Overview
Stage | Production |
Mine Type | Open Pit |
Commodities |
|
Mining Method |
|
Processing |
- Gravity separation
- Smelting
- Agitated tank (VAT) leaching
- Carbon in leach (CIL)
- AARL elution
- Solvent Extraction & Electrowinning
- Cyanide (reagent)
|
Mine Life | 2022 |
Latest News | Avesoro Resources Inc. - Pit Wall Failure at New Liberty October 3, 2019 |
Source:
p. 4
Company | Interest | Ownership |
Government of Liberia
|
10 %
|
Direct
|
Avesoro Resources Inc.
|
90 %
|
Indirect
|
Bea Mountain Mining Corp.
|
90 %
|
Direct
|
Avesoro Resources Inc. holds its interests in the New Liberty Gold Mine through its subsidiary Bea Mountain Mining Corporation (“Bea”). On July 29, 2009 Bea was granted a Class A Mining Licence (“Bea Mining Licence”) within the Bea Mountain Mineral Development Agreement property (the “Bea MDA Property”) by the Government of Liberia (“GoL”). The Bea Mining Licence permits mining within the 478 km2 area which encompasses the New Liberty Gold Mine. The GoL holds a 10% free carry interest in the Bea Mining Licence.
Summary:
The vast majority of the mineralisation at the Project is hosted within the altered parts of the sheared ultramafic rocks. Pyrrhotite and arsenopyrite are the main sulphides with occasional pyrite and rare chalcopyrite or pentlandite. The areas with the highest gold grades are associated with arsenopyrite. Metallurgical tests of the mineralised sections carried out by Lakefield Research Limited (Lakefield, 1999b) indicated that the gold is free in form. Gold mineralisation occurs in zones of variable thickness, with average widths of 10 m, and is nearly continuous along 2 km of strike.
Gold at the Project is linked with an assemblage of sulphides and oxides in ultramafics and granite. Opaque minerals include trace to minor quantities of pyrrhotite, arsenopyrite, chalcopyrite, pentlandite, galena, sphalerite, magnetite, ilmenite and rutile. Sulphide growth may be in the form of vein fills, massive aggregates, clusters, blebs, stringers and fine or coarse disseminations in ultramafics or granite veins. There appears to be a progression from syntectonic to late-tectonic growth, with at least two phases of sulphide and oxide growth. The non-opaque minerals are amphibole, chlorite, mica, serpentine, talc and quartz. Pyrrhotite, arsenopyrite, coarse grained pyrite, chalcopyrite, sphalerite and minor pentlandite are the principal sulphides; the chief observation being (but not always) an increase in grain size and abundance, both absolute and relative, in host rocks near granite veins.
The gold mineralisation at the Project is associated with sulphides, hosted in metamorphosed ultrabasic rocks intruded by tourmaline-bearing granites that are closely associated with albitite dykes. The ultramafics consist of amphibole (tremolite, actinolite), chlorite, phlogopite, talc, some carbonate and the sequence is moderately to highly silicified.
The widespread silicification is accompanied by ubiquitous magnetite precipitation. The sulphide association is pyrrhotite, pyrite (the two alternating in dominance), arsenopyrite and minor- to-trace chalcopyrite, niccolite and gersdoffite. Magnetite and minor haematite are the main oxides
The mineralisation being targeted by Aureus comprises typical Upper Archaean to Lower Proterozoic greenstone belt-hosted lode gold mineralisation. These deposits are often referred to as orogenic and are characterised by the presence of a combination of gold-quartz veins and disseminated mineralisation.
Archaean orogenic deposits are typically hosted in greenstone belts comprising meta-volcano sedimentary supracrustal assemblages, together with coeval calc-alkaline granitoid intrusions. The gold mineralisation is typically hosted in moderate to steeply dipping quartz-dominated shear zones with associated extensional vein systems and is considered to be coeval with the syntectonic stages of the orogeny and related to periods of crustal shortening at 8 km -15 km depth. Structures are typically formed at, or close to, contacts between rock types of contrasting competencies, and mineralisation is often localized at bends or splay intersections in the shear system.
Summary:
The mining operations are based on conventional drill-and-blast, load and haul mining techniques. Loading of the ore and waste rock following drill-and-blast will be undertaken by hydraulic excavators in backhoe configuration into nominal 100 tonne Komatsu HD 785 haul trucks with 50% of the ore reporting directly to the crusher tip and 50% to the ROM ore pad, and waste to the designated waste dump areas. It is has been assumed that the weathered portion of the ore and waste is free dig or requires some local ripping and as it transitions to fresh rock, blasting will be required.
