Episodic melt transport at mid-ocean ridges inferred from magnetotelluric sounding

Oceanic crust is generated at mid-ocean ridges by decompression melting of upwelling mantle at depths of between 50 and 120 km. Geodynamic and geochem ical models of upwelling, melt extraction, and melt emplacement into crusta l magma reservoirs present a variety of possible migration geometries, most of which assume steady-state or near steady-state processes. Here we prese nt results from marine magnetotelluric (MT) measurements, carried out as pa rt of the RAMESSES experiment on the slow spreading Reykjanes Ridge, which support a model of melt extraction and migration that is episodic, rather t han steady-state.