Overview
Stage | Feasibility |
Mine Type | Open Pit |
Commodities |
|
Mining Method |
|
Processing |
- Gravity separation
- Dewatering
- Filter press plant
- Intensive Cyanidation Reactor (ICR)
- Carbon re-activation kiln
- Centrifugal concentrator
- Concentrate leach
- Agitated tank (VAT) leaching
- Carbon in pulp (CIP)
- Elution
- Carbon adsorption-desorption-recovery (ADR)
- Solvent Extraction & Electrowinning
- Cyanide (reagent)
|
Mine Life | 10.9 years (as of Jan 1, 2021) |
Goldboro Open Pit mine is Phase 1 of long term development plan, which in the future will consider further technical studies to incorporate the high-grade underground mineral resource into the operation. |
Latest News | Anaconda Mining Files The Positive Phase I Open Pit Feasibility Study For The Goldboro Gold Project January 20, 2022 |
Source:
p. 29
The Goldboro Property consists of 37 contiguous claims, registered through Anaconda’s wholly-owned subsidiary Orex Exploration Inc.
Deposit Type
- Orogenic
- Metamorphic
- Vein / narrow vein
Summary:
The Deposit is a turbidite-hosted orogenic gold deposit hosted within a sequence of alternating argillites and greywacke metamorphosed to greenschist facies. These deposit types are typically characterized by the formation of gold bearing quartz veins within the argillite units, commonly referred to as mineralized Belts, that are interbedded with greywacke units. There are currently 68 stacked mineralized Belts ranging in thickness from 1 m to 20 m in the Deposit. The metasedimentary units on the Property are folded into the tight, gently east-plunging Upper Seal Harbour Anticline and gold mineralization has typically been deposited at various positions and times during the fold formation process. Veins, which form during deformation, occur in three major geometries commonly referred to as reefs: saddle reefs, leg reefs, and spur reefs. Saddle reefs occur about the apex of the fold and are the dominant vein types within some deposits. Leg reefs extend down the limbs of the fold, beyond the saddle reef, and are generally parallel with the metasedimentary layers. These are also commonly termed BP veins in the Nova Scotia goldfields. Spur reefs are veins that cross between layers and may be in the apex of the fold or on its limbs. This style of vein is in part captured under the term “angular” in the Nova Scotia goldfields.
The Deposit contains all three types of reefs outlined above but is also characterized by mineralization within the argillite forming the Belts. Because the Deposit contains saddle, leg, and spur reefs, and often has gold mineralization within the argillite hosting the veins, it has the potential to contain significantly more gold resources than deposits of a similar style that contain gold only within the quartz veins (reefs) themselves. The trace of the Upper Seal Harbour Anticline transects the Property and is found near the Dolliver Mountain prospect 2 km to the west of the Deposit, demonstrating that the structure which hosts gold continues for several kilometres.
The Project is underlain by rocks within the Goldenville Formation dominated by greywacke and argillite. At the Deposit, the Goldenville Formation consists of alternating greywacke and argillite beds with an approximate true thickness of 950 m. The base of the stratigraphic sequence intersected in the BR Gold System consists of roughly 325 m of alternating greywacke and argillite, with varying proportions of both rock types, ranging in thickness from less than 1 m up to 10 m. This is overlain by the Marker Horizon, which consists of a 40 m to 50 m greywacke bed that is commonly intersected during drilling and in underground workings.
High-grade gold mineralization at the Deposit occurs in both quartz veins and host argillite . These high-grade zones are BP and generally continuous around the fold hinge and down the north and south limbs. These mineralized zones are referred to as Belts. Sixty-eight Belts have been modelled within the Deposit and are referred to as Higher-Grade Belt within the model. A more disseminated, generally lower-grade, style of mineralization occurs in the wall rock adjacent to the quartz veins and can extend several metres outward from and between Higher-Grade Belts. These are referred to as Lower-Grade Domains and can include disseminated gold mineralization within altered, sulphide (arsenopyrite) bearing wall rock including greywacke and argillite, gold bearing quartz sulphide veins of variable orientation that do not correlate geometrically to adjacent Higher-Grade Belts.
