Research

 

Genesis, evolution and emplacement of kimberlite and related melts

Kimberlites, together with orangeites (also known as Group II kimberlites) and olivine lamproites, are the major host-rocks of terrestrial diamonds. They are small-volume volcanic rocks that derive from deep in the Earth’s mantle. These rocks can provide a wealth of information about the composition of Earth’s interior, and the melting processes which have shaped the evolution of our planet. However, significant uncertainties remain about the composition, origin, evolution and emplacement of kimberlites and related magmas. To address these questions, we study kimberlite and related rocks from worldwide localities employing detailed textural and petrographic examination combined with geochemical measurements of major and trace element contents, radiogenic and stable isotope compositions of minerals, and age dating.

 

 

Diamond formation and preservation

It is easy to forget that diamonds are a form of crystalline carbon with minor impurities, derived from metasomatism of deep mantle domains. But how and when do diamonds form? Which fluids produce diamonds and which fluids destroy them? These are fundamental questions that are being addressed by the KiDs group, using an innovative approach that study diamonds as a part of the kimberlite system. We are also working with our industry partners to develop new techniques to improve evaluation of diamond resources and diamond exploration strategies.

 

 

Mantle metasomatism

Metasomatism is the process of enrichment of rocks by fluids. The compositions of these fluids can show extraordinary variation. By studying metasomatic processes in the mantle we can understand the transfer of chemical components, including base and precious metals, in the deep Earth. This may also aid our understanding of the formation of enriched domains that represent preferential melting sites. We investigate mantle metasomatism by examining mantle rocks enriched in minerals such as phlogopite, amphibole, clinopyroxene, ilmenite and zircon, which are transported to surface by kimberlites, orangeites and alkali-basalt magmas from southern Africa and Australia. Current projects focus on understanding the composition and source of mantle fluids by coupling textural, petrographic and fluid inclusion studies with determinations of the radiogenic and stable isotope compositions of mantle minerals.