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Mineralogy and mineral processing of carbonatite-hosted REE and P2O5 at Songwe Hill, Malawi
Frances Wall1 Richard Pascoe1 William Dawes2 Aoife Brady2
1 Camborne School of Mines, University of Exeter, UK 2 Mkango Resources Ltd, Calgary, Canada
Safaa Al Ali1
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Outlines
Importance of REE and P2O5
The Study area (Songwe Hill)
Aims of the study
Chemistry of the deposits
Mineralogy of the deposits
Mineral processing tests
Conclusions
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Application of Rare Earth Elements
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REE Wind
turbines Vehicles Lighting
Fluid Cracking Catalysts
Polishing Powders
Auto Catalysts
Magnets Magnets Batteries Phosphors La ● ● ● ● ● Ce ● ● ● ● ● Pr ● ● ● ● Nd ● ● ● ● ● ● Sm ● ● Eu ● Tb ● Dy ● ● Y ●
Ceramics, 5%
Pigments, 1% Phosphors,
7%
Batteries, 8%
Al and Mg
alloys, 1%
Iron and Steel, 6%
Polishing, 12%
Glass, 12%
Catalysts, 20%
Mgnets, 19%
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Phosphate rock mine
Phosphate concentrate
Production of phosphoric acid
Production of phosphate fertilisers
MAP, TSP, NP, NPK & other fertilisers
Sulphuric acid
Ammonia
Importance of P2O5
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Songwe Hill Carbonatite
Legend
Google earth image shows the Songwe Hill area, Malawi.
Mauze (nepheline syenite)
The Songwe Hill carbonatite Chilwa Alkaline Province Late Jurassic/early Cretaceous.
Study area
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Geological Map with drill hole collars and traces * Indicated mineral reserve of 13.2mt, grading 1.62% at 1.5% TREO cut-off grade * Inferred mineral reserve of 18.6mt, grading 1.38 at 1% TREO cut-off grade.
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Aims of the study
1. Perform chemical analyses to identify major, minor and rare earth elements in all samples
2. Identify and quantify the mineralogy of carbonatite deposits liberation and association.
3. Undertake selected laboratory mineral processing experiments to separate apatite and synchysite. Carbonatite rock
Phosphate fertiliser Rare earth elements
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0
5
10
15
20
25
30
35
40
PX013 PX022b PX5+15 PX021 PX033 PX035 PX012 PX09
Conc
etra
tions
%
Sample number
CaO
FeO
SiO2
P2O5
Concentration major oxides in Songwe ore samples.
Rare earth oxide concentrations in Songwe ore samples.
Chemistry of the deposits
10
100
1000
10000
REO
Con
cent
ratio
n pp
m
Rare earth oxides
PX013
PX022b
PX5+15
PX021
PX033
PX035
PX012
PX09
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XRD profiles of all the crushed core Carbonatite samples.
Lin
(Cou
nts)
X-ray diffraction profiles
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Apt
Feld
rutile
SEM/EDS observations
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First stage separation at 3, 6.3, 10.9 and 16.4 Amp.
Second stage separation at 3, 6.3, 10.9 and 16.4 Amp.
Non-magnetic
Magnetic Feed pulp
Final magnetic Final Non-magnetic
Schematic of two-stage separation on WHIMS completed at CSM
Mineral processing tests
Flow sheet test work was completed at Mintek in South Africa
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0
5
10
15
20
25
30
35
40
45
3 6.3 10.9 16.4
Wei
ght r
ecov
ery
(g)
Magnetic field (Amps)
Mag
Non-mag
Weight recovery of the separated fractions at various magnetic fields
Wet high intensity magnetic separation results
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0.25
0.35
0.45
0.55
0.65
0.75
0.85
0.95
1.05
1.15
3 5 7 9 11 13 15 17
Gre
ade
%
Magnetic fields (Amps)
Magnetic products P2O5 BaO Sr Ce La
0.35
0.55
0.75
0.95
1.15
1.35
1.55
1.75
1.95
3 5 7 9 11 13 15 17
Gra
de %
Magnetic fields (Amps)
Non-magnetic products P2O5 BaO Sr Ce La
0
5
10
15
20
25
30
35
40
45
3 6 9 12 15 18
Rec
over
y %
Magnetic fields (Amps)
Magnetic products P2O5 La Ce
50556065707580859095
100
3 6 9 12 15 18
Rec
over
y %
Magnetic fields (Amps)
Non-magnetic products P2O5 La Ce
The grades and recovery of the P2O5, BaO, Sr, Ce and La in (A) the magnetic and (B) non-magnetic products as a function of magnetic field strength
Wet high intensity magnetic separation results
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Conclusions
Ankerite and calcite are the main predominant gangue minerals.
The target ore minerals are apatite which hosts the phosphorous and HREE and synchysite-(Ce) which hosts the LREE.
All RE-minerals are associated with all gangue minerals (especially, ankerite and calcite) in different proportions.
the only finer grinds can be done to separate apatite and synchysite minerals successfully as they occurred as fine grains.
Good results obtained at 6.3 Amp with grade 1.94% and recovery 84% of P2O5 in the non-magnetic products -63 μm, but still 0.80% is reported at magnetic product.
Further work is needed with very fine milled feed samples at P80 -38 μm at 6.3 Amp.
XRD is not qualified technique to identify the ore minerals in the current samples.
It seems that apatite is better to be recovered using WHIMS while synchysite needs more grinding to be more liberated and then separate it.
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Thanks for listening