Gold is associated with sulphide bearing quartz veins and altered, sulphidic wall rock. Arsenopyrite is the most common sulphide species present, although pyrite, pyrrhotite, chalcopyrite, galena, and sphalerite are also associated. Gold commonly occurs as a free-milling phase within quartz veins but is also present in direct association with vein hosted arsenopyrite. In such cases, it commonly occurs as inclusions within arsenopyrite, as free particles associated with microfractures cutting arsenopyrite crystals, and as free particles attached to arsenopyrite crystal surfaces (Ryan & Smith, 1998). Pyrite also coats fracture and cleavage planes closest to vein contacts and occurs as finegrained, disseminated subhedral crystals. Pyrite locally exhibits wispy and blebby textures and frequently shows association with late faults (Gervais, D.; Carrier, A.; Brousseau, K.; InnovExplo Inc., 2009).
Native gold is nuggety in nature, and grains range from microscopic up to several centimetres in size and is found in all rock types, with visible gold generally associated with quartz veins. Within quartz veins, gold is present as free gold in quartz, and within arsenopyrite grains, along grain boundaries and internal fractures, and is non-refractory in nature. Native gold also occurs as a disseminated phase in altered argillite and argillite/greywacke intervals adjacent to and separate from quartz veins, demonstrating its association with both quartz veins and the altered wall rock.
Summary:
The operation scenario studied for the FS involves:
• Open Pit mining at an average mining rate of 12.8 Mt per year.
• Gold process facility with a 1.46 Mtpa (4,000 t/d) capacity.
• Approximate 6-month ramp up period in Year 1 (YR1) for process facility.
• 1-year pre-production mining period to coincide with Tailings Management Facility Initial Stage development.
The FS is based on a conventional truck-shovel open pit mining operation within two pits. The open pit production period is approximately 10.9 years with 1 year of pre-production (prior to process plant start-up).
Waste Rock Disposal Design
Waste rock generated from the open pit will require the development of waste rock storage areas. The waste generated from the open pit includes waste rock, till, historical tailings, and topsoil and organics.
The proposed mine plan will generate approximately 126.8 million tonnes of waste material, which includes overburden. Assuming a swell factor of 30%, a volume of 61.7 million m3 of waste storage is required.
Open Pit Mining Operation
A mining contractor would be responsible, with the guidance of the Company technical staff, to provide suitable equipment and operational procedures to meet the target production. The mining equipment will depend on the available equipment of the selected mining contractor.
Drilling is expected to be performed on eight-metre benches. For ore-control may be excavated on 4 m intervals.
It is recommended that the blasting services be provided by the mining contractor, or a specialist blasting services provider. For the purposes of estimating the requirements it has been assumed that overburden material will be free digging and that the explosive product is emulsion. During operations, safe working procedures for drilling and blasting when approaching historical workings will require development.
Based on mining contractor budget quotes, a front end loader type of excavator (~7 m3 bucket capacity) and a hydraulic excavator (~8 m3 bucket capacity) were proposed for waste handling. A backhoe type excavator (~4-4.5 m3 bucket capacity) was proposed for ore handling. The haulage units proposed ranged from a single fleet of ~63t haul truck to a combination fleet of ~90t rigid frame truck with ~40t articulated haul truck.
An 8.0 m3 bucket capacity and 4.5 m3 bucket capacity were assumed when estimating the loading fleet requirements. The 90t haul truck with 40t articulated haul truck were assumed when estimating the hauling fleet.
The primary pit operations will be supported by additional equipment including track dozers with ripper attachments, road graders, water truck, utility loaders and excavators, and maintenance service vehicles, dependent on the selected mining contractor.
