ProjectB1
From !khure
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# the trace element contents of diamond (LA-ICPMS, SIMS) | # the trace element contents of diamond (LA-ICPMS, SIMS) | ||
# the magnetic properties (cryomagnetic characterization) | # the magnetic properties (cryomagnetic characterization) | ||
| - | Because diamond characteristics (size, shape, color, plastic deformation, isotope characteristics) are highly variable within a single diamond mine, distinguishing a conflict diamond be distinguished from a legitimate diamond is unlikely. | + | Because diamond characteristics (size, shape, color, plastic deformation, isotope characteristics) are highly variable within a single diamond mine, distinguishing a conflict diamond be distinguished from a legitimate diamond is unlikely.</p> |
| + | <p>Of these other methods, 2-6 characterise chemical signatures, whilst the last (7) reflects a physical property of diamonds that has hitherto not been tested.</p> | ||
| + | <h3>Using established techniques</h3> | ||
| + | <p>Because each mine show some of the parameters 1 to 6 listed above to vary from one mine to the other (a single parameter is not pertinent enough), we can potentially provide a way to chemically identify conflict diamonds using a complete chemical diamond characterisation methodology.</p> | ||
| + | <p>As a first step, we propose to combine parameters 1 to 3 since these are relatively rapid and non-destructive techniques. These techniques will be applied to specimens from a variety of sources with a view of building up a global database of the above characteristics. For this purpose, we have already obtained a pilot sample of diamonds from the Mbuji Mayi in the DRC.</p> | ||
| + | <p>The study of carbon and nitrogen stable isotopes, nitrogen contents (Parameter 4) can be undertaken using (compared to SIMS measurements) well established, rather rapid, accurrate, yet destructive techniques. If successful in tracing the origin of diamonds, this destructive technique would not be an appropriate one anymore because then the sample must be preserved, but SIMS will be. Thus in the first instance, the method will allow to fastly expand the database to conflict and yet unstudied legitimate diamond mines.</p> | ||
| + | <p>The strengh of using parameters 1 to 4 is that these can already use the significant amount of data obtained during the last 30 yeras on legitimate worldwide diamond productions.</p> | ||
| + | <h3>Developing new techniques</h3> | ||
| + | <p>There are potentially several new non-destructive ways to characterize both the physical and chemical properties of diamonds that are briefly summerized below.</p> | ||
| + | <h4>Chemical fingerprinting using trace elements</h4> | ||
| + | <p>Ongoing with this work will be to explore new routes to reliable non-destructive chemical fingerprinting of diamonds of parameters 6. We believe this can be done as briefly described below:</p> | ||
| + | <p>Trace element geochemistry of diamond is relatively well known, and unfortunately to date the bulk or trace element compositions of diamonds are of little value to reveal their origin (Griffith et al., 2006). Moreover the geochemical methods are largely destructive, thus obliterating the diamond sample. Yet the geochemical signatures of individual diamonds, both in the form of trace element and isotopic compositions, have the potential for geographically localizing the origin of a crystal of unknown provenance. Through the use of modern micro analytical techniques it is possible to conduct such measurements in a nearly non-destructive fashion. For this strategy to be applied to the trade in conflict diamonds there are three geochemical questions which must be addressed: | ||
| + | # Are diamonds, in general, homogeneous in their compositions such that a single measurement from any surface is representative of an entire crystal? | ||
| + | # Do diamonds from a common source have one or more geochemical traits which are common to all crystals from that geographic unit (e.g., single diamond pipe or single cratonic region)? | ||
| + | # Do diamonds of different geographic origins differ significantly in one or more such characteristics? | ||
| + | If the answer to each of these three issues is “yes”, then the potential exists to constrain or even localize the source of individual crystals. The first step in this research initiative must therefore be to address all three of these issues. | ||
Revision as of 12:22, 6 July 2009
Contents |
Project B1: African Diamond Genesis and Craton Evolution: Exploring new ways to characterise conflict diamonds
French pi: P. Cartigny (with S. Gilder and C. Aubaud)
South African pi: M. de Wit (with S. Richardson and D. Bell)
Project Participants
- France: Pierre Cartigny, IPG-Paris
- South Africa: Maarten de Wit, Steve Richardson, Cape Town
- Germany: Stuart Gilder, Munich; Michael Wiedenbeck, Potsdam
- Exploration Industry: Mike de Wit, Hielke Jelsma, Kinshasa and Johannesburg.
Introduction
Diamonds known as conflict diamonds, otherwise known as blood diamonds, originate from the war zones of Africa, and specifically from areas controlled by forces or factions opposed to legitimate and internationally recognized governments, and are used to fund military action in opposition to those governments, or in contravention of the decisions of the United Nations Security Council. On December 1, 2000 the UN General Assembly unanimously adopted a resolution defining the role of conflict diamonds with the intent of cutting-off the sources of funding for rebel forces and to help shorten the wars and prevent their recurrence through breaking the link between the illicit transaction of rough diamonds and armed conflict (from: David Cowley, 2007. What Are Conflict Diamonds?).
