Source:
p. 9
Summary:
The Farim phosphate deposit is located within the Middle Eocene Lutetian Formation that forms part of the southern margin of the Mauritania-Senegal- Guinea Cenozoic sedimentary basin.
The Farim phosphate deposit is a flat-lying sedimentary phosphatic bed, which underlies an area in excess of 60 km2.
Sandy-argillaceous overburden with soft, alternating sandy, clayey and sandy-clayey layers:
- Phosphatic interval (FPO);
- Upper dolomitic limestone;
- Decarbonised phosphate unit (FPA) corresponding to the Saliquinhé phosphate deposit;
- Calcareous phosphate member (FPB);
- Limestone at the footwall of the phosphate sequence, white, soft and porous.
Overburden.
The overburden waste at Farim typically consists of a layer of reddish brown laterite gravel, followed by cream coloured clay with occasional cobbles and boulders of cemented orange sand and brown clay. This is followed by a layer of stiff brown to orange sandy clay and a layer of firm light grey, moist, high plasticity clay of a similar thickness. No laboratory test results are currently available for these materials.
The thickness of the overburden layers range from less than 20 m to over 40 m in the mining areas, whereas the phosphate matrix layer which is also a sedimentary deposit ranges from less than 2 m in thickness to over 5 m thick in places. Below these two layers is a soft rock limestone layer which increases quickly with depth to medium and hard bedrock.
FPO.
The FPO is a clayey dolomitic limestone that is weakly phosphatic and has limited economic potential. It comprises laminated green clays and aluminophosphate and is 0.5 m to 1 m thick. At the surface in the higher zones, laterite with a ferruginous cover in places may be found.
The FPA phosphate matrix is homogenous and has a grainstone texture, with grains less than 800 µm in size. It is a soft, poorly cemented unit of phosphatic sand, which includes phosphatised shell and bone material, teeth, faecal pellets and crustacean coprolites. There is no calcareous cement and it contains little silica and clay. It is mildly indurated and includes siliceous or pyritised layers 5 to 20 cm thick which comprise an average of 6% of the unit. The FPA layer has a P2O5 content of approximately 30% (consistently higher than 25%). The FPA unit is currently considered the potentially economic phosphate horizon.
The FPA is localised within the Saliquinhé bay sub-basin and is the potentially economic phosphate bed. The sub-basin is bounded to the south and east by carbonate platform rocks against which the FPA wedges out. The north- western limit of the FPA has not yet been defined. To the north, the Tambato submarine bar, which formed a barrier between the Saliquinhé bay and the deeper Casamance basin, will likely form the northern limited of the FPA unit but this has not been demonstrated by drilling.
The limits of the FPA unit, the hanging and the foot walls, are clearly defined. A mixture of saprolitic fine sand and clays, which are generally unconsolidated, overlies the FPA. The immediate hanging wall to the FPA is 20 to 60 cm thick unconsolidated sand. The hanging wall rocks are oxidised reddish brown to an elevation of about 10 m below sea level. The FPA is grey to beige and brown and lies in a generally reducing environment below the oxidised interval. This is important because iron oxide, which is soluble in sulphuric acid, is a contaminant in phosphate deposits whereas iron sulphide, which is insoluble in sulphuric acid, is not.
The FPA unit has an average width of about 3 m (in the resource area) and underlies an area of about 60 km2 . In the northern part of the basin, north of the village of Saliquinhé, a northeasterly trending area about 5.5 km long and 1.5 km wide has FPA thickness typically greater than 3.0 m and up to 6.0 m. A smaller area to the south of Saliquinhé, near the Cacheu River, also exceeds 3.0 m in thickness.
FPB.
The FPB is a calcareous phosphate unit consisting of alternating soft phosphate strata with carbonaceous gangue and thinner, hard strata of slightly phosphatic bioclastic limestone. The lower grade FPB layer consists of highly carbonated phosphate, generally containing 5% to 20% P2O5 with an average of 13% P2O5. The FPB phosphatic limestone is indurated and much harder than FPA.
FPB is located immediately below FPA, but exists under only 50% of the area of FPA. FPB also has a large extent outside of FPA. This horizon is known to extend 20 km north to south and 50 km east to west with thickness variable from 1 to 15 m with an average thickness of approximately 5.3 m.
Summary:
The site contains a high-grade sedimentary, flat-lying phosphate deposit located within a single phosphate matrix bed known as the FPA matrix zone.
The FPA (Decarbonized phosphate unit) matrix is mined by a multiple bench open pit haul back mine using excavators and trucks. Golder selected the excavator/truck mining method based on lower initial capital, lower investment risk, increased grade control, limited power supply, and flexibility to adapt to a smaller scale Direct Shipping Option (DSO) operation if needed.
For the 1.75 million tonnes per annum (Mtpa) (dry basis) open pit, it is planned that overburden will be stripped and removed with 12 cubic metre (m3 ) front end loaders (FEL) or other similar excavator matched with 97 tonne (t) capacity haul trucks. The matrix will be mined with 5 m3 bucket class backhoes matched with 36 t capacity trucks to minimize mining dilution and maximize matrix recovery. The matrix will be hauled to a 175,000 t (dry basis) ROM stockpile adjacent to the plant, and segregated by quality. The matrix will be reclaimed and carefully blended into a ROM Bin by front-end wheel loaders with 12 m3 buckets to achieve the desired product P2O5 grade. The plant feed hopper will be installed so that matrix haul trucks can directly feed matrix to the plant if possible.
