Geologists uncover ‘Goldilocks Zone’ for precious metals in Earth’s crust

Leicester research has identified a new ‘Goldilocks Zone’ in the Earth’s crust which could provide metals vital to the green revolution.

The energy future of humankind depends on the continued supply of key metals like gold, copper and tellurium that are essential in the manufacturing of green technology, such as battery storage devices, solar panels and wind turbines.

Now, a new international study led by researchers from the Centre for Sustainable Resource Extraction at the University of Leicester, published today (Monday) in Nature Communications, and funded by the Natural Environment Research Council (NERC), has discovered the presence of a temperature dependent ‘valve’ located at the base of the Earth’s crust, which intermittently allows these important metals to pass upwards to shallower levels.

Critical metals required to enhance the green energy revolution are largely stored in the mantle of our planet, at depths in excess of multiple tens of kilometres that are inaccessible to direct extraction.

Fortunately, every now and then, nature does most of the hard work for us. Magmas sourced from within the Earth’s mantle rise up into the crust and have the potential to carry, and then concentrate and deposit, large volumes of metals.

Dr David Holwell is an Associate Professor in Applied and Environmental Geology and lead author for the study. He said: “When magmas reach the base of the crust, the conditions there act like a ‘Goldilocks Zone’ for these metals. If the temperature is either too hot or too cold, these ‘valves’ remain shut and metals cannot pass through, but we have found that in many cases, it may be ‘just right’ at around 1,000°C, where metals like copper, gold and tellurium can be released.”

This finding sheds light on the planetary cycle of metals and how some of the world’s largest resources of copper are formed. The work is part of the NERC-funded FAMOS project (From Arc Magmas to Ores), and involved collaborators from Cardiff University, the University of Western Australia and the mining company BHP.

Professor Jamie Wilkinson, of the Natural History Museum, London, is Principal Investigator for the FAMOS project, and added: “This paper represents a fantastic piece of work from the project team that sheds new light on magmatic processes that operate deep in the Earth’s crust but which have major implications for the accessibility of critical metals for humankind. The results will enable more targeted mineral exploration, thus lowering the environmental footprint associated with the discovery and extraction of green metals.”

‘Mobilisation of deep crustal sulfide melts as a first order control on upper lithospheric metallogeny’ is published in Nature Communications.