Resources for tomorrow – how airborne geophysics can contribute for the exploration of deep mineral deposits

Economies are critically dependent on the secure provision of raw materials. The EU commission currently lists 30 elements as critical, including base metals as well as high-tech metals. Projections indicate a significant increase in demand within the next decades, in parts due to the transformation of the energy sector and the digital revolution. Therefore, reuse of raw materials in the context of circular economies must be accompanied by the development of additional primary resources. Furthermore, to minimize dependencies from individual producing countries, the supply chains must be diversified, including the exploitation of domestic resources. Consequently, exploration activities - of which geophysics is a critical component - must be intensified today to increase the reserves for tomorrow.

New deposits are likely to be found under cover and at depths greater than has typically been exploited in the past. Both greenfield and brownfield environments, such as historic mining districts, have a potential for new discoveries. Recent developments in airborne geophysics aim at increasing the exploration depth and improving the imaging capabilities to detect targets that have previously remained hidden. In this lecture, I will discuss the challenges for airborne geophysical exploration, with a particular focus on semi-airborne electromagnetics, a hybrid approach that combines the benefits of powerful land-based transmitter deployments with the dense spatial coverage of overflights with passive airborne receivers. This concept has been implemented in the ongoing DESMEX project and has also received interest elsewhere. The hybrid approach can be shown to exhibit significantly increased penetration depth than classical airborne EM systems. Moreover, without the need to tow heavy transmitters airborne, the concept can be ideally transferred to unmanned platforms, reducing the costs significantly. Finally, three-dimensional inverse modelling becomes tractable with this setup; this is because the number of involved simulation steps per iteration scales with the number of transmitter installations (typically less than ten) instead of the number of measurement points with fixed transmitter-receiver geometries as in classical airborne measurements (typically several thousand). I will present case studies from demonstration measurements in Europe and beyond.