Melt Migration – Peč Lab

Melting along spreading centers, subduction zones and hotspots is one of the fundamental manifestations of plate tectonics. Melt extraction affects much of the chemical exchange between mantle, crust and the atmosphere. Geochemical, geophysical and geological evidence suggests that, at some stage of melt extraction, melt must segregate into high permeability channels. These channels must be isolated enough to preserve chemical disequilibrium and permeable enough to allow fast melt extraction in order to preserve radiogenic disequilibrium. In nature, melt segregation is inferred to occur due to an interplay between reaction and deformation. Detailed knowledge of the physical and chemical processes leading to melt channelization, as well as their interactions, is hence critical for our understanding of Earth’s evolution and differentiation.

To study the physical and chemical processes occurring during melt channelization due to melt-rock reactions, we have developed a new experimental set-up which allows us to perform Darcy-type experiments at high pressures and temperatures.

This set-up allows us to flow a reactive melt through a partially molten rock at various rates. The ratio of the flow velocity to the reaction timescale can be therefore controlled and a rich behavior is observed. If the melt flow velocity is slow, a planar reaction layer formed of olivine and melt is observed, once the velocity reaches a critical threshold, finger-like melt-rich channels formed of olivine and melt form and cause a rapid increase in bulk permeability.