Overview
Stage | Production |
Mine Type | Underground |
Commodities |
|
Mining Method |
|
Processing |
- Intensive Cyanidation Reactor (ICR)
- Gravity separation
- Centrifugal concentrator
- Agitated tank (VAT) leaching
- Carbon in leach (CIL)
- Elution
- Solvent Extraction & Electrowinning
- Cyanide (reagent)
|
The Mount Belches comprises Maxwells, Cock-eyed Bob and Santa underground mines. Mining activities were prioritised and focussed primarily at the higher-grade Cock-eyed Bob and Maxwells mines. |
Latest News | Santa comes early for Silver Lake October 25, 2019 |
Source:
p. 67
Deposit Type
- Banded iron formation hosted
Summary:
MAXWELLS
The Maxwells deposit is hosted within the lower ‘Maxwells’ member. The Mount Belches group is located in the southern Eastern Goldfields Superterrane, Yilgarn Craton, Western Australia.
The iron formation is a silicate/oxide-facies unit with over printing sulphides, which has undergone metamorphism (upper-greenschist facies) and deformation (two generations of folds). The gold deposits are hosted in both the hinge zone and along the limbs of a regional scale, chevron folded BIF package.
Gold dominantly occurs as inclusions of native gold and/or electrum within or around pyrrhotite, magnetite, and arsenopyrite, and economic mineralisation is typically restricted to the BIF horizons.
The Maxwells resource extent consists of 2020m strike; 440m across strike; and 790m down dip and open at depth.
COCK-EYED BOB
The Cock-eyed Bob is hosted within the upper ‘Santa Clause’ member of the Banded Iron-Formation (BIF) of the Mount Belches group. The Mount Belches group is in the southern Eastern Goldfields Superterrane, Yilgarn Craton, Western Australia.
The iron formation is a silicate/oxide-facies unit with over printing sulphides and has undergone metamorphism (upper-greenschist facies) and deformation (two generations of folds). The gold deposits are hosted in both the hinge zone and along the limbs of a regional scale, chevron folded BIF package.
Gold dominantly occurs as inclusions of native gold and/or electrum within or around pyrrhotite, magnetite, and arsenopyrite, and economic mineralisation is typically restricted to the BIF horizons.
The Cock-Eyed Bob complex’s resource extent consists of 1150m strike; 700m across strike; and 700m down dip and open at depth.
SANTA
The ‘Maxwells’, CEB and ‘Flora Dora’ deposits are hosted within the lower ‘Maxwells’ member of The Mount Belches group and the ‘Santa’ deposit is hosted within the upper ‘Santa’’ member both members are located in the southern Eastern Goldfields Superterrane, Yilgarn Craton, Western Australia.
The iron formation is a silicate/oxide-facies unit with over printing sulfides and has undergone metamorphism (upper-greenschist facies) and deformation (two generations of folds). The gold deposits are hosted in both the hinge zone and along the limbs of a regional scale, chevron folded BIF package.
Gold dominantly occurs as inclusions of native gold and/or electrum within or around pyrrhotite, magnetite and arsenopyrite, and economic mineralisation is typically restricted to the BIF horizons.
The Santa resource extent consists of about 2900m strike; 900m across strike; and 500m down dip and open a depth.
Summary:
MAXWELLS
Longhole open stoping was selected as the mining method for Maxwells. Diluted stopes shapes above the cutoff grade were created. Stopes were then excluded from the Reserve by the following criteria:
-Stopes above the 1219mRL
-Isolated stopes which could not support access development
-Stopes which intersected the open pit or part of crown pillar.
Decline and level development was designed to ensure each stope could be accessed. Maxwells is a vertical narrow orebody. Longhole stoping is a standard mining method for vertical narrow orebodies.
Assumptions regarding geotechnical parameters are based on design parameters recommended by an external consultant. A hydraulic radius of 9 was determined to be a stable stope span (40mH x 43mL). The assumptions used to determine the minable shapes was a minimum ore width of 1m wide plus the dilution on each wall of 0.5m. A 16mH x 10mL stope dimension was also applied to determine the mineable shapes above the cut-off grade.
Mining recovery factor of 85% was applied to account for ore loss in pillars and unplanned ore loss. A haulage decline and ventilation decline/rises have been designed.
COCK-EYED BOB
Longhole open stoping was selected as the mining method for Cock-eyed Bob. Diluted stopes shapes above the cut-off grade were created. Isolated which could not support access development stopes were then excluded from the Reserve.
Decline and level development was designed to ensure each stope could be accessed. Mining recovery (85%) was then applied to account for ore left in support pillars and unplanned ore loss.
