Overview
Stage | Feasibility |
Mine Type | Open Pit & Underground |
Commodities |
|
Mining Method |
- Truck & Shovel / Loader
- Sub-level stoping
- Longhole open stoping
- Backfill
|
Processing |
- Gravity separation
- Carbon re-activation kiln
- Dewatering
- Intensive Cyanidation Reactor (ICR)
- Smelting
- Flotation
- Carbon in leach (CIL)
- Carbon adsorption-desorption-recovery (ADR)
- Elution
- Solvent Extraction & Electrowinning
- Cyanide (reagent)
|
Mine Life | 9 years (as of Jan 1, 2021) |
Latest News | St Barbara completes Bardoc acquisition April 27, 2022 |
Source:
p. 2
On 13 April 2022, St Barbara completed the acquisition of all the issued shares of Bardoc Gold through the implementation of a scheme of arrangement (Scheme). The new St Barbara shares issued under the Scheme commenced trading on 14 April 2022.
Summary:
The deposit occurs on the eastern limb of a narrow NNW trending structure, the Bardoc-Broad Arrow syncline within the Bardoc Tectonic Zone. In this zone the sequence comprises highly deformed fault slice lenses of intercalated Archaean mafic and ultramafic volcanics and metasediments.
Gold mineralisation is predominately hosted within a 300 to 400m wide differentiated dolerite emplaced into the mafic/ultramafic-sediment sequence. The geological setting, structure and style of gold mineralisation show a distinct similarity to that seen at Paddington and the Broad Arrow deposits 12 to 16km to the south.
The Zoroastrian dolerite is thought to be the stratigraphic equivalent of the Paddington dolerite which hosted the 1m+ ounce mine at Paddington itself with both deposits bounded to the west by the Black Flag sediments and to the east by the Mount Corlac ultramafics. Shear zones up to 10m wide containing gold bearing laminated quartz veining (5cm to 1m wide) occur on both contacts.
The Zoroastrian South has been the main focus of drilling since the discovery of the stockwork system within the granophyric unit. Here drilling has been conducted beneath a series of historical shallow workings on narrow quartz veins resulting in the discovery of a large body of gold mineralisation at depth.
The Slug Hill/Breakaway area at Zoroastrian South represents a distinct magnetic/gravity high that appears to be folded (or boundinaged) with closure to the south. Sediments and high magnesium basalts/ultramafics are clearly seen in outcrop but have not been intersected and/or identified in drilling beneath the outcrop. Drilling instead has intersected a differentiated dolerite with a granophyric unit hosting gold mineralisation associated with arsenopyrite rich quartz stockwork/breccia. The magnetic high is instead related to a pyrrhotite rich zone within the dolerite with the gold mineralisation occurring predominately within and adjacent to its margins. 3D modelling suggests that the magnetic zone has a similar 30-40 degree plunge to the north similar to the gold mineralisation.
Mining Methods
- Truck & Shovel / Loader
- Sub-level stoping
- Longhole open stoping
- Backfill
Summary:
UNDERGROUND
The Project consists of two underground mines, Zoroastrian and Aphrodite. The Zoroastrian mine is planned to commence off the southern end of the existing Zoroastrian central pit and is the priority focus due to the high-grade, free-milling nature of the ore, and the ability to rapidly commence mining activities. The Aphrodite Underground extends from the base of the Aphrodite Stage 1 Pit. Both underground mines will extract ore from multiple lode systems which are open in all directions. Additional lodes are expected to be encountered as underground mining progresses with progressive underground exploration drilling, currently cost prohibitive from surface.
DESIGN OVERVIEW
Gold is estimated and reported within the underground models to be evaluated within the processing and financial summaries. All ore planned to be extracted from the mines is contained within fresh rock. In order to determine the economically mineable part of the resource, the total value of the gold mineralised material was calculated.
ZOROASTRIAN UNDERGROUND
The Zoroastrian Underground is located at, and will be accessed off, the southern end of the existing Zoroastrian Central Pit.
The underground mine is designed to be accessed off a portal from the southern end of the existing Zoroastrian pit. Lateral development will be carried out using conventional mechanised drill and blast techniques, using twin-boom jumbos.
Stoping will be carried out via a top-down mining method using conventional mechanised sub-level longhole open stoping techniques, utilising rib and sill pillars for void stability and dilution control. Level spacing for the stoping is 20m floor-to-floor with typical 15.5m up-dip stope heights. No fill is designed to be used, although where benefit may be realised to reduce trucking requirements, filling may be implemented.
APHRODITE UNDERGROUND
Mining at Aphrodite is proposed to commence following the completion of the Stage 1 pit, which will provide an adequate location to commence a decline portal in fresh and competent rock material. Based on this, Bardoc will prioritise mining of the Aphrodite Stage 1 pit for the commencement of underground activities at Aphrodite as early as possible.
The underground mine is designed to be accessed off a portal from the northern end of the proposed Aphrodite Stage 1 Pit. Lateral development will be carried out using conventional mechanised drill-andblast techniques, using twin-boom jumbos.
