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Terrane Assembly and Lithospheric Modification Processes in Antarctica Approached Using Magnetotelluric Geophysics
With its land area 97% covered by thick ice, understanding tectonic processes below the Antarctic continent could benefit from geophysical investigation. Magnetotelluric (MT) imaging for electrical resistivity structure of the crust and upper mantle are in relative infancy compared to seismic velocity coverage. However, the large data frequency bandwidth of MT data carries the potential of resolving structure from a few 100s m depth through the upper mantle. Resistivity appears also to be uniquely affected by volatile presence through both solid state and boundary phase mechanisms, with attendant implications for element transport, thermal regime and rheology. Instrumentation enhancements are required to accommodate the high contact resistance of the ice, and data processing must be careful for MT responses to meet their plane-wave assumption. Two field examples will be discussed. One will be a profile across the transition from rifted West Antarctica to cratonic East Antarctica showing thermal and hydration states of the upper mantle, uplift support of the rift shoulder, and possible Proterozoic fossil terrane boundaries. The second will be comprehensive 3D coverage of the Mount Erebus/Ross Island, active CO2-dominated, ultra-alkalic volcano system showing crustal scale controls on magmatic plumbing and a strong contrast with H2O-dominated arc systems. Opportunities for the future include clarifying assembly of Precambrian East Antarctic terranes and in revealing variations in heat flow to the base of ice sheets as pertains to their stability.

Jan 21, 2021 02:00 PM in Eastern Time (US and Canada)

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