The research will help better understand this process caused by collision of the Earth’s tectonic plates. Gasching will use molybdenum and thallium isotopes as tracers to follow the chemical transfer.
“This is basic research, so its contribution to society is more in terms of expanding our scientific understanding of how the Earth works,” says Gaschnig. “In this project, we’re aiming to fill the central gap in the understanding of the molybdenum isotope cycle. This may ultimately give us a better grasp of how molybdenum ore deposits form.”
Molybdenum is an important chemical element that is used commercially to make ultra-high-strength steel and heat- and corrosion-resistant materials used in the chemical and nuclear power industry. Molybdenum is also used to make missile and aircraft engine parts, electric heater filaments, drill bits, saw blades, lubricant additives and other products. It is also used as a catalyst in refining petroleum.
Gaschnig says Earth is unique among known rocky planets in our solar system in that its solid outer layer, or crust, is broken up into tectonic plates that move around, albeit very slowly, “at about the speed fingernails grow.”
Along the subduction zone
– the boundary where Earth’s tectonic plates converge – the ocean crust gets pushed under the continental crust and into the earth’s deep interior, or mantle. Gaschnig’s research aims to better understand the chemical interaction that occurs between the sinking ocean crust and overlying mantle during subduction.
“This research is fundamentally about figuring out how materials are transferred from the Earth’s surface to the planet’s deep interior, and back to the surface again,” notes Gaschnig.
According to Gaschnig, the process allows materials that chemically interacted with air and water at the Earth’s surface to contaminate its interior. “At the same time, the sinking crust releases fluids that trigger melting of the mantle, which leads to the formation of volcanic mountain chains like the Cascade Range in the Pacific Northwest. So as a result, some of that subducted surface material ends up making a geologically quick return to the surface via these volcanoes,” he explains.
“The exact nature of the processes that occur in the sinking crust and how they drive the formation of volcanoes on the surface remain incompletely understood, and there are a lot of competing models,” he says.
To find out, Gaschnig will investigate places where these subducted rocks have actually been re-routed back to the Earth’s surface intact. “For this NSF project, my students and I will be looking at rocks from the Western Alps in Europe and Catalina Island off the coast of California.”