Magnetotelluric image of a hyper-extended and serpentinized rift system

Magnetotelluric (MT) data can image the Earth's electrical resistivity down to mantle but are rarely used for investigation of offshore rifted margins. In such settings, lower crust and upper altered by distinct tectono-thermal processes often display similar seismic velocities densities. By integrating models from MT data, we aim at resolving ambiguity. Here, 3D inversion long period, marine (1 – 3000 s) is performed on 104 receivers located along two, ∼300 km transects in SW Barents Sea. The power assessed with synthetic tests an archetypal rift system where ample crustal thickness variation occurs. results highlight that our sense transition necking hyper-extended domain (<10 km) not recovered inversion. Bjørnøya Basin northernmost member a Cretaceous basin chain NE Atlantic combine interpretation assign properties two depth intervals: (1) 0.1-1 Ωm within Lower shales buried 10-15 (2) 1-10 uppermost mantle. Based fluid-rock model, emphasize seawater as sole pore fluid phase conductive enough explain high bulk conductivities both intervals. A 25% serpentinization rocks account fivefold rise salinity residual compatible resistivity, density, Basin. Such high-salinity ascend mix spaces sediments, supporting model saline circulation basins. conclusion, disambiguate deep structures margin detecting fluids partial serpentinization, intermixing overlying sediments.