Analysis of diamonds and indicator minerals for diamond exploration by laser ablation–inductively coupled plasma mass spectrometry

Abstract

A method has been developed, using laser ablation–inductively coupled plasma mass spectrometry (LA–ICP-MS), for the semiquantitative determination of 43 elements in diamonds, chromites and garnets. Samples of diamonds from five countries have been analysed and the interrelationship between the trace elements gives distinctive patterns for each source. The data indicate that this technique could form the basis of a provenance identification protocol for diamonds. This would produce an analytical technique to assist police forces in tracing the origin of stolen material. LA–ICP-MS can also be used to establish the trace element distribution in indicator minerals for diamond exploration, such as garnets and chromites. Of particular significance in this data set in the comparison of the relative distributions of the rare earth elements, tantalum and hafnium, which indicates a consistent inter-element relationship for garnets associated with diamondiferous kimberlites. This relationship is considerably different from that found in garnets obtained from non-diamondiferous and other sources. Application of the principle of trace element partitioning pattern recognition to chromites has indicated the potential of the technique to identify also a kimberlitic or non-kimberlitic provenance for this mineral. The data presented here are the result of preliminary investigations. A more detailed study is currently being undertaken and will be the subject of future papers.