SAG mill.
The crushed ore from the stockpile will be fed into two SAG mills on the grinding process barge by two separate SAG mill feed conveyors. Two separate automatic ball charging systems will be provided to add grinding media to the SAG mills at a controlled rate. The SAG mills will be equipped with 76 mm discharge pebble ports to remove undersize materials, including critical size pebbles. The mill discharge from each SAG mill will be screened by a SAG mill trommel and then a double deck vibrating screen with a 25 mm aperture size for the top deck and a 12.5 mm aperture size for the bottom deck. The trommel and screen undersize will flow by gravity to a pump box and be pumped to the secondary grinding circuits via the cyclones. The SAG mill area will be equipped with sloped floors, sumps, and pumps to drain, collect and recycle any spillage.
The oversized material from the vibrating screens will be conveyed to a common pebble crusher feed surge bin. Each surge bin feed conveyor will be equipped with two cleaning magnets and one metal detector to remove/detect any tramp metal to protect the pebble crushers. The pebble crusher feed surge bin will have a live capacity of 400 t. The pebbles will be reclaimed by two 1.5 m wide x 11.5 m long belt feeders, which will feed the pebble cone crushers. The crusher will crush the pebbles to a particle size of 80% passing 12.5 mm. The crushed pebbles will be directed to the SAG mill feed conveyors.
The major equipment of the primary grinding and classification circuit are:
- Two 10.36 m diameter x 5.21 m EGL SAG mills, each with 8 MW installed power;
- Two 3.6 m wide x 7.3 m long double deck vibrating screens;
- Two pebble (cone) crushers, each with 370 kW installed power.
The secondary grinding circuit will include two balls mills, each in reverse closed circuit with one cyclone cluster. The secondary grinding circuit will grind the SAG mill product to a particle size of 80% passing 180 µm.
The major equipment items in the secondary grinding circuits are:
- Two 6.1 m diameter x 9.1 EGL ball mills, each with 4.2 MW installed power;
- Two cyclone clusters, each consisting of six 710 mm diameter cyclones (five operating and one standby);
- Particle size analyzer.
The SAG mill screen undersize from each primary grinding circuit will be gravity fed to the cyclone feed pump box. The SAG mill circuit product and the ball mill discharge will be pumped to the respective cyclone cluster. The cyclone underflow will flow by gravity to the ball mills, while the cyclone overflow will be sent to the downstream flotation circuit at a pulp density of approximately 42.5% (w/w).
A particle size analyzer will be installed to monitor the particle size of the cyclone overflow and to facilitate the production of ground slurry at the required particle size. Two separate automatic ball charging systems will be provided to add grinding media to the ball mills at a controlled rate. The ball mill area will be equipped with sumps and pumps to recycle any spillage.
Processing
- Filter press plant
- Dewatering
- Flotation
Flow Sheet:
Summary:
The processing plant is designed to process mill feed at a nominal throughput of 35,000 t/d for an average annual throughput of 12.8 Mt. The processing of the porphyry molybdenum ore will include crushing, grinding, flotation, and dewatering as the main operations producing a marketable Mo concentrate.
Rougher Flotation and Regrinding
The cyclone overflow will be fed to a 300 m3 conditioning tank. Kerosene collector reagent and W31 frother will be added to the conditioning tank at the required dosage rates. Process water will be added to the tank to reduce the slurry pulp density to 38% (w/w). The conditioned slurry will be fed to the rougher flotation bank.
The rougher flotation bank will consist of four 300 m3 tank cells for rougher flotation and three 300 m3 tank cells for rougher scavenger flotation. The concentrate from the rougher and the rougher scavenger flotation cells will be gravity fed to the rougher concentrate regrind cyclone feed pump box. The ........

Recoveries & Grades:
Commodity | Parameter | Avg. LOM |
Molybdenum
|
Head Grade, %
| 0.106 |
Molybdenum
|
Concentrate Grade, %
| 54 |
Reserves at February 8, 2022:
Mineral Reserves are reported at a cut-off NSR of $11.14/t NSR (diluted). The cut-off value covers the processing + G&A costs of $8.34/t, ore transport costs of $0.14/t, and stockpile rehandle costs of $1.25/t.
Mineral Resource base case cut-off grade within the “reasonable prospects of eventual economic extraction” constraining pit is an MoS2 grade of 0.08% which corresponds to a Net Smelter Return (NSR) of $14.79/t.
Conversion from MoS2 to Mo is 0.599 based on the respective atomic weights.
Category | Tonnage | Commodity | Grade | Contained Metal |
Proven
|
123 Mt
|
Molybdenum
|
0.121 %
|
328 M lbs
|
Probable
|
122 Mt
|
Molybdenum
|
0.09 %
|
243 M lbs
|
Proven & Probable
|
245 Mt
|
Molybdenum
|
0.1 %
|
571 M lbs
|
Measured
|
128 Mt
|
Molybdenum
|
0.12 %
|
345 M lbs
|
Indicated
|
153 Mt
|
Molybdenum
|
0.1 %
|
317 M lbs
|
Measured & Indicated
|
281 Mt
|
Molybdenum
|
0.11 %
|
661 M lbs
|
Inferred
|
33 Mt
|
Molybdenum
|
0.06 %
|
42 M lbs
|
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