The Analytical Fingerprint of conflict minerals (TTT ... · The Analytical Fingerprint of conflict...
Transcript of The Analytical Fingerprint of conflict minerals (TTT ... · The Analytical Fingerprint of conflict...
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
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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
GSWA, Mineral Resources Bulletin 22 (2004)
Nb>TaTa>Nb
CGM =columbite-tantalite-
group minerals
(Fe,Mn)(Nb,Ta)2O6
Regional zoning patterns of“rare-metal“ pegmatites
Behaviour of tantalum-niobium minerals in pegmatites
CGM chemistry:• variation within deposit
• variation within single crystals• fractionation trends
Fractionatio
nKibeke Pangi, DRC
Columbite-Fe
Columbite-Fe
• Columbite-Tantalite (CGM) (Fe,Mn)(Ta,Nb)2O6 orh• Magnocolumbite Mg(Nb,Ta)2O6 orh• Tapiolite series (Fe,Mn)(Ta,Nb)2O6 tetr• Ixiolite group (Ta,Nb,Sn,Fe,Ti)4O8 orh• Wodginite group (Mn,Sn,Fe,Ti)Ta2O6 mcl• Stibiotantalite Sb(Ta,Nb)O4 orh• Bismutotantalite Bi(Ta,Nb)O4 orh• Pyrochlore group A1-2B2O6(O,OH,F) cub
• A = Ca, K, Ba, Y, Ce, Pb, U, Sr, Cs, Na, Sb, Bi, Th• B = Ta, Nb, Ti, Sn, Fe, W (microlite)
• Euxenite (Y,REE,U,Pb,Ca)(Nb,Ta,Ti)2(O,OH)6• Strüverite, Ilmenorutile (Ta,Nb,Fe,Ti)O2• …and many more
Coltan - Mineralogy
1) Kibaran2) Ituri3) Alto Ligonha4) Adola Belt5) Nigeria6) Damara7) Namaqualand8) West Africa9) Egypt10) Zimbabwe
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Important Tantalum Provinces in Africa
Burundi
Rwanda
Uganda
DRC
Kibaranca
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- 100
0 M
a
> 1900 Ma
• Coltan in Kibaran (ca. 1000 Ma)and Archean to Paleoproterozoicpegmatites (>2000 Ma)
• Niobium in younger carbonatites
KibaranDRC
KivuManiemaKatangaIturi
RwandaBurundiUganda
Ituri
Lueshe
Central African coltan provinces
Ituri
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100*Mn/(Mn+Fe)
100*Ta/(Ta+Nb)
Ituri provinceDRC-CAR craton, northern DR Congo• Investigated: Enehe, Mambasa, Lubero• artisanal production• Model ages: 2000-2500 Ma• Mineralogy: columbite-(Fe), tantalite-(Fe),
tapiolite, (Pb-U-)microlite• Cassiterite, wolframite were mined in the area• Geochemistry of CGM
•high Ti, W, Zr, Hf, U, Th, Pb, As, Mg, Sc,Y, REE
• low Sn• REE: variable slopes, moderate negative Eu
anomalies (Eu*Md = 3.5)
Ituri
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La Ce Pr Nd Sm Eu Gd Tb Dy Y Ho Er Tm Yb Lu
Sample/CI
DRC, Rwanda, Burundi, Uganda
• >100 samples, >75 locations• Production ca. 500 t Ta2O5
• Formation ages: ca. 930 - 1000 Ma• Mineralogy: columbite-(Fe-Mn), tantalite-(Fe-Mn), tapiolite, wodginite, microlite,
uranmicrolite, cassiterite, wolframite• rare euxenite, bismutotantalite, foordite, thoreaulite, rankamaite, simpsonite etc.• Geochemistry of CGM
• 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
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Nuweibi, Somalia
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Kibaran, Katanga
Nigeria Egypt, Somalia
LA – ICPMS: Trace elements in CGM
Tantalite Valley
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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
Scanning electron microscope / Mineral Liberation Analysis
Bijyojo, Ruanda Pangi, Kongo
Mineralogy mode Grain sizes Grain shapes Intergrowths
AFP in practice
Step 1: calculate a U-Pb age from LA-ICP-MS data→ Attribute the sample to a “coltan age province“
e.g.: U-Pb ageCGM = 900-1000 Ma
Kibaran
Namaqualand
SveconorwegianGrenvillian
AFP in practice
Step 2: mineralogical composition→ discriminate a group of deposits based on the presence of specific heavy minerals
prerequisite: minerals are not easily removable by classification methods
>2 cas
>1 tap>1 wdg
>1 tap<1 wdg
>1 Umc <1 Umc >5 tap
>1 UMc <1 UMc
>0.5 SE >0.5 SE
1-5 tap
<1 tap>1 wdg
<1 tap<1 wdg
>1 Umc <1 Umc
Age group “Kibaran“ <2 cas
cas = Cassiteritetap = Tapiolite wdg = Wodginite/IxioliteUmc = Uran-Microlite + MicroliteSE = SEE-Ta-oxides
Example: Kibaran coltan
AFP in practice
Step 3: chemical composition of CGM (or other ore minerals)
• Acquire a dataset for >50 grains from a concentrate• One analysis per grain• Major (Mn, Fe, Nb, Ta) and trace elements (>40 elements)
• Data are stored in a SQL Database, together with details on locationand textures
• Statistical tests identify the origin (the match with a datasetcontained in the database)
• → “Fraternity test”!
