EMinar 4.2 - Alan Jones - Discovering/imaging mineral systems at all scales using natural-source EM

Meeting the technological demands of the future—especially achieving NetZero targets by 2050—requires discovering new mineral resources at an unprecedented pace. These must include not only critical minerals but also base metals such as copper, which remain essential yet are often underappreciated in energy transition discussions. Copper poses a particularly urgent challenge. While current global production is approximately 20 million tonnes per year (Mt/year), projections for 2050 estimate demand will rise to between 35 and 50 Mt/year. This widening supply gap is worsened by the expected closure of nearly 200 major copper mines by 2035, declining ore grades in existing operations, and a limited pipeline of new projects forecast to add only 2 Mt/year. With most easily accessible deposits already discovered, exploration must advance into deeper and more geologically complex terrains. To achieve this, exploration strategies must evolve. A paradigm shift from deposit-scale targeting toward understanding entire mineral systems is now underway. This approach, based on the Mineral Systems concept of McCuaig and Hronsky (2014) and the Minerals Targeting framework of Begg (2015), focuses on mapping the broader lithospheric architecture controlling mineralization. From a geophysical perspective, this involves a hierarchical exploration strategy. Deep-probing geophysics is used to image lithospheric-scale structures and identify potential fluid sources. Crustal-scale probing then delineates prospective “camp-scale” fluid reservoirs, followed by shallow-probing methods that target individual ore bodies at economically viable depths. Natural-source electromagnetic (NSEM) methods—encompassing both ground-based and airborne techniques—can contribute significantly at all three spatial scales. This paper critically reviews the capabilities, strengths, and recent developments in NSEM methods within this mineral systems framework.