Stoping will be carried out via a top-down mining method using conventional mechanised sub-level longhole open stoping techniques, utilising rib and sill pillars for void stability and dilution control. Level spacing for the stoping is 20m floor-to-floor with typical 15.5m up-dip stope heights. No fill is designed to be used, although where benefit may be realised to reduce trucking requirements, filling may be implemented.
OPEN PIT MINING
The Bardoc open pits consist of the Excelsior, Zoroastrian, Aphrodite, Bulletin South and Mayday open pits, which will be mined using conventional open pit mining methods. It is proposed for the larger pits that 190- tonne excavators will be used with a fleet of 90-tonne dump trucks.
Open pit mining is planned on a double-shift continuous roster basis, using both a 120-tonne and a 190- tonne excavator loading 90-tonne dump trucks, with mining benches approximately 5m in height.
The 120 tonne excavator fleets are expected to commence the open pit mining of the Zoroastrian North and Bulletin South pits. 190 tonne excavator fleets will be utilised to commence the Excelsior and Aphrodite pits to service the initial waste stripping, after which each of the projects will transition back to 120 tonne excavator fleets. All other pits will utilise the 120 tonne excavator fleets.
Flow Sheet:
Crusher / Mill Type | Model | Size | Power | Quantity |
Jaw crusher
|
|
|
|
1
|
Pebble crusher
|
|
|
132 kW
|
1
|
SAG mill
|
|
6.7m x 4.7m
|
4100 kW
|
1
|
Ball mill
|
|
5.5m x 8.7m
|
4100 kW
|
1
|
Summary:
The circuit comprises of:
• Primary Jaw crushing capable of operating at a nominal rate of 300 t/h (based on 80% availability). The crusher product size is targeted at 80% passing 125mm to provide suitable lump size for autogenous grinding;
• A surge bin with cast off radial stacker conveyor to generate separate refractory and free milling stockpiles;
• A SAG mill which is a 6.7m (IS) diameter by 4.7m (EGL) long and powered by a 4,100kW variable speed motor. A polyurethane trommel screen will remove oversize and direct them to the pebble crushing circuit;
• A pebble crusher with a 132kW motor and operated with a closed sized setting of 13mm, which discharges into the SAG mill feed conveyor;
• A Ball mill which is a 5.5m (IS) diameter by 8.7m (EGL) long and powered by a 4,100kW variable speed motor. A 12mm aperture polyurethane trommel screen will remove oversize and deposit it into the scats bunker;
Processing
- Gravity separation
- Carbon re-activation kiln
- Dewatering
- Intensive Cyanidation Reactor (ICR)
- Smelting
- Flotation
- Carbon in leach (CIL)
- Carbon adsorption-desorption-recovery (ADR)
- Elution
- Solvent Extraction & Electrowinning
- Cyanide (reagent)
Flow Sheet:
Summary:
PROCESS PLANT
The Bardoc Processing Plant is designed to treat both free-milling and refractory ore. The plant will be designed for construction in two stages. Stage 1 will consist of CIL processing, while Stage 2 is an upgrade to include the flotation and dewatering circuits to treat the Aphrodite refractory material to be mined in year 2. Concentrate generated from the flotation circuit will be sold into a concentrate sale agreement as described in Section 2.
The Bardoc Stage 1 Processing Plant has been designed to treat free-milling ore from multiple sources. The plant design is based on a nominal throughput of 2.1 Mtpa The mill throughput rate, based on 8,000 operating hrs per annum (91.3% availability), is 262.5 t/h. The comminution circuit is designed for processing the harder fresh ore. When processing a blend that includes oxide and transitional a higher throughput will be achieved. The downstream circuit design allows this higher throughput.
Recoveries & Grades:
Commodity | Parameter | Avg. LOM |
Gold
|
Concentrate Grade, g/t
| 66.1 |
Gold
|
Recovery Rate, %
| 95.5 |
Gold
|
Head Grade, g/t
| 2 |
Projected Production:
Commodity | Product | Units | Avg. Annual | LOM |
Gold
|
Concentrate
|
kt
| | 292 |
Gold
|
Metal in doré
|
koz
| | 505 |
Gold
|
Metal in concentrate
|
koz
| | 593 |
Gold
|
Metal in conc./ doré
|
koz
| 136 | 1,097 |
Operational Metrics:
Metrics | |
Stripping / waste ratio
| ......  |
Waste tonnes, LOM
| ......  |
Ore tonnes mined, LOM
| ......  |
Tonnes processed, LOM
| ......  |
Annual processing capacity
| ......  |
* According to 2021 study.
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Reserves at March 29, 2021:
Category | Tonnage | Commodity | Grade | Contained Metal |
Probable
|
15,874 kt
|
Gold
|
2 g/t
|
1,007 koz
|
Measured
|
152 kt
|
Gold
|
2.3 g/t
|
11 koz
|
Indicated
|
36,338 kt
|
Gold
|
1.7 g/t
|
2,044 koz
|
Inferred
|
18,063 kt
|
Gold
|
1.8 g/t
|
1,018 koz
|
Total Resource
|
54,597 kt
|
Gold
|
1.8 g/t
|
3,073 koz
|
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