Overview
Stage | Pre-Feasibility |
Mine Type | Open Pit |
Commodities |
|
Mining Method |
|
Processing |
- Smelting
- Agitated tank (VAT) leaching
- Carbon in pulp (CIP)
- AARL elution
- Carbon adsorption-desorption-recovery (ADR)
- Solvent Extraction & Electrowinning
- X-Ray sorting
- Cyanide (reagent)
|
Mine Life | 13 years (as of Jan 1, 2019) |
Underperformance of the project and higher operating costs led to the mine being closed and placed on care and maintenance on November 14, 1997. Because the Mt Todd site was not reclaimed when the mine closed, the dumps and heap leach pad require ongoing care and maintenance, which company provides. |
Latest News | Vista Gold Drilling Confirms North Extension of the Batman Core Zone at the Mt Todd Gold Project January 21, 2021 |
Source:
p. 32
Vista and its subsidiary, Vista Gold Australia Pty Ltd (Vista Australia) entered into an agreement to acquire an interest in the Project located in NT, Australia on March 1, 2006. The acquisition was completed on June 16, 2006 when the mineral leases comprising the Project were transferred to Vista Australia and funds held in escrow were released. Vista Australia is the operator of the Mt Todd property.
Deposit Type
- Vein / narrow vein
- Orogenic
- Intrusion related
Summary:
The Batman and Quigleys gold deposits of the Mt Todd Mine are formed by hydrothermal activity, concomitant with retrograde contact metamorphism and associated deformation, during cooling and crystallization of the Tennysons Leucogranite and early in D2.
The deposits are similar to other gold deposits of the porphyry copper gold (PCG) and are classified as orogenic gold deposits in the subdivision of thermal aureole gold style. The Batman deposit shares some characteristics with intrusion-related gold systems, especially in terms of the association of gold with bismuth
and reduced ore mineralogies. This makes the deposit unique in the PCG.
The geology of the Batman deposit consists of a sequence of hornfelsed interbedded greywackes, and shales with minor thin beds of felsic tuff. Bedding is striking consistently at 325°, dipping at 40° to 60° to the southwest. Minor lamprophyre dykes trending north-south pinch and swell, cross cutting the bedding.
Northerly trending quartz sulfide veins and joints striking at 0° to 20°, dipping to the east at 60° are the major location for mineralization in the Batman deposit. The veins are 1 millimeter (mm) to 100 mm in thickness with an average thickness of around 8 mm to 10 mm. The veins consist of dominantly quartz with sulfides on the margins. The veining occurs in sheets with up to 20 veins per horizontal m. These sheet veins are the main source of mineralization in the Batman deposit.
A variety of mineralization styles occur within the Mt Todd area. Of greatest known economic significance are auriferous quartz-sulfide vein systems. These vein systems include the Batman, Jones, Golf, Quigleys and Horseshoe prospects, which occur within a north-northeast trending corridor, and are hosted by the Burrell Creek Formation. Tin occurs in a north-northwest trending corridor. The tin mineralization comprises cassiterite, quartz, tourmaline, kaolin, and hematite bearing assemblages, which occur as bedding to parallel breccia zones and pipes. Polymetallic Au, W, Mo, and Cu mineralization occurs in quartz-greisen veins within the Yinberrie Leucogranite; a late stage highly fractionated phase of the Cullen Batholith. The Batman Deposit extends approximately 2,200 m along strike, 400 m across dip and drill tested to a depth of 800 m. Drilling indicates the Batman mineralization to be open along-strike and down-dip.
The mineralization within the Batman deposit is directly related to the intensity of the north- south trending quartz sulfide veining. The lithological units impact on the orientation and intensity of mineralization.
Sulfide minerals associated with the gold mineralization are pyrite, pyrrhotite and lesser amounts of chalcopyrite, bismuthinite and arsenopyrite. Galena and sphalerite are also present, but appear to be postgold mineralization, and are related to calcite veining in the bedding plains and the east-west trending faults and joints.
Two main styles of mineralization have been identified in the Batman deposit. These are the north-south trending vein mineralization and bedding parallel mineralization.
The Quigleys deposit mineralization has a distinctive high-grade shallow dipping 30°-35° northwest shear zone extending for nearly 1 km in strike and 230 m vertical depth within a zone ofmore erratic lower grade mineralization.
Summary:
The truck and shovel method provides reasonable cost benefits and selectivity for this type of deposit. Only open-pit mining methods are considered for mining at Mt Todd.
Open pit ore totals 208 Mt grading 0.84 g/t and contains 5.6 Moz of gold. Open pit production will have a 2.5:1 strip ratio over the 13-year LoM. Upon completion of conventional mining, the existing heap leach pad will be processed.
Processing
- Smelting
- Agitated tank (VAT) leaching
- Carbon in pulp (CIP)
- AARL elution
- Carbon adsorption-desorption-recovery (ADR)
- Solvent Extraction & Electrowinning
- X-Ray sorting
- Cyanide (reagent)
Flow Sheet:
Summary:
The flowsheet consists of primary crushing, closed circuit secondary crushing, closed circuit tertiary crushing using high pressure grinding rolls (HPGRs), ore sorting, two-stage grinding, cyclone classification, pre-leach thickening, leach and adsorption, elution electrowinning and smelting, carbon regeneration, tailings detoxification and disposal to conventional tailings storage facility (TSF).
Process recovery was determined based on ore types. Three ore types, sulfide, mixed, and oxide were identified for the open pit and will have recoveries of 92.9%, 91.8%, and 91.5%, respectively. The heap leach pad will have a recovery of 90.7%. An additional 1% for net solution loss is applied to all the deposits and heap leach which results in a LoM average recovery of 91.9%.
The run of mine ore from the pit is expect to have a maximum particle size of 1000 mm and F80 to the primary crusher of 400 mm. Two stages of crushing, primary and secondary are required to reduce ........

Recoveries & Grades:
Commodity | Parameter | Avg. LOM |
Gold
|
Recovery Rate, %
| ......  |
Gold
|
Head Grade, g/t
| 0.82 |
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Reserves at September 10, 2019:
Category | Tonnage | Commodity | Grade | Contained Metal |
Proven
|
72,672 kt
|
Gold
|
0.88 g/t
|
2,057 koz
|
Probable
|
148,369 kt
|
Gold
|
0.79 g/t
|
3,791 koz
|
Proven & Probable
|
221,041 kt
|
Gold
|
0.82 g/t
|
5,848 koz
|
Measured
|
78,182 kt
|
Gold
|
0.88 g/t
|
2,210 koz
|
Indicated
|
219,209 kt
|
Gold
|
0.8 g/t
|
5,608 koz
|
Measured & Indicated
|
297,391 kt
|
Gold
|
0.81 g/t
|
7,817 koz
|
Inferred
|
62,923 kt
|
Gold
|
0.72 g/t
|
1,464 koz
|
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