Stability of Melt-rich channels in Earth’s Mantle: High Pressure and Temperature Experiments on Olivine, Chromite and MORB

April 29th, 2008

Melt transport, the movement of molten rock through the Earth’s relatively solid outer shell, is important in many geological processes. Volcanism at subduction zones and hot spots and the formation of oceanic crust at mid-ocean ridges all involve melt transport. To increase our understanding of how melt moves from depth to Earth’s surface, we conducted experiments at high temperature and pressure on fabricated rock samples of modeled mantle rock compositions.
We deformed these rock samples, containing olivine and chromite and 4% mid-ocean ridge basalt, at a constant twist rate at experimental conditions of 1473 K and 300 MPa. These conditions are comparable to the temperature, pressure and stress conditions experienced by rocks within Earth’s mantle and at which melt segregates or separates into layers. In our experiments, the samples were then exposed to a 4-hour static anneal at 1473 K and 150-200 MPa to cause the melt from the melt-rich layers to dissipate and redistribute homogeneously. Our observations demonstrate that surface tension is an important factor in melt redistribution when a stress is no longer present. These small scale experimental results, obtained on cylindrical samples a centimeter in diameter, can be scaled to the sizes appropriate for Earth processes, helping to expand our knowledge of how the Earth removes heat from within by transporting melt in channels from the mantle to the surface. NASA sponsors this research because a solid understanding of Earth processes helps us understand similar processes on other planetary bodies.

Kristyn Rodzinyak, ’09 Colorado Springs, CO
Majors: Geology, Chemistry
Dan King
University of Minnesota
Mark Zimmerman
University of Minnesota
David Kohlstedt
University of Minnesota

Sponsor: Emily Walsh

Comments are closed.