Because of the concentrated annual rainfall from July through September, the mine plan limits mining activities at full production to nine months out of the year; the other three months will be mined at reduced productivity. Operations must be vigilant with in-pit dewatering to prevent pit flooding and maintain pit stability.
The remote nature of the Farim operation, with limited power supply, precludes the use of electric mining equipment. All mining equipment selected for the plan is diesel mobile equipment.
Summary of Mine Plan parameters:
- Permanent wall angle - 20°:
- Permanent wall operational - FOS >1.3:
- Bench Height - 10 m:
- Short-Term Bench Face (Batter) Angle - 65°:
- Short-Term Berm Width - 14.9 m:
- Long-Term Bench Face (Batter) Angle (After Sloughing) - 25°:
- Long-Term Berm Width (After Sloughing) - 6.5 m:
- Overburden angle of repose WD/IOB/SOS - 1V:4H / 1V:6H / 1V:6H:
- Overburden spoil swell factor 27%:
- Total Moisture (As-Received Basis), Overburden - 20%:
- Overburden Density (As-Received Basis) - 2.10 t/m3:
- Overburden Density (Dry Basis) - 1.68 t/m3:
- Total Moisture (As-Received Basis), Matrix - 0%;
- Matrix Density (As-Received Basis) - 1.75 t/m3:
- Matrix Density (Dry Basis) - 1.40 t/m3:
- Minimum mineable matrix thickness - 1 m:
- Mining roof loss - 100 mm:
- Mining floor dilution - 75 mm:
- Buffer between pit and river - 100 m;
- Full production mining months per year - 9 months:
- Reduced production mining months per year 3 months.
The overall 20° permanent slope angle is the controlling factor for the slope recommendations. The temporary dig face angle of 65 degrees is an assumed typical temporary slope angle cut by an excavator or loader that, over time, will slough and erode to a flatter slope angle. The benches in the higher cohesion clay soils will maintain steeper bench faces over the lifetime of the pit wall. Near surface soils may be expected to have additional cohesion from laterite formation and cementation by iron oxides. Cohesionless sand will reach flatter bench face angles over time. The intent of the slope design is to maintain an effective safety bench through the duration of the phased final pit walls. The 25° permanent bench face angle represents the minimum expected long term bench face angle and provides a 6.5-m wide safety bench.
Processing
- Vacuum filtration
- Desliming
- Dewatering
Flow Sheet:
Summary:
The process description details the 1.75 Mtpa beneficiation plant for the production of 1.32 Mtpa of phosphate concentrate.
ROM will be delivered by 36 tonne dump trucks from the open pit. ROM will either be dumped directly into the ROM Bin or dumped onto the ROM stockpile. The ROM stockpile will have a five weeks storage capacity equivalent to 175,000 live tonnes.
ROM ore (P80 25 mm) will be dumped by haul trucks or loaded by wheel loaders directly into the ROM Bin. The ROM Bin will be equipped with a static grizzly to prevent oversized rocks from entering the bin. A belt feeder will extract ROM rock from the bin to be conveyed to the horizontal scrubber.
For metallurgical accounting and plant control purposes, weightometers will be installed on the scrubber feed conveyor.
The scrubbing and sizing circuit will include a horizontal scrubber, an attrition scrubber, two reject screens, two-stage desliming cyclones, two hydrosizers, and a clas ........

Recoveries & Grades:
Commodity | Parameter | Avg. LOM |
Phosphate rock
|
Recovery Rate, %
| 75.5 |
Phosphate rock
|
Head Grade, %
| 30 |
Phosphate rock
|
Concentrate Grade, %
| 34 |
Projected Production:
Commodity | Units | Avg. Annual | LOM |
Phosphate rock
|
kt
| 1,321 | 33,225 |
All production numbers are expressed as concentrate.
Operational Metrics:
Metrics | |
Waste tonnes, LOM
| 418,680,000 bcm * |
Ore tonnes mined, LOM
| 44,007 kt * |
Annual processing capacity
| 1.75 Mt * |
Annual ore mining rate
| 1.75 Mt * |
* According to 2015 study.
Reserves at September 14, 2015:
Mineral Resources and Mineral Reserves have not been revised since 2015 year.
Category | Tonnage | Commodity | Grade | Contained Metal |
Proven & Probable
|
44 Mt
|
P2O5
|
30 %
|
13.2 Mt
|
Measured & Indicated
|
105.6 Mt
|
P2O5
|
28.4 %
|
30 Mt
|
Inferred
|
37.6 Mt
|
P2O5
|
27.7 %
|
10.4 Mt
|
Mine Management:
Job Title | Name | Phone | Profile | Ref. Date |
.......................
|
.......................
|
.......................
|
|
Jun 16, 2022
|
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