Source:
p. 3, 17
Deposit Type
- Vein / narrow vein
- Orogenic
- Mesothermal
Summary:
Specifically, the Nampala deposit can be classified as a turbidite-hosted structurally controlled orogenic (mesothermal) lode-gold system.
Gold mineralization is primarily hosted in competent coarse-grained sedimentary rock where brittle fracturation, openings and veining occurred. Gold is associated to structurally controlled tension quartz vein systems and stockworks developed in the brittle fractures and in areas of increased porosity as a result of the deformation of the more competent coarse-grained greywacke, siliciceous sandstone and sandstone.
Shear zones are developed in the more ductile adjacent (or locally intercalated) shales (particularly the graphitic shale) and are commonly barren. Some narrow NNE-trending subvertical shear corridors are exposed in the pit from north to south and have been traced nearly continuously to the southernmost drill hole of the 2017-2018 drilling program.
Some anomalous gold values can also be found locally in the chill margins or along the contact of the intermediate intrusives. Local brittle deformation seems to have created space for tension quartz veins to penetrate the fringe of the stock and this seems to be confirmed by resistivity and conductivity geophysical maps which display what seem to be a slight NE/SW and NW/SE fracture pattern. This corresponds to the general orientation of the mineralization in the mine where mineralized domains are oriented 020°N and are controlled laterally by subvertical structures and stratigraphy. Within these delineations, as many as five generations of veins are observed and there seems to be a global plunge of 25-30° to the SW as well as the SE where flatter undulating quartz veins are noted. The mineralization type found at the Main and East zones is structurally controlled sediment-hosted orogenic gold affected by late intrusives. In both zones, the mineralized quartz veins have propagated into the more competent coarsegrained wakes, sandstones and arenites affected by brittle deformation. Through rheological contrasts between the different sediments, the plastic planar shear slipping along the ductile and less permeable siltstones and mudstones resulted in the propagation of interplanar shear bands, the brittle fracturing of arenitic rocks, the opening of tension jogs and the formation of dilation joints. As a result, quartz vein propagation and hydrothermal alteration of the protolith was favourable in the more porous sandstones and arenitic rocks. Hydrothermal alteration and quartz vein development patterns follow the structural corridors, filling extension gashes and jogs along shear corridors in the sediments and along the intrusives.
The dominant hydrothermal alteration in both zones is characterized by pervasive carbonatization-silicification and pyrite- arsenopyrite disseminations accompanied by chlorite and clay minerals (kaolinitization). The hydrothermal alteration displays outward zonation around quartz veins. The bulk of the sulphides occur as widespread disseminations of fine (submillimetre) pyrite and arsenopyrite. They are found within silicate-carbonate alteration rims in the wall rock around individual quartz veins, within quartz-carbonate veins. The degree of silicification and arsenopyrite concentrations appear to be slightly higher in the East Zone than in the Main Zone.
Summary:
The Nampala Mine is excavated using a conventional truck and shovel operation. The widest equipment used by the contractors is a Caterpillar 773B haul truck matched with a 385 hydraulic excavator. The ore and waste are composed mostly of saprolite located in the oxidized horizon. No drilling and blasting are required to access the current Mineral Reserve. A total of 7 pits are planned to recover the identified Mineral Reserve.
The pit designs follow closely the Pit Shell provided by the pit optimizer when evaluating the Mineral Reserve and the pit design parameters. The access ramp centerline follows mostly the Pit Shell of the Mineral Reserve. For operational purposes, only openings identified by the optimizer which are wider than 100 m in diameter are converted to pit designs.
Pit design parameters:
- Ramp Grade - 10%;
- Bench height - 10 m;
- Minimum catch bench width - 5 m;
- Maximum face angle - 70o;
- Design face angle - 67o;
- Maximum pit slope - 45o;
- Minimal opening diameter - 100 m.
The ore body is subvertical and located predominantly in the center of each pit. This allows the access ramps to be positioned mostly in the waste to avoid leaving ore in the pit walls. Also, since the Lower Transition material is not part of the Mineral Reserve, it is left in place in the lower part of the pit. This constrains the pit design along the near-horizontal boundary between the Upper Transition and the Lower Transition. The flat surface grants easy access to the Oxide and Upper Transition located at the lowest levels of the pits. The previously enumerated elements constitute the base for the mining recovery assumption of 97%.
The 2020 MRE provides a grade for each block based on 2m assay composites that are not constrained by the lithology contact. Also, the mine operation has set in place a rigorous ore control process to lower dilution. In addition, the orebody is subvertical, presents generally a large width and does not require intensive blasting prior to excavation. The previous points allow us to assume that the dilution from mining operation is marginal. From that hypothesis, the Mineral Resource block model dilution required to reflect mining operation is deemed very small thus set at 0%.
