A Towed Electromagnetic Survey Across the Kane Megamullion: Mapping the Uppermost Gabbro/Serpentinite Contact

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Intellectual Merit: Oceanic core complexes (OCC) are widespread features along the mid-Atlantic Ridge and other slow and ultra-slow spreading ridges. They are often found in inside corners of ridge discontinuities, and recently have been observed to occur in clusters over large areas of the seafloor. Sampling of these structures has shown that they are low-angle detachment faults exposed at the seafloor that unroof and expose sections of lower crust and mantle. These faults accommodate large amounts of deformation through effective strain accumulation over periods of time, sometime in excess of 1 Myrs. The uplift and exposure of mantle peridotite is inherent to the uplift process. The presence of shallow peridotite promotes serpentinization across the features that, in at least one instance, results in moderate temperature hydrothermal venting fueled by exothermic reactions associated with the serpentinization. Discrimination of serpentinite from gabbro is difficult on the basis of seismic velocities alone. We suggest electrical conductivity as an alternative approach to identifying serpentinite within OCCs. This project is a ?proof-of-concept? pilot experiment, towing a seafloor EM system across the Cain and Abel domes within the OCC south of the Kane transform fault on the Mid-Atlantic Ridge. This will test our ability to discriminate, on the basis of electrical conductivity: a) the uppermost (~0-30m) contact geometry (laterally) between serpentinite and gabbro across the dome of the mound; and b) the variations in the nature and geometry of the fault core that accommodates most of the strain during plate separation. This experiment will be the first of its kind.Broader Impacts: This project marks the start of an international collaboration between the P.I. and scientists at IPGP in Paris. We anticipate a number of joint activities that will include seeking funds for the PI to spend time in Paris, and for Paris colleagues to visit WHOI. The data set collected in this pilot study will be appropriate for a small general examination project or as a project for a summer student fellow. WHOI runs a summer student program which annually brings around 20 students for 12 weeks and exposes them to their own research project and to a wide range of educational experiences. Many of these students go on to graduate school. The institution also supports and runs a minority trainee program which seeks to expose students from underrepresented backgrounds to ocean science. If appropriate candidates apply, then a summer student could come from this pool.