All waste material will report either to the surface waste dumps which wrap around the open pit or be backfilled in the mined-out pit areas of the Larjor pit, depending on which facility is closest and available at the time of mining, and to suit the efficient scheduling of the mining fleet. Before any waste is backfilled into Larjor, an underground mining study will be undertaken to assess the potential of mining the deeper, down plunge high-grade ore shoots. In the early stages of the Pre-Strip and mining phases, waste rock will be used to construct a protective drainage berm, which wraps around the open pit between the waste rock dumps.
Flow Sheet:
Processing
- Gravity separation
- Smelting
- Agitated tank (VAT) leaching
- Carbon in leach (CIL)
- AARL elution
- Solvent Extraction & Electrowinning
- Cyanide (reagent)
Flow Sheet:
Summary:
The original process plant was designed, built and commissioned in July 2015 by DRA, an international engineering company, to treat 1.1 million tonnes per annum of ore, corresponding to a mill feed of 146 t/hour.
The process flowsheet is an industry-standard arrangement consisting of crushing, ore stockpiling, grinding and classification, gravity gold recovery, thickening and gold extraction by cyanidation in a Carbon-in Leach (CIL) circuit. Gold is recovered from the activated carbon by acid washing, elution and electowinning, followed by smelting to produce gold doré. The CIL tailings undergo cyanide detoxification followed by arsenic precipitation from tailings solution prior to disposal in the tailings dam.
Recoveries & Grades:
Commodity | Parameter | 2018 | 2017 | 2016 |
Gold
|
Recovery Rate, %
| 88 | 89 | 83.2 |
Gold
|
Head Grade, g/t
| 2.73 | 2.39 | 2.82 |
Production:
Commodity | Units | 2018 | 2017 | 2016 |
Gold
|
oz
| 109,707 | 76,179 | 63,556 |
All production numbers are expressed as metal in doré.
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Operational Metrics:
Metrics | 2018 | 2017 | 2016 |
Total tonnes mined
| 23,149 kt | 14,102 kt | 9,961 kt |
Ore tonnes mined
| 1,352 kt | 1,166 kt | 996 kt |
Waste
| 21,797 kt | 12,935 kt | 8,965 kt |
Stripping / waste ratio
| 16.1 | 11.1 | 9 |
Tonnes processed
| 1,411 kt | 1,144 kt | 842 kt |
Plant annual capacity
| | 1.1 Mt | |
Reserves at December 31, 2018:
Category | OreType | Tonnage | Commodity | Grade | Contained Metal |
Proven
|
In-Situ (OP)
|
0.216 Mt
|
Gold
|
1.65 g/t
|
11 koz
|
Probable
|
Stockpiles
|
0.21 Mt
|
Gold
|
1.47 g/t
|
10 koz
|
Probable
|
In-Situ (OP)
|
4.701 Mt
|
Gold
|
3.19 g/t
|
482 koz
|
Proven & Probable
|
Stockpiles
|
0.21 Mt
|
Gold
|
1.47 g/t
|
10 koz
|
Proven & Probable
|
In-Situ (OP)
|
4.917 Mt
|
Gold
|
3.12 g/t
|
494 koz
|
Measured
|
In-Situ (OP)
|
0.19 Mt
|
Gold
|
1.82 g/t
|
10.9 koz
|
Indicated
|
In-Situ (OP)
|
4.48 Mt
|
Gold
|
3.49 g/t
|
503 koz
|
Measured & Indicated
|
In-Situ (OP)
|
4.67 Mt
|
Gold
|
3.42 g/t
|
513.9 koz
|
Inferred
|
In-Situ (OP)
|
0.03 Mt
|
Gold
|
1.7 g/t
|
2 koz
|
Commodity Production Costs:
| Commodity | Units | 2018 | 2017 | 2016 |
Cash costs (sold)
|
Gold
|
USD
|
862 / oz
|
918 / oz
|
1,688 / oz
|
All-in sustaining costs (sold)
|
Gold
|
USD
|
1,120 / oz
|
1,427 / oz
|
1,930 / oz
|
Operating Costs:
| Units | 2017 |
OP mining costs ($/t mined)
|
USD
| 2.68 |
Financials:
| Units | 2018 | 2017 | 2016 |
Revenue
|
M USD
| 140.3 |
95.2
|
63.6
|
After-tax Income
|
M USD
| -40.3 |
-20.8
|
-103
|
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