It is envisaged that the rock will be loaded directly into the processing plant crusher hopper but there will be a need for a ROM stockpile to allow for stoppages, for stockpiling in the pre- production period, and possibly some blending.
The progressive development of the open pit will result in increasing water infiltration from precipitation and groundwater inflows. As the pit deepens and increases in footprint, it will be necessary to control water inflow through the construction if in-pit dewatering systems such as dewatering wells, drainage ditches, sumps, pipelines, and pumps.
An allowance has been included in the open pit capital and operating costs for in-pit dewatering through in-pit sumps.
The range of monthly average flow rate was estimated at 23.9-81.6 L/s for the West pit and 18.1-64.4 L/s for the East Pit.
Booster pumps are expected to be required when the pits pass the 160 m.
Open Pit Slope Design
Bench Height
The bench height is a direct function of the excavation equipment type and size planned for the open pit mine. The open pit design considered a 5m operational bench height in initial studies, with a triple bench (15 m) for the final pit wall and long period pushbacks. Therefore, the geotechnical study considered this geometrical constraint as the bench height.
Berm Width
The berm width must be wide enough to contain falling blocks, narrow enough to not significantly affect the overall slope angle and not increase the strip ratio substantially or disrupt operations. The berm width suggested for this study is 7.5 m wide, considering the final bench height of 15 m.
Pit Sectorization
The proposed open pit design was divided into five geometrical sectors. As the main slope direction within some sectors has shown considerable variations, they were divided into subsectors. Ten sections were drawn up in the mine geotechnical domains to verify the factor of safety (FoS) of the operational pit on an overall scale.
Flow Sheet:
Crusher / Mill Type | Model | Size | Power | Quantity |
Jaw crusher
|
|
1.0m x 1.3m
|
|
1
|
Cone crusher
|
|
1.32m
|
|
2
|
Ball mill
|
|
5.2m x 7.9 m
|
3.5 MW
|
1
|
Summary:
Primary Crushing and Stockpiling
The crushing circuit is designed for an annual operating time of 5,631 hours or 64% availability at a capacity of 4,000 tpd. ROM ore is transported from the mine to the process plant by haul trucks. The ROM bin is fitted with a static grizzly to keep large oversize rocks from blocking the primary crusher. A vibrating grizzly feeder ahead of the of the primary jaw crusher is used to screen out fine material and feed the jaw crusher. The primary crusher product combines with the grizzly feeder undersize and is conveyed to a secondary screen. Screen oversize is fed to a secondary cone crusher and the secondary crushed product is fed to the tertiary screen. The tertiary crusher operates in closed circuit with a tertiary screen. The combined undersize from both the secondary and tertiary screens is conveyed to the mill feed stockpile with 80% of the particle size distribution passing an aperture of 10 mm. The mill feed stockpile is equipped with two belt feeders to regulate feed at 181 t/h into the ball mill via a feed conveyor. Each feeder is capable of feeding the plant at design capacity independently.
The material handling and crushing circuit includes the following key equipment:
• ROM Bin;
• Vibrating grizzly;
• Fixed rock breaker;
• Primary jaw crusher, 1 m x 1.3 m;
• Secondary screen;
• Secondary cone crusher, 1.32 m diam. head;
• Tertiary Screen;
• Tertiary shorthead cone crusher, 1.32 m diam. head;
• Crushed ore reclaim belt feeders (equipped with VSDs);
• Conveyors;
• Metal detection and rejection.
Grinding Circuit
The grinding circuit consists of a ball mill in closed circuit with hydrocyclones. The circuit is sized based on ball mill feed size of 80% passing 10 mm and product of 80% passing 100 µm. Mill feed from the stockpile is reclaimed by two belt feeders. The feeders transfer the mill feed onto the ball mill feed conveyor which discharges the ore directly into the ball mill feed chute. Process water is added to the ball mill feed chute to create a slurry in the ball mill. The mill feed chute also receives oversized material from the gravity scalping screen and the underflow from the hydrocyclone cluster. The mill is operated in closed circuit where the product is discharged into a common pumpbox with independent pumps for both the hydrocyclone cluster and the gravity circuit. The mill discharge includes a trommel for scat removal. Ground material that is too coarse will be classified by the hydrocylone and will report back to the ball mill for further size reduction.
