Measuring Trace Element Partition Coefficients Between Minerals and Basaltic Melts

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LundstromEAR-0000924Igneous petrology has experienced an exponential increase in the number of observational geochemical data over the past 20 years, leading to fundamental changes in our view of the physics of magmatic processes. Interpreting these data requires a better understanding of how trace elements distribute themselves between mantle minerals and melts. This project will provide relevant trace element partitioning data for a wide range of elements (rare earth elements, high field strength elements, and large ion lithophile elements) between clinopyroxene or plagioclase and potential mantle melts. Specifically it will provide constraint on the partition coefficients between clinopyroxene and melt relevant to the upper portions of a mantle-melting column by focussing on depleted clinopyroxene compositions in equilibrium with depleted basaltic melts. Particular attention will be paid to the effects of variations in both melt and crystal composition. In addition, the project will constrain the partition coefficients for a variety of trace elements between plagioclase and melt. Melts examined in this case will range from basaltic to andesitic. The experiments will be performed in either a piston cylinder apparatus or a 1-atmosphere furnace using both natural and synthetic starting materials. Experiments will be analyzed by electron and ion microprobe. Results will be parameterized with the goal of predicting trace element partitioning behavior as a function of depth in mantle melting column. These experiments will provide needed partition coefficient data for interpreting trace element and uranium-series disequilibria data from a variety of tectonic regimes on the planet. The resulting data will be incorporated into geochemical models of two-phase flow in order to gain further constraint on the physics of magmatic processes in the mantle.