Kimberlite Crystallization and Emplacement Through the Lens of Mantle-Derived Ilmenite and Chromite

Abstract

This thesis explores kimberlites through the lens of mantle-derived oxides, ilmenite and chromite. These minerals are entrained during the ascent and by interacting with the kimberlite magma, develop various reaction textures. In the first study of this thesis, analysis of ilmenite and chromite macrocrysts in Orapa kimberlites reveal that unique reaction textures develop in different kimberlite lithologies. The second study of the thesis investigates the controls of ilmenite dissolution through piston-cylinder experiments. These experiments successfully reproduced reaction textures observed in the natural samples. The final study explored oxide distribution and development of reaction textures in several kimberlite localities which exhibit varying morphologies and lithologies. The results reveal a distinct correlation between ilmenite and diamond grade. The thesis demonstrates that reaction textures on oxides provide a wealth of information that contributes to our understanding of these enigmatic rocks.