This research carries out a set of detailed experiments on high temperature plagioclase crystals at crustal pressures and water contents to allow calibration of numerical models of magmatic processes. The importance of this work is that the zoning patterns of feldspar crystals are similar to tree rings in that the zones are often concentric and record the chemical changes that have occurred over time during the growth of the mineral, in this case recording changes in the composition, temperature, and pressure of magmas in which they grew. As such, these minerals can reveal information on the amount of melting in the mantle, the crystallization of a magma, magma residence times, the interaction of magma bodies with the lower crust, and the amount of mass and heat transfer from the mantle to the crust. In short, how the Earth's heat engine works. At present, it is not clear how elements distribute themselves as a function of temperature, pressure, and composition, including H2O in these minerals. The funded research is designed to examine the zoning of Li, Ba, Sr, Pb, Zr and rare earth elements in anorthite plagioclase at pressures to 0.7 GPa in the presence of 0 to 1.5 weight percent H2O. Experiments have been designed with the specific goal of understanding magmatic processes that create the ocean crust, in particular, that associated with slow and intermediate spreading centers and fracture zones. Data will be incorporated into thermodynamic databases for modeling melt composition and evolution. Broader impacts of the work include graduate student training and building essential datasets that make up the infrastructure for science.
