Mantle metasomatism is an important mechanism by which trace elements are transported from one mantle region to another and likely involves agents ranging from silicate or carbonate melts to solute-rich hydrous fluids. It is not clear which agents are responsible for so-called cryptic metasomatism, for which otherwise difficult-to-explain trace element or isotopic features are the only evidence. Recent experimental work has identified a likely agent of cryptic metasomatism: highly silicic, aluminous, alkaline liquids with compositions like those of so-called extreme-composition glasses found in many mantle xenoliths worldwide. These results lead to the inference that such glasses represent liquids that were generated by partial melting of a pre-enriched mantle protolith, and could in fact migrate through the upper mantle and transport elements. To extend this work to an examination of the possible trace-element signatures they can impart, this study will determine partitioning behavior between these liquids and mantle minerals. It will provide more accurate information on how these liquids might transport trace elements, elucidate the role of liquid composition on trace element partitioning behavior, and refine parameterizations of partitioning data that can yield predictive relationships for trace element partitioning as functions of pressure, temperature, and mineral and melt compositions.
