Overview
Stage | Permitting |
Mine Type | Underground |
Commodities |
|
Mining Method |
- Transverse stoping
- Longitudinal retreat
- Paste backfill
|
Processing |
- Sulfuric acid (reagent)
- Solvent Extraction
- Calcining
- Counter current decantation (CCD)
- Acid tank leaching
|
Mine Life | 9 years (as of Jan 1, 2018) |
Latest News | NexGen Announces C$150 Million Bought Deal Financing February 25, 2021 |
Source:
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The Project is wholly-owned by NexGen. The Rook I Project consists of 32 contiguous mineral claims with a total area of 35,065 ha. As of November 29, 2018, all 32 mineral claims were in good standing and registered in the name of NexGen Energy Ltd.
Deposit Type
- Vein / narrow vein
- Unconformity related
Summary:
The Arrow Deposit and other exploration targets at the Property belong to the unconformity-associated class of uranium deposits. This type of mineralization is spatially associated with unconformities that separate Paleo- to Mesoproterozoic conglomeratic sandstone basins and metamorphosed basement rocks (Jefferson et al., 2007).
The mineralization is known to occur at seven locations on the Rook I Property: 1) Arrow Deposit, 2) Harpoon occurrence, 3) Bow occurrence, 4) Cannon occurrence, 5) Camp East occurrence, 6) Area A occurrence, and 7) South Arrow occurrence, the most significant of which is the Arrow Deposit. All uranium mineralization discovered on the Property to date is hosted exclusively in basement lithologies below the unconformity.
ARROW DEPOSIT
Uranium was first discovered at Arrow by NexGen in February of 2014 when drill hole AR-14-01 intersected modest mineralization including 0.16% U3O8 over 9.0 m. Subsequent follow-up drilling identified a zone of extensive mineralization highlighted by drill holes AR-16-63c2, which intersected 15.20% U3O8 over 42.0 m and an additional 12.99% U3O8 over 46.5 m, AR-15-62, which intersected 6.35% U3O8 over 124.0 m, and AR-15-44b, which intersected 11.55% U3O8 over 56.5 m including 20.0 m at 20.68% U3O8 and 1.0 m at 70.0% U3O8. These drill holes intersected the mineralization at a low angle and therefore the core lengths do not represent the width of the mineralization.
Uranium mineralization at the Arrow Deposit dominantly occurs as uraninite. Other common uranium minerals include coffinite and secondary yellow coloured minerals, currently interpreted to be autunite, carnotite, and/or uranophane. A green coloured secondary uranium mineral interpreted to be torbernite has also been observed very locally. In zones of massive uraninite mineralization, blebs of a glassy black coloured phase with conchoidal fracture currently interpreted to be pyrobitumen are often observed.
Two key but contrasting types of uranium mineralization occur at Arrow:
• Open-space fillings
Open-space fillings include massive uraninite bodies interpreted to be uranium veins, and breccia bodies where the matrix is comprised nearly exclusively of massive uraninite. Uranium veins and breccias typically range in thickness from less than 0.1 m to greater than one metre and display sharp contacts with the surrounding wall rocks. Individual uranium veins usually occur at parallel to sub-parallel orientations to the regional foliation, however, at least one set of veins cross-cuts the regional foliation. Clasts present in uranium breccias at Arrow are typically fragments of the immediate wall rocks and often contain additional disseminated uraninite mineralization. Uranium breccias occur as both clast supported and matrix supported forms, with the latter typically hosting higher grades. Both styles of open-space filling mineralization are categorized by high uranium grades that can be in excess of 40% U3O8 and as high as 80% U3O8.
• Chemical replacement styles
Chemical replacement types of mineralization present at Arrow include disseminated, worm-rock and near complete to complete replacement styles. Disseminated mineralization is typically associated with strong to intense hydrothermal alteration where uraninite occurs as fine to medium grained anhedral crystals and crystal agglomerates spread throughout the host in concentrations of typically less than five modal percent. Worm-rock style mineralization is named for the wormy texture it by definition displays, which is the result of redox reactions between uranium bearing fluids and the host wall rocks. Typically, these redox fronts are less than 10 cm thick. Near to complete uraninite replacement of the host rock has also been observed at Arrow. These zones range in thickness from less than 0.1 m to greater than 1.0 m and, in contrast to open- space fillings, show gradual contacts. The presence of vugs in this style of mineralization and in some zones interpreted to be uraninite veins suggests that in at least some places, the veins may actually be the result of chemical replacement and not open-space filling. Uranium grades associated with chemical replacement styles of mineralization at Arrow range from less than 1% U3O8 in disseminated bodies to greater than 70% U3O8 in complete replacement bodies.
Hydrothermal alteration that occurs in the vicinity of Arrow is extensive and several distinct styles have been observed. In some areas, mineralization is closely associated with a pervasive quartz-sericite-sudoite-illite alteration assemblage that nearly completely replaces the host rock, although pre-alteration textures are often preserved. In other areas, mineralization is closely associated with pervasive brick red coloured hematite alteration. Another key alteration phase present at Arrow is dravite. Typically, it occurs in centimetre to decimetre wide breccia vein bodies beginning tens of metres from high grade uranium mineralization and increasing in size and frequency closer to mineralization. Carbon buttons are commonly observed in association with dravite. Centimetre sized drusy quartz veins occur ubiquitously in the vicinity of the deposit. Where proximal to high grade mineralization, these veins are often pink coloured.
The mineralization in the Arrow Deposit is sub-vertical and true width is estimated to be from 30% to 50% of reported core lengths based on currently available information.
Mining Methods
- Transverse stoping
- Longitudinal retreat
- Paste backfill
Summary:
Two longhole mining methods will be used to extract the ore:
- Transverse stope mining
- Longitudinal retreat stope mining.
