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

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

3

1

2 45

6

7

8

9

10

Important Tantalum Provinces in Africa

Burundi

Rwanda

Uganda

DRC

Kibaranca

. 930

- 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

0

20

40

60

80

100

0 20 40 60 80 100

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

0,01

0,1

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100

1000

10000

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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La Ce Pr Nd Sm Eu Gd Tb Dy Y Ho Er Tm Yb Lu

Sam

ple/CI

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1000

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100000

La Ce Pr Nd Sm Eu Gd Tb Dy Y Ho Er Tm Yb

Sample/CI

Nuweibi, Somalia

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1000

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100000

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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1000

10000

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

Bijyojo, Ruanda Pangi, Kongo

Mineralogy mode Grain sizes Grain shapes Intergrowths

Laser ablation – ICP – mass spectrometry

Laser

El. beam

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

Estimated U-Pb age from LA-ICP-MS data

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

Similar ages ( 930 – 990 Ma), but different mineralogical compositions

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

0.001

0.01

0.1

1

10

100

100 1000 10000 100000

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

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”

Tantalum

coltan

ThankYou !

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