Metamorphism and ultra-metamorphism, experimental petrology.
High pressure-temperature experimental studies of mineral equilibria (and partial melting) with application to the deep crust.
Petrological studies of regional metamorphism, especially in the deep continental crust (Ellis and students have worked in Antarctica, Central Australia, Broken Hill district, Sri Lanka, Norway, China). Emphasis has been on mineral equilibria and inferred tectonic settings of metamorphism.
The timing of zircon growth and resorption during regional metamorphism, in particular the trace element budget in common silicates and oxides and the effect this plays in zircon resorption/growth.
Geochemical studies of felsic igneous rocks produced under a variety of melting conditions (from water saturated migmatites) up to vapor-absent, pigeonite-bearing high-T "charnockitic" melts and their extrusive equivalents.
Ultra-high pressure blueschist-eclogites from western China.
