Effects of Composition and Temperature on the Phase Boundaries in the Mantle Transition Zone — Implications for the Archean Mantle and the Mantle Plumes
IPGP - Îlot Cuvier
Arizona State University
The mantle transition zone at 400-700 km depths plays important roles in the chemical evolution of the Earth. Seismic studies have discovered complex structures in the region. Whereas some of the structures have been attributed to lateral variations in temperature, many seismic observations cannot be explained solely by thermal origins. In addition, high temperature alters the phase relations in the mantle transition zone, resulting in different structures and dynamics for the Archean mantle and the mantle plumes. In this talk, I will report new data on the mantle transition zone phase boundaries in different compositions at a wide range of temperature. I will discuss (1) compositional effects on the phase boundaries, and (2) changes in phase relations at high temperatures. I will also discuss implications of the results for the structure and dynamics of the Archean mantle and the present-day mantle plumes.