Wilcoxon-Mann-Whitney (rank-sum) test for unrelated medians
Chemical data of columbite-tantalite minerals from concentrate samples ofknown origin
Sample No Country Origin Sum of all pNumber of
indistinguishable parameters p (TiO 2) MnO SnO 2
unknown20122 CD Manono 12,460 0 0,96016 0,86365 0,75723303 CD Manono 5,958 0 0,56684 0,89533 0,89839119 CD Manono 5,012 0 0,1264 0,00252 0,7512123 CD Manono 4,371 0 0,23149 0,00409 0,67873301 CD Manono 4,088 0 0,42674 0,11731 0,02867644 CD Comptoir in Goma 3,473 0 0,00133 0,00656 0,0867392 CD Manono 3,040 0 0,07318 0,66473 0,95679390 CD Manono 1,732 0 0,057 0,15822 0,58536734 RW Gatumba (plant) 1,579 0 0,69338 0,00014 0,62013118 CD Manono 3,813 1 0,04019 0,79862 0,04177388 CD Manono 3,811 1 0,42414 0,13943 0,04085384 CD Manono 3,573 1 0,2931 0,06403 0,0000548 RW Gatumba (plant) 2,119 1 0,12071 0,00001 0,2103650 RW Gatumba (plant) 1,958 1 0,03006 0,00918 0,0109988 RW Nyarigamba 1,844 1 0,00043 0,20333 0,00028
136 RW Nemba 7,442 2 0 0,59082 0,8224349 RW Gatumba (plant) 3,958 2 0,47405 0,00004 0,16968
174 RW Rutsiro (plant) 3,606 2 0 0,17055 0,01127109 CD Yubili Riv., Kivu 3,591 2 0,04739 0,01129 0,00083209 RW Nemba 3,082 2 0,00017 0,00392 0,172244 CD Mapimo Mulungu, Nzovu 2,769 2 0,69061 0 0,0002884 RW Ruhanga A 4,616 3 0,01527 0,00225 0,95342
• 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
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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: 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
Results (2)
Vision: Regional certification system
ColtanDRC 300+t*
Rwanda ca. 1000 t**Bur 50 t, Uga 100t***
CassiteriteDRC 24000 t*
Rwa ca. 4000t**Bur 20t, Uga 1200 t***
WolframiteDRC 1100 t*
Rwanda 500 - 3000 t**Uganda 800t***
GoldDRC ??, Rwa ??Uganda 930 kg***
AFPSampling
Central laboratory
Extension of CTC to additional countries
ICGLR+ EU / UN / WBIndustry (ITRI)
*Export numbers 2007 fromGarrett & Mitchell 2009**Export ordinaire (OGMR, BGR)***Production 2008Sasirwe & Turyahikayo 2009
Documentation
Standards
Raw materials from ASM
Checking instrument for CTC Standard 1
Use for “Whistle blowing”
Sudan
DRC
CAR
Tanzania
KenyaUganda
RwandaBurundi
SambiaAngola
Ethiopia
Egypt
NamibiaBotswana
ZimbabweMalawi
Mozambique
Congo
Projects of the BGR in theGreat Lakes region (ICGLR)
Analytical fingerprint (AFP) for “coltan“ (2006 - 2009)
“Certified Trading Chains“ (CTC) in Rwanda (2007-2010)
Enforcing controls in the raw material sector,DR Congo (2009-2012)
(Semi-) industrial producer
++ + +
+ +++
+
+Kougarok
Fir
Thor Lake
Motzfeldt
Coldwell
McAllisterAbu Dabbab
Ghurayyah
Kenticha
Marropino
Pitinga
Mibra
OrlovkaEtykinskoye
VishnjakovskojeLovozero
Rosendal
Yichun
Nanping+ ++
+
Greenbushes
Wodgina
+
801Forcarey
Blackstairs
Ma Ar Kan
Tanco
Area with artisanal production Exploration projects (selection)
+
+Morrua
ThailandMalaysia
500 t/afrom tin slags
Buyers/Powder makersH.C.Starck (GER, USA, Thailand)Cabot (USA, Japan)Ningxia, Jiujiang (China)AS Silmet (Estland)Mitsui (Japan)NAC Kazatomprom (Kazakhstan)Solikamsk (GUS)
Capacitor manufacturersAVX, Hitachi, Kemet, Sanyo,..
Electronic industry end users(OEMs, original equipment manufacturer)
Nokia, Samsung, Dell, Sony,…
Recyclers
Mineral producersTalison (Aus)Parapanema (Braz)Metallurg (Braz)Cabot (Can)Noventa (Moz)EMSDC (Eth)
Mineral dealersA&MRittenhouseTraxysKivu Metals
Artisanal producers
Tantalum production 2008: ca. 2000 t Ta2O5
African Tantalum Provinces
Pan-AfricanKibaranEburneanArchean
0.51.02.0
> 2.5
Ethiopia1) 530 Ma2) Mn-columbite/Mn-tantalite3) no tapiolite, cassiterite4) no bismutotantalite5) no or neg. Eu anomaly
Mozambique1) 440-480 Ma2) Mn-tantalite, microlite3) no tapiolite, cassiterite4) Bismutotantalite5) strong negative Eu anomaly6) anomalous Bi, Th, U
CAR-DRC Kraton (DRC)1) >1900-2500 Ma2) Fe-columbite/ Fe-tantalite3) Tapiolite, rare cassiterite4) no bismutotantalite5) negative Eu anomaly
Kibaran (DRC, Rwa)1) 930-1000 Ma2) Fe-columbite/ Mn-tantalite3) Tapiolite, cassiterite4) no bismutotantalite5) no Eu anomaly
South-Namibia (TV)1) 980 Ma2) Mn-tantalite3) no tapiolite, cassiterite4) no bismutotantalite5) negative Eu anomaly