Dunite channels as viable pathways for mare basalt transport in the deep lunar mantle

Lunar picritic glasses are multisaturated with olivine and orthopyroxene at pressures up to 2.45 GPa. This corresponds to a depth of approximately 490 km in the lunar mantle and represents a minimum estimate of the depth of melt generation. Models that propose a mechanism to move these melts through the mantle and crust generally involve the creation of a network of fractures through which melt can rise very rapidly, minimizing its interaction with shallower mantle. We carried out an experimental study of harzburgite dissolution in a synthetic high Ti red glass. Our results show that during ascent of olivine saturated melts, dissolution of wallrock orthopyroxene and precipitation of olivine leads to the formation of high porosity, high permeability dunite channels that efficiently shield subsequent melts from reaction with the mantle. These dunite channels are similar to dunite dikes observed in ophiolite sequences which are believed to be channels for mid-ocean ridge basalts. Models for lunar melt migration that require brittle fracturing extending to the depths of multisaturation need not be invoked.