A challenge for the global mineral exploration industry is to identify world-class deposits, often deep under thick layers of sedimentary cover. Traditional approaches target the small-scale economic ore deposit, with declining rates of success over past decades. However, an alternative approach is to image deeper parts of the Earth's crust to find a much larger footprint where the metals originated. By finding the deep source we can also map potential pathways through the upper crust to define new prospective areas beneath sedimentary cover. So, rather than looking for the needle, it is better to first identify the haystack.
The magnetotelluric (MT) method yields electrical resistivity images that provides insight into the current thermal and geochemical composition of the crust and upper mantle. As such properties result from past tectonic and metamorphic events, the current resistivity profile is a record of the integrated events over deep time and their preservation. In this talk I´ll show how the MT technique spans the exploration scale-lengths from continental-scale lithosphere-asthenosphere boundary to thickness of sedimentary cover, and thus is well placed to image an entire mineral system.
Graham has over 25 years of experience using magnetotellurics, or MT for short. His group at the University of Adelaide has run the Australian national AuScope MT facility for the last ten years, and is involved in a wide range of research activities, including the national MT mapping program AusLAMP, and 4D monitoring of fluids for hydrocarbon and geothermal energy development