Both longhole mining methods will use paste backfill to provide ground stability. This combination of longhole stoping using paste backfill will provide a combination of good productivity, high extraction, and stable back support.
All stope designs were completed using the Deswik Stope Optimizer (DSO) tool. The longhole stope design parameters were based on 30 m stope heights for both transverse and longitudinal stopes. For transverse stopes, the width of the primary and secondary stopes was set at 15 m, while a maximum strike length was not specified. For longitudinal stopes, the width of the stopes was set at a minimum of 3.0 m (including 1.0 m of dilution), and no maximum width, and a strike length of 15 m. After an initial result from DSO, a secondary evaluation of stopes with heights of 10 m and 20 m was completed to capture material that was not converted into mine shapes during the first pass.
Transverse longhole mining will be done using primary and secondary stoping methods. The order in which stopes are extracted is largely driven by the head grade, with the overarching goal of achieving annual production of 30.0 M lbs U3O8. Two separate vertical mining blocks (the Upper Block, and Lower Block) will be established, and within each vertical block, the A2 and A3 veins can be mined independently.
The Arrow deposit is planned to be accessed using two shafts. Both shafts will be located in the footwall of the deposit. They will both have an internal diameter of 6.5 m, and will be blind- bored concurrently, using conventional shaft sinking technologies.
The first shaft will be used as a production shaft, and for transportation of personnel and materials into the mine. Shaft #1 will be sunk to a depth of 658 m below surface. Shaft #1 will have divided compartments so that fresh air that comes into contact with ore being skipped to surface will be immediately exhausted within the mine. Shaft #1 will have a permanent headframe and hoisting house.
The second shaft will be used as an exhaust ventilation shaft. Shaft #2 will be sunk to a depth of 533 m below surface. An emergency escapeway system will also be installed in Shaft #2.
Processing
- Sulfuric acid (reagent)
- Solvent Extraction
- Calcining
- Counter current decantation (CCD)
- Acid tank leaching
Flow Sheet:
Summary:
Ore Sorting and Storage
Ore will be crushed underground and will be suitably sized to feed the grinding mill. The hoisted ore will be loaded into an ore truck at the headframe. The truck will drive through a radiometric scanner to confirm ore grade and the delivery location of the ore on the ore pad. Different ore grades and types can be stored in different piles.
Grinding
A loader operator will deliver ore to the ore feed hopper. Traffic in the ore storage and reclaim area will be restricted to minimize ore contamination in the site area. A variable speed feeder belt will feed ore from the hopper into the semi-autogenous grind (SAG) mill at a prescribed rate that will be close to the ground ore feed rate to be fed to mill leaching. The ore will be weighed on the belt as well as given a gamma radiation scan to check uranium content.
Leaching
The first leach tank will be fed by a variable speed centrifugal pump to feed the prescribed solids rate t ........

Recoveries & Grades:
Commodity | Parameter | Avg. LOM |
Uranium (U3O8)
|
Recovery Rate, %
| ......  |
Uranium (U3O8)
|
Head Grade, %
| 3.09 |
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Projected Production:
Commodity | Units | Avg. Annual | LOM |
Uranium (U3O8)
|
M lbs
| 25 | 228 |
All production numbers are expressed as U3O8.
Operational Metrics:
Metrics | |
Daily ore mining rate
| ......  |
Ore tonnes mined, LOM
| ......  |
Annual production capacity
| ......  |
Daily processing capacity
| ......  |
Tonnes processed, LOM
| ......  |
Annual processing capacity
| ......  |
* According to 2018 study.
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Reserves at November 5, 2018:
Category | Tonnage | Commodity | Grade | Contained Commodity |
Probable
|
3,433,100 t
|
Uranium (U3O8)
|
3.09 %
|
234,100,000 lbs
|
Indicated
|
2,890,000 t
|
Uranium (U3O8)
|
4.03 %
|
256,600,000 lbs
|
Inferred
|
4,840,000 t
|
Uranium (U3O8)
|
0.86 %
|
91,700,000 lbs
|
Corporate Filings & Presentations:
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News:
News | Date |
NexGen Announces C$150 Million Bought Deal Financing
|
February 25, 2021
|
NexGen Announces Elite Environmental and Economic Results from the Rook I Feasibility Study
|
February 22, 2021
|
NexGen Closes US$30 Million Financing with Queen's Road Capital
|
May 28, 2020
|
NexGen Announces US$30 Million Financing with Queen's Road Capital
|
May 11, 2020
|
NexGen Demonstrating Continuity of Grade and Thickness at Arrow
|
December 12, 2019
|
NexGen Signs Four Study Agreements With Local Communities
|
December 5, 2019
|
NexGen Releases Second Batch of Assay Results from the 2019 Feasibility Stage Drilling Program, Intersects High-Grade Uranium in All A2 and A3 High-Grade Domain Targets
|
November 20, 2019
|
NexGen Releases First Assays from Recently Completed Arrow Drilling Program Including 12.0 m at 33.78% U3O8 and 8.0 m at 32.88% U3O8
|
October 9, 2019
|
NexGen Continues to Intersect High-Grade Mineralization in all A2 and A3 Targets Highlighting Strength of Continuity at Arrow
|
July 10, 2019
|
NexGen Announces the Commencement of an Environmental Assessment for the Rook I Project
|
April 29, 2019
|
NexGen Releases Results from Shaft Pilot Hole Report and Assays from the Development Drilling Summer 2018 Program
|
February 14, 2019
|
NexGen Energy Announces Filing of Pre-Feasibility Study Report on the Arrow Deposit, Rook I Project
|
December 20, 2018
|
NexGen Energy Announces Pre-Feasibility Study Results, Arrow Deposit
|
November 5, 2018
|
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