| We have assembled a multi-national team with access to the most advanced analytical equipment to study diamond genesis. A collection of well characterised diamonds from two Archaean cratons will be studied in detail to constrain better the processes responsible for diamond formation and the factors that affect their growth. A particular goal will be to determine the likely time scale of diamond growth, a parameter that is still surprisingly poorly constrained. We will examine factors governing diamond nucleation and study the subsequent growth history of diamond crystals. Our approach will be to build on detailed crystallographic studies utilising FTIR and cathodoluminescence to determine the growth history of individual diamonds prior to performing state-of-the-art in situ C-N isotope analysis on well characterised diamond plates. In addition, mineral inclusions will be subjected to detailed major (microprobe) and trace element (SIMS, PIXE, LA-ICP-MS - depending on size) analysis and sulfide inclusions will be dated using ultra-low blank Os and Pb isotope techniques. This integrated and innovative approach is designed to provide unparalleled information about the temporal evolution of fluid sources in the mantle. Comparison of this information with ongoing complementary studies of peridotite and eclogite xenoliths will also contribute to a far better understanding of the extent to which the sub-continental lithospheric mantle (SCLM) has been modified since initial formation in the Mid Archaean. The importance of this combined approach is that the SCLM largely dictates the isostatic and rheological response of continents during large-scale deformation events and consequently controls near-surface tectonics and the topography of the Earth's continental crust. Understanding how the processes that modify the SCLM have varied with time is critical if we are to successfully model the past tectonic events that have built our planet. |
