Piston-cylinder apparatus

The Research Tools and Instruments Grant is requested to purchase a piston - cylinder apparatus for high pressure (P) - temperature (T) experiments that simulate conditions during the ascent of deep mantle magma from its source in the upper mantle (> 100 km depth). Kimberlite magmas bring to the surface diamonds and other mantle minerals such as garnets, ilmenites, chromites. All these minerals exhibit variety of surface features attributed to a reaction with the kimberlite magma. My previous experimental results showed that the conditions of kimberlite magma (T, P, oxidation state) determine the degree of diamond preservation, whereas the character of surface dissolution on diamonds depend on H2O/CO2 ratio of the magmatic fluid. Therefore, surface features of diamonds can be used to derive the fluid composition of the host kimberlite. The proposed research will develop a new method for investigating fluid system of diamond-bearing magmas and conditions during their emplacement. Further calibration requires experiments over larger T - P range and taking into consideration other volatiles (e.g. chlorine). When applied to natural diamond parcels this method will put new constraints on origin and evolution of kimberlites. Dissolution forms on kimberlite-hosted garnets, chromites and ilmenites can provide another way to constrain composition of kimberlitic fluid, that can be used for predicting the quality of diamonds in a kimberlite pipe. The experiments will study reaction between these minerals and kimberlite magma to determine what produces the different dissolution features: fluid composition, magma conditions, or composition of kimberlite melt. Complex chemical composition of these minerals and their relative abundance, compared to diamonds, allows investigating evolution of kimberlitic fluid with depth and time. The project will develop tools for studying fluid system of mantle-derived magmas and for predicting diamond quality in kimberlite pipes.