This research is a highly coordinated, multi-lab, collaborative effort to measure the density and compressibility of magmas that form during melting in the Earth's interior. The measurements will greatly advance our ability to predict the conditions under which magmas will rise buoyantly to the Earth's surface and erupt as lavas or form volcanoes. The measurements will also reveal the conditions and depths where magmas are too dense to rise to the surface, remaining either trapped by neutral buoyancy, or sinking further into our planet's deep interior. The experimental data will also provide new insight into the way in which the Earth was differentiated into crust, mantle, and core during its primordial formation stage. The collaborative effort combines experimental techniques that span the entire range of pressure and temperature conditions that exist for melting and magma production in the Earth. The highest pressures, simulating the deepest regions of Earth's mantle, will be done under dynamic compression at the Caltech Shockwave Laboratory, the intermediate pressures will be carried out under static compression in large presses at the University of New Mexico's High Pressure Laboratory, and the near-surface magmatic conditions will be studied in high temperature furnaces with ultrasonic techniques at the University of Michigan's Experimental Petrology Laboratory.
The new data will lead to the development of an empirically-based equation of state and a model for multicomponent silicate melts. This model should allow precise characterization of the locations of crystal/melt density crossovers in the upper mantle, transition zone, lower mantle, and D" layer. This equation of state will be used in models of differentiation of a whole-mantle magma ocean or in defining the chemistry and dynamics of possible silicate melting at the modern core-mantle boundary. The investigators expect that the data will also provide the essential basis for development of next-generation melt models that encompass explicit speciation and/or non-ideal mixing terms. The data gathered under this proposal will be a precious resource for all future studies of melt properties and igneous differentiation at high pressure. Never before have such a wide range of techniques been applied to a common set of samples; together the complementary data sets will significantly enhance our understanding of magma physics within our planet.