Cock-eyed Bob is a vertical narrow orebody. Longhole stoping is a standard mining method for vertical narrow orebodies.
Assumptions regarding geotechnical parameters are based on design parameters and mining from the 1420 to 1125 levels between 2011 and 2021. A hydraulic radius of 7.4 was determined to be a stable stope span (48mH x 28mL).
The assumptions used to determine the minable shapes was a minimum ore width of 1m wide plus the dilution on each wall of 0.5m. A 16mH x 10mL stope dimension was also applied to determine the mineable shapes above the cut-off grade.
Mining recovery factor of 85% was applied to account for ore loss in pillars and unplanned ore loss. A haulage decline and ventilation rises have been designed.
SANTA
Underground
Longhole open stoping was selected as the mining method for Santa. Diluted stopes shapes above the cut-off grade were created. Stopes were then excluded from the Reserve by the following criteria:
-Isolated stopes which could not support access development
-Stopes which intersected the open pit or part of crown pillar.
Santa is a near vertical orebody. Longhole stoping is a standard mining method for vertical orebodies. Assumptions regarding geotechnical parameters are based on design parameters recommended by the onsite Geotechnical Engineer. The assumptions used to determine the minable shapes was a minimum ore width of 3 metres wide plus the dilution on each wall of 0.5m. A 20mH x 10mL stope dimension was also applied to determine the mineable shapes above the cut-off grade.
The Santa underground operation will be paused in Q1 FY22 following exploration success which identified a potential cut back to the historical Santa open pits and provided further definition to Santa underground Mineral Resources at depth.
open pit
The Santa open pit is a cut-back to the existing Santa, Flycamp and Santa Craze pits. The proposed Santa Open Pit is to be operated using conventional excavate, load and haul methods. These methods have been used previously at Santa and the current Aldiss open pit operations. The pit design is based double lane ramps to within 50m of the pit floor. A minimum mining width of 20m is designed in areas of the cut-back to allow enough room for the mining equipment to operate.
Processing
- Intensive Cyanidation Reactor (ICR)
- Gravity separation
- Centrifugal concentrator
- Agitated tank (VAT) leaching
- Carbon in leach (CIL)
- Elution
- Solvent Extraction & Electrowinning
- Cyanide (reagent)
Source:
Summary:
Mount Belches Mining Centre feeds the 1.3Mtpa Randalls mill.
Santa, Cock-eyed Bob and Maxwells ore have been processed previously by Silver Lake Resources between 2011 and 2021 from open pit and underground operations at the Randall Gold Processing Facility (Carbon in Leach process). The mineralogy of the ore has not changed with depth. The metallurgical recovery is well understood, and no metallurgical issues were present during the previous processing of the Santa ore. A metallurgical recovery of 95% has been applied.
Recoveries & Grades:
Commodity | Parameter | 2021 | 2020 | 2019 |
Gold
|
Head Grade, g/t
| ......  | ......  | ......  |
Production:
Commodity | Units | 2021 | 2020 | 2019 | 2018 | 2017 |
Gold
|
koz
| ......  | ......  | ......  | 45 | 26 |
All production numbers are expressed as metal in ore.
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Operational Metrics:
Metrics | 2021 | 2020 | 2019 | 2018 |
Ore tonnes mined
| ......  | ......  | 376,153 t | 270,176 t |
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Reserves at June 30, 2021:
The adopted cut-off grades 1.0 g/t and 2.0 g/t for reported mineral resource. A reserve cut-off grade of 2.7g/t. (MAXWELLS).
The adopted cut-off grades 1.0 g/t and 2.0 g/t for reported mineral resource. A reserve cut-off grade of 2.3g/t (COCK-EYED BOB).
The adopted cut-off grades 1.0 g/t and 2.0 g/t for reported mineral resource. A reserve cut-off grade of 2.0g(SANTA).
Category | Tonnage | Commodity | Grade | Contained Metal |
Proven
|
298 kt
|
Gold
|
4.9 g/t
|
47 koz
|
Probable
|
5,551 kt
|
Gold
|
1.8 g/t
|
320 koz
|
Proven & Probable
|
5,849 kt
|
Gold
|
2 g/t
|
367 koz
|
Measured
|
681 kt
|
Gold
|
6 g/t
|
131 koz
|
Indicated
|
10,800 kt
|
Gold
|
2.9 g/t
|
1,011 koz
|
Inferred
|
3,637 kt
|
Gold
|
3.2 g/t
|
371 koz
|
Total Resource
|
15,118 kt
|
Gold
|
3.1 g/t
|
1,513 koz
|
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