In May 2000, the diamond producing/trading industry took the first steps to develop a plan that could halt the trade of conflict diamond by establishing a way that diamonds could be certified, and created the Kimberley Process Certification Scheme (KPCS). Yet, governments want the KPCS to be monitored with more transparency and certainty to identify the place of origination of the diamonds. For example, Canada is a major diamond producer, and being member of the Kimberley Process Certification Scheme and (among others) is particularly concerned in regulating the legal diamond industry. Europe is the strongest partner of most African countries because they are a major donor or aiding development in third world countries and is thus concerned in solving conflicts in this part of the world. The fact that the European Commission assumes duties as Chair of the Kimberley Process for 2007 is a further reason why Europe is particularly concerned in monitoring the Kimberley Process Certification Scheme. The benefits to countries that put an end to trading in conflict diamonds are immense and it could mean better economic development and prosperity throughout Africa. Yet, resourceful and unscrupulous groups still manage to elude the legal barriers and still find ways of infiltrating the diamond centers of the world.
Although this list is not exhaustive and will likely change trough time, the main countries concerned so far by this resolution are: Angola, Sierra Leone, Liberia, Ivory Coast, Democratic Republic of Congo, Republic of Congo, Central African Republic. In terms of geology, these diamonds originate largely, but not exclusively, from two regions, namely the West and Central Africa Shields.
The question asked of scientists is either How can a conflict diamond be distinguished from a legitimate diamond; or [and this is not the same question] how can conflict diamonds be distinguished from legitimate diamonds?
Nobody can answer any of these two questions yet, as no one ever studied conflict diamonds scientifically in earnest; and in particular no one has yet mastered a non- destructive technique that has the potential to be fast enough to be enable examining bulk samples. Answering these questions require representative suites of conflict diamonds to be made available to scientists. It also require every legitimate mine to have its diamond production well characterised (which is not always the case).
Method(s)
Given that some conflict and legitimate diamonds are presently mined within a same region, the method to identify conflict diamonds must be sensitive on the local scale (i.e. the diamond mine) and not to a regional scale only (from one craton or shield to the other).
A large amount of data have been obtained on legitimate diamonds since the last 30 years and one can use these to discuss to potentially recognise diamonds from one legitimate diamond mine from another legitimate diamond mine.
Parameters that can be used to trace the origin of diamonds are:
- the physical characteristics (color, shape, resorption, surface features)
- the types (eclogitic/peridotitic ratios), nature of the inclusions (silicate, sulfide)
- the speciation of nitrogen and its aggregation state (FTIR)
- the stable isotope (C, N) compositions (mass spectrometry or SIMS)
- the radiogenic isotope compositions of diamond inclusions (TIMS)
- the trace element contents of diamond (LA-ICPMS, SIMS)
- the magnetic properties (cryomagnetic characterization)
Of these other methods, 2-6 characterise chemical signatures, whilst the last (7) reflects a physical property of diamonds that has hitherto not been tested.
Using established techniques
Because each mine show some of the parameters 1 to 6 listed above to vary from one mine to the other (a single parameter is not pertinent enough), we can potentially provide a way to chemically identify conflict diamonds using a complete chemical diamond characterisation methodology.
As a first step, we propose to combine parameters 1 to 3 since these are relatively rapid and non-destructive techniques. These techniques will be applied to specimens from a variety of sources with a view of building up a global database of the above characteristics. For this purpose, we have already obtained a pilot sample of diamonds from the Mbuji Mayi in the DRC.
The study of carbon and nitrogen stable isotopes, nitrogen contents (Parameter 4) can be undertaken using (compared to SIMS measurements) well established, rather rapid, accurrate, yet destructive techniques. If successful in tracing the origin of diamonds, this destructive technique would not be an appropriate one anymore because then the sample must be preserved, but SIMS will be. Thus in the first instance, the method will allow to fastly expand the database to conflict and yet unstudied legitimate diamond mines.
The strengh of using parameters 1 to 4 is that these can already use the significant amount of data obtained during the last 30 yeras on legitimate worldwide diamond productions.
Developing new techniques
There are potentially several new non-destructive ways to characterize both the physical and chemical properties of diamonds that are briefly summerized below.
Chemical fingerprinting using trace elements
Ongoing with this work will be to explore new routes to reliable non-destructive chemical fingerprinting of diamonds of parameters 6. We believe this can be done as briefly described below:
Trace element geochemistry of diamond is relatively well known, and unfortunately to date the bulk or trace element compositions of diamonds are of little value to reveal their origin (Griffith et al., 2006). Moreover the geochemical methods are largely destructive, thus obliterating the diamond sample. Yet the geochemical signatures of individual diamonds, both in the form of trace element and isotopic compositions, have the potential for geographically localizing the origin of a crystal of unknown provenance. Through the use of modern micro analytical techniques it is possible to conduct such measurements in a nearly non-destructive fashion. For this strategy to be applied to the trade in conflict diamonds there are three geochemical questions which must be addressed:
- Are diamonds, in general, homogeneous in their compositions such that a single measurement from any surface is representative of an entire crystal?
- Do diamonds from a common source have one or more geochemical traits which are common to all crystals from that geographic unit (e.g., single diamond pipe or single cratonic region)?
- Do diamonds of different geographic origins differ significantly in one or more such characteristics?
