Channeling instability of upwelling melt in the mantle

Presents results of a theoretical study aimed at understanding melt extraction from the upper mantle. Specifically, this paper addresses mechanisms for focusing of porous flow of melt into conduits beneath mid-ocean ridges in order to explain the observation that most oceanic residual peridotites are not in equilibrium with mid-ocean ridge basalt. It is shown that flow in a chemically reactive porous media is unstable in the presence of a solubility gradient, such as induced by adiabatic ascent of melt underneath mid-ocean ridges. The initially homogeneous flow becomes focused in time to produce elongated high-porosity fingers that act as conduits for transport of fast flowing melt. This instability arises due to a positive feedback mechanism. -from Authors