The hydrocyclone classification circuit will operate at a nominal circulating load of 400% which is a typical for the design cyclone overflow density and target grind size. The cyclone cluster is configured to achieve a target design cyclone overflow product sizing of 80% passing of 100 µm. Leach testing showed that this product size is sufficient to achieve design recoveries of gold. The cyclone cluster will have pneumatically actuated valves that allow automated feed pressure control as well as manually actuated isolation valves for maintenance. Process water is also added to the cyclone feed pumpbox to obtain the appropriate density prior to pumping to the cyclones. Cyclone overflow is sent to a trash screen prior to the leaching circuit to remove any large detritus that may accumulate in the leach tanks. The ball mill cyclone pumpbox is also equipped with a second pump which discharges slurry to the gravity concentration circuit where gravity gold is concentrated and treated.
The grinding circuit includes the following key equipment:
• 3,500 kW, 5.2 m diam. X 7.9 m EGL ball mill with a single pinion drive;
• Cyclone feed pumpbox;
• Classification cyclones;
• Cyclone feed pump, gravity feed pump;
• Trash screen.
Processing
- Gravity separation
- Dewatering
- Filter press plant
- Intensive Cyanidation Reactor (ICR)
- Carbon re-activation kiln
- Centrifugal concentrator
- Concentrate leach
- Agitated tank (VAT) leaching
- Carbon in pulp (CIP)
- Elution
- Carbon adsorption-desorption-recovery (ADR)
- Solvent Extraction & Electrowinning
- Cyanide (reagent)
Flow Sheet:
Summary:
Key operating criteria for the process plant are:
• Nominal throughput of 4,000 t/d or 1.46 Mtpa;
• Crushing plant availability of 64%;
• Plant availability of 92% for grinding, leach plant, and gold recovery operations.
The process design is comprised of the following circuits:
• Three stage crushing of ROM material;
• A covered, crushed ore stockpile to provide buffer capacity ahead of the grinding circuit;
• A ball mill with cyclone classification;
• Gravity concentration and intensive leaching of the concentrate;
• Trash screening;
• Leach + carbon adsorption (L/CIP);
• Acid washing of loaded carbon and Pressure Zadra type elution followed by electrowinning and smelting to produce doré;
• Carbon regeneration by rotary kiln;
• Cyanide destruction of tailings using SO2/air process;
• Arsenic precipitation;
• Tailings thickening.
Gravity Circuit
The gravity circuit is fed from a dedicated ........

Recoveries & Grades:
Commodity | Parameter | Avg. LOM |
Gold
|
Recovery Rate, %
| 95.8 |
Gold
|
Head Grade, g/t
| 2.26 |
Reserves at December 15, 2021:
The Open Pit Mineral Reserves and Mineral Resources are reported at a CoG of 0.45 g/t gold.
Category | Tonnage | Commodity | Grade | Contained Metal |
Probable
|
15,798,900 t
|
Gold
|
2.26 g/t
|
1,150,200 oz
|
Measured
|
7,680,000 t
|
Gold
|
2.756 g/t
|
680,518 oz
|
Indicated
|
7,988,000 t
|
Gold
|
2.886 g/t
|
741,220 oz
|
Measured & Indicated
|
15,668,000 t
|
Gold
|
2.822 g/t
|
1,421,738 oz
|
Inferred
|
975,000 t
|
Gold
|
2.113 g/t
|
66,237 oz
|
Corporate Filings & Presentations:
Document | Year |
Corporate Presentation
|
2022
|
...................................
|
2021
|
...................................
|
2021
|
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