A natural laboratory for critical metals investigations in the Mourne Mountains granites

Abstract

Certain metals that are vital for many modern technologies occur naturally in the Mourne Mountains Complex of County Down, Northern Ireland. These include niobium, tantalum and the rare earth elements. Using the Tellus geochemistry data and the results of more detailed sampling, we have investigated their geological sources in granite bedrock and their dispersion in stream sediments. From this research, an exploration methodology has emerged that can assist in the search for critical metals globally. Planned follow-on studies include investigations of the environmental fate of these metals and the potentially toxic elements with which they are naturally associated. Strategic contextMany new technologies, such as those required for clean energy generation and modern communications, require a wide range of elements in their manufacture. Of particular interest are elements that are used in small quantities but are highly valued for their unusual properties. The mines that produce these economically important metals are mostly located in a few countries where political, social and environmental circumstances could potentially disrupt supply. These technology metals with a substantial supply risk are termed 'critical metals' (Moss et al., 2011). The rare earth elements (REEs) exemplified the concept of criticality when in 2011 China, which controlled 97% of the global REE supply, cut its export quota and caused a shortfall in supply relative to demand (Chakhmouradian and Wall, 2012).Supply shortages cannot be fully offset by increased recycling due to dispersion of critical metals in the environment, longevity of use in some applications, and manufacturing design and alloying with metals that inhibit separation (Steinbach and Wellmer, 2010;Bloodworth, 2014). Other mitigation strategies include substitution, reduction in use