The Analytical Fingerprint of conflict minerals (TTT) – Focus on “coltan” (tantalum) ores. Dr. Frank Melcher Tervuren, Dec.02, 2010 for the AFP working group of the BGR: T. Graupner, M. Sitnikova, T. Oberthür, F. Henjes-Kunst, H.-E. Gäbler, S. Goldmann and C. Savu-Krohn, G. Rantitsch (MU Leoben), A. Gerdes (U Frankfurt), H. Braetz (U Erlangen), S. Dewaele (RMCA)
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The Analytical Fingerprintof conflict minerals (TTT) –
Focus on “coltan” (tantalum) ores.Dr. Frank Melcher
Tervuren, Dec.02, 2010
for the AFP working group of the BGR:T. Graupner, M. Sitnikova, T. Oberthür, F. Henjes-Kunst, H.-E. Gäbler, S. Goldmann
and C. Savu-Krohn, G. Rantitsch (MU Leoben),A. Gerdes (U Frankfurt), H. Braetz (U Erlangen), S. Dewaele (RMCA)
AFP – a method to fingerprint the originof conflict minerals
• Tantalum / “coltan”• The basics of the fingerprint: mineralogy and chemical
composition of coltan• Tantalum in Africa• Methods to fingerprint tantalum ores• How does it work?• Tin (and tungsten)• Summary and Outlook
Tantalum ore/ “coltan”
Gatumbadistrict,Rwanda
Buranga Ruhanga
Nyarigamba
Coltan & tin mining in Africa
0
50
100
150
200
250
300
350
400
450
1995 1997 1999 2001 2003 2005 2007 2009
Namibia
Uganda
Tant
alum
[t]
Mozambique
ZimbabweCongo, DR
Rwanda
BurundiNigeria
Ethiopia
Coltan boom
Tantalum mine production in Africa
Source: USGS, BGR data base
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Coltan: trade name, used in Central Africa for tantalum – niobium oresand concentrates, mainly columbite – tantalite (Fe,Mn)(Nb,Ta)2O6
Tantalum ores: in concentric, zoned “rare-metal“ pegmatites
• Variable Mg, Li, REE• high Sn, Ti, W, Zr• Low Sc, Bi
• REE patterns• Commonly flat, unfractionated• Usually no Eu anomaly (Eu*Md = 1.7; range 0.1-100)• Occasionally positive Ce anomalies (Ce*Md = 0.9; range 0.01-13)
Kibaran rare-element pegmatites
Katanga
0,01
0,1
1
10
100
1000
10000
La Ce Pr Nd Sm Eu Gd Tb Dy Y Ho Er Tm Yb Lu
Sam
ple/CI
0,01
0,1
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10
100
1000
10000
100000
La Ce Pr Nd Sm Eu Gd Tb Dy Y Ho Er Tm Yb
Sample/CI
Nuweibi, Somalia
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0,1
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100
1000
10000
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La Ce Pr Nd Sm Eu Gd Tb Dy Y Ho Er Tm Yb Lu
Sam
ple/
CI
Kibaran, Katanga
Nigeria Egypt, Somalia
LA – ICPMS: Trace elements in CGM
Tantalite Valley
0,1
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La Ce Pr Nd Sm Eu Gd Tb Dy Y Ho Er Tm Yb Lu
Sam
ple/
CI
Tantalite Valley, Namibia
Concentrate
Polished section
SEM / MLA
Methods of the fingerprint for tantalum ores
LA-ICP-MS
FEI Quanta FEGESEM
FinniganElement 2
SF-ICP-MS193 nm Excimer
laser
Equipment BGR
EPMAnot routinely,
occasionally only
Parameters
Mineralogy ofconcentrate (quantitative)
Composition of CGM-Major elements-Trace elements
U-Pb age
Polishing Laboratory
Rehwald polishing machine
Scanning electron microscope / Mineral Liberation Analysis
• Ranks tested for 16 elements• 120 concentrate data sets• p = rankits• Test sample correctly classified
Mines FARDC
Centre de Negoce
Mines FDLR
Mines CNDP
Mines Mayi Mayi
Mines FLF
Mine d'or
Mine de coltan
Mine de cassiteriteMine de wolframite
Mine de diamant
Mine de manganese
Mine Pilote
Legend
Nyabiondo
Kanyabayonga
Kipese
Manguredjipa
Kamituga
Pounia
Lubutu
Kalima
Kailo
Mubi
Baraka
Bisie Mpama
Kalimbi (Nyabibwe)
Manguredjipa
Misisi - Akyanga
Mukungwe
Lulingu
0.25 0 0.25 0.5
degrees
WGS 84
Scale 1:10
MINISTERE DES MINES RDCGISEMENTS DES MINERAIS DE CONFLIT
SITUATION DE SECURITE
AVRIL 04, 2010
UWE NAEHER; BGR
Will the analytical fingerprint have a positive influence on the situation inthe eastern DRC?
Uwe Näher (BGR) and CEEC
CEEC cataster• 84 locs coltan• 217 locs Sn
Multivariate statistics and Machine learning Software
Confusion matrix to distinguish measurements(grains) from localities east (Rwanda) and west(Kivu) of the rift valley, depending on λ as aresult of a randomized cross-validation.λ gives the distribution of allocation accuracies
East West
EastWest
Kivu Provinces
Rwanda
Mineral chemistry
Error-validated classification
0.001
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Zr+W (ppm)
Rwanda(Kibaran)
Katanga(Kibaran)
Maniema and Kivu(Kibaran)
Trace element chemistry of CGM
Ituri: >1.9 Ga
Cassiterite samples – Kivu-Region
Rutongo
Cassiterite: LA-ICP-MS trace elementsN = 50 measurements per field
Cassiterite: LA-ICP-MS analysis
Bisie,DRC
Rutongo, Rw
1) Ta / Sn / W provinces in Africa are distinguished based on modalmineralogy, age and geochemistry of ore minerals (columbite-tantalite, cassiterite, wolframite)
2) Ta-Sn pegmatites and Sn-W veins of Central Africa have• roughly the same age (930-990 Ma, “Kibaran”)• similar host rocks (metapelites, amphibolites, granitoids)• similar genesisbut they differ in• mineralogy and mineral chemistry
3) Fingerprinting the origin of TTT ores is feasible- from regional scale down to deposit scale - using ore concentrates
Results (1)
The analytical fingerprint (AFP) of coltan ores:
Application (1): “Positive certification” – “Fraternity test”Identify the origin of a tantalum ore concentrate by comparisonwith a standard data base of samples from known locations(AFP sensu strictu)
Application (2):Identify samples of mixed origin (more than one,with end members present in the data base)
Application (3): “Forensic method”Estimate the origin (tantalum province, district, mine) of anunknown sample with no data present in the data base