The mine operation is subject to weather conditions. During the raining season, heavy rains may render the mine access road slippery and inaccessible. Thus, under those conditions, the mill feed is provided from the ROM pad only. To account for the yearly mining production reduction due to rain, a total of 12 days are considered lost: 2 days in July, 4 days in August, 4 days in September and 2 days in October. Considering the above, the mine is in operation 353 days per year.
The ROM pad size is targeted at 250,000 t including a low grade stockpile near the ROM Pad to provide for sufficient blending capabilities and a fallback plan in case of unforeseen problems.
Flow Sheet:
Crusher / Mill Type | Model | Size | Power | Quantity |
Cone crusher
|
|
|
|
1
|
Sizer
|
|
|
|
1
|
Ball mill
|
|
|
|
1
|
Processing
- Calcining
- Gravity separation
- Carbon re-activation kiln
- Smelting
- Agitated tank (VAT) leaching
- Carbon in leach (CIL)
- Elution
- Carbon adsorption-desorption-recovery (ADR)
- Solvent Extraction & Electrowinning
- Cyanide (reagent)
Flow Sheet:
Summary:
The proposed Nampala process plant design is based on conventional and wellknown CIL technology. The process plant will consist of scrubbing, crushing, milling, cyanidation by carbon in leach, Zadra elution method (used for recovery of gold from loaded carbon), electrowinning, carbon regeneration, calcining, smelting and tailing disposal. The plant comprises also reagent mixing, storage and distribution facilities, water, air supplies and infrastructures.
Recoveries & Grades:
Commodity | Parameter | 2020 | 2019 | 2018 | 2017 | 2016 | Avg. LOM |
Gold
|
Recovery Rate, %
| ......  | ......  | 85.6 | 83.9 | 80.3 | 88 |
Gold
|
Head Grade, g/t
| ......  | ......  | 0.94 | 0.85 | 0.82 | 0.7 |
Production:
Commodity | Units | 2021 | 2020 | 2019 | 2018 | 2017 | 2016 |
Gold
|
oz
| ...... ^ | ......  | ......  | 44,946 | 36,997 | 12,051 |
All production numbers are expressed as metal in doré.
^ Guidance / Forecast.
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Operational Metrics:
Metrics | 2020 | 2019 | 2018 | 2017 | 2016 |
Ore tonnes mined
| ......  | 1,873,721 t | 1,797,809 t | 1,451,497 t | 680,621 t |
Waste
| ......  | 3,458,443 t | 2,951,212 t | 2,184,546 t | 1,613,814 t |
Stripping / waste ratio
| ......  | 1.8 | 1.6 | 1.5 | 2.4 |
Tonnes processed
| ......  | 1,909,663 t | 1,795,591 t | 1,615,966 t | 719,090 t |
Daily processing rate
| ......  | | | 4,400 t | |
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Reserves at July 31, 2020:
The Mineral Reserve was estimated using cut-off of 0.28 g/t in the Oxide and 0.31g/t in the Lower Transition.
The Mineral Resource was estimated using cut-off of 0.25 g/t in the Oxide, 0.33 g/t in the Transition and 0.31 g/t in the Fresh Rock.
Category | Tonnage | Commodity | Grade | Contained Metal |
Probable
|
17,147 kt
|
Gold
|
0.71 g/t
|
391 koz
|
Indicated
|
37,887 kt
|
Gold
|
0.71 g/t
|
869 koz
|
Inferred
|
2,989 kt
|
Gold
|
0.69 g/t
|
66 koz
|
Total Resource
|
40,876 kt
|
Gold
|
0.71 g/t
|
936 koz
|
Corporate Filings & Presentations:
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News:
News | Date |
Robex: 2021 Sustainable Growth Strategy Validation and 2022 New Dimension Resulting From the Business Combination With Sycamore
|
May 2, 2022
|
Robex Resources Inc.: Excellent December Performance Continuing Into January
|
January 21, 2022
|
Robex Resources Inc.: 2021 Third Quarter Results — Increase in Production and New Mine Plan
|
November 26, 2021
|
Robex Resources Inc.: Acquisition of “Gladie” Permit and Beginning of Production for Four New Pits
|
March 30, 2021
|
Robex Resources Inc.: With 391,000 Ounces of Probable Mineral Reserves, Robex Expects a Mine Life of Nearly 9 Years for Nampala
|
October 25, 2020
|
Robex Resources Inc. Modifies the Released NI 43-101 Technical Report on August 9, 2019
|
June 5, 2020
|
Robex Resources Inc. Announces the First Encouraging Results of the 2020 Exploration Program.
|
May 22, 2020
|
Robex Resources: Nampala Project (Mali) - New Resource and Reserve Estimate
|
June 25, 2019
|
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