EPIC-recovery

This project will carry out a joint seismic and electromagnetic investigation that is designed to specifically address critical questions associated with quantifying melt distribution in the oceanic mantle. The experiment spans ~500x500 km of the Cocos Plate, centered on a sharp boundary in bathymetry that corresponds to a fracture zone (FZ) in the Guatemala Basin. The FZ has a 200–400 m depth offset that is too large to be attributed to subsidence from the 1–2 million years difference in plate age. Because intraplate volcanism and mantle melts have only been documented south of the FZ and the step in bathymetry across the FZ does not correspond with a step in the free-air gravity anomaly, this suggests the FZ also marks a sharp boundary in both the northern extent of magmatism and of melts in the mantle. Yet insufficient geophysical and geochemical data are available to confirm this hypothesis. We will collect ocean-bottom seismic and magnetotelluric data to image the seismic velocity and electrical resistivity of the lithosphere and asthenosphere in order to (1) determine the spatial and depth extent of mantle melts and (2) characterize the geophysical signature of melt-bearing mantle. We will also collect underway data to fill in data gaps and to identify sites suitable for dredging selected seamounts on both sides of the FZ to (1) determine whether the seamounts north of the FZ were also erupted intraplate and (2) constrain the provenance of the seamounts.