Continents in the Mantle Transition Zone? Sediment Recycling and the Geochemical Fertilization of the Deep Mantle. Because of its intrinsic compositional buoyancy, continental crust has traditionally been considered to be unsubductable in the denser underlying mantle. Yet some ocean island basalts carry a geochemical signature of recycled continental material in their plume source in the deep mantle. This project will reconcile this paradox through high-pressure experiments that will simulate su ....Continents in the Mantle Transition Zone? Sediment Recycling and the Geochemical Fertilization of the Deep Mantle. Because of its intrinsic compositional buoyancy, continental crust has traditionally been considered to be unsubductable in the denser underlying mantle. Yet some ocean island basalts carry a geochemical signature of recycled continental material in their plume source in the deep mantle. This project will reconcile this paradox through high-pressure experiments that will simulate subduction of continental sediments into the deep mantle. These experiments will provide the first empirical constraints on the role of sediment-derived fluids in mantle metasomatism and the origin of economically-rich potassic magmas, and the nature of the ultrarefractory continental component that ultimately reaches the plume source for ocean-island basalts.Read moreRead less
The Earth's Deep Carbon Cycle. The climate change debate has focused scientific attention on Earth’s exogene carbon-cycle. However, Earth has another, much deeper carbon-cycle which is poorly understood. In addition to exerting a profound influence on atmospheric greenhouse gas concentrations over time scales from thousands to billions of years, it is critically important in many processes in the Earth’s deep mantle. The major means by which the deep carbon-cycle is replenished is via subduction ....The Earth's Deep Carbon Cycle. The climate change debate has focused scientific attention on Earth’s exogene carbon-cycle. However, Earth has another, much deeper carbon-cycle which is poorly understood. In addition to exerting a profound influence on atmospheric greenhouse gas concentrations over time scales from thousands to billions of years, it is critically important in many processes in the Earth’s deep mantle. The major means by which the deep carbon-cycle is replenished is via subduction of carbonate-bearing oceanic crust. The project proposes a high-pressure experimental and field-based program to understand the fate of this carbonate during its journey from the exosphere, through subduction zones and into the deep mantle.Read moreRead less