Electromagnetic studies of crustal fluids and dynamics

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Fluids, such as water and partial melt, are widely distributed in the interior of the Earth. They are important because they are involved in many geological processes, such as the formation of mineral deposits and the transfer of heat in geothermal systems. In addition, fluids can change the strength of rocks and control how the Earth's tectonic plates will deform at plate boundaries. ***Mapping fluid distribution within the Earth requires the use of geophysical data measured at the surface to determine the properties of rocks at depth. Seismic imaging uses sound waves and is one of the most widely used techniques in oil and gas exploration. Electromagnetic exploration methods use low frequency radio waves to image the subsurface and are important tools in mineral and geothermal exploration. Magnetotellurics (MT) is an electromagnetic method that uses natural, low frequency, radio signals to determine the electrical resistivity from the surface to a depth of several hundred kilometers. In this proposal, research will be carried out that will improve the ability of MT to reliably image subsurface fluids, by combining multiple types of geophysical and geological data. ***These methods will be applied to a number of problems. In order of increasing depth, these are (1) geothermal exploration in Western Canada where the MT data will be used to locate resources for electric power production (2) studies in Chile of a very active magma body that shows signs of moving towards a major volcanic eruption and (3) an investigation of the subduction zone in Peru where the present day plate structure will be related to the fluid composition of the crust and mantle. This third study will be used to better understand the geological processes that led to the present day distribution of resources. ***The results will give valuable new information to scientists modelling the processes that occur at subduction zones. This includes the properties of the crust and mantle and the composition and time variations of shallow magma chambers that may cause large eruptions. This research will benefit Canada by helping to develop geothermal resources in Western Canada, and thereby reducing dependence on fossil fuels. It will also develop improved imaging methods that can be used in the geothermal and mineral industries. The studies in South America will help understand the behaviour of subduction zones, with an emphasis on the behaviour of magma bodies prior to volcanic eruptions and the angle at which plate subduction occurs. Part of Canada's Pacific coast is located above a subduction zone, and the new results will give an improved context for the phenomena and hazards associated with this plate boundary. An additional benefit will be the training of graduate students in these methods who will be qualified to work as geophysicists in the geothermal, mineral and hydrocarbon industries. **