Science could guide the next gold rush

Gold explorers could soon be guided by research conducted by a Geoscience Australia-led team that has uncovered previously unknown patterns in global geology.

Researchers from Geoscience Australia’s Exploring for the Future program, the University of Adelaide and the United States Geological Survey had compared magnetotelluric data from across Australia, North and South America and China for the first time to identify the patterns.

“Like a live wire detector, magnetotelluric instruments identify natural electric conductors in the Earth from tens to hundreds of kilometres beneath the Earth’s surface that are sometimes linked to copper, gold and associated critical mineral deposits,” Exploring for the Future senior science advisor Dr Karol Czarnota explained.

“Through this analysis, we’ve found that we can pinpoint areas for exploration by using statistics to look through the whole tectonic plate and identify which conductors have the greatest potential to be associated with mineral deposits.

“This is the first time we have identified statistically robust, global insights of this kind, which image the source regions of minerals deep in the crust and pinpoint favourable areas for exploration.”

The key takeaway for gold explorers looking for a hand up is that the team’s findings have indicated that there is a “sweet spot” which would make it much easier to zoom in on new prospective ground and spark off a new gold rush.

Dr Czarnota added that information could also be used to find other vital resources such as copper, tellurium, antimony and other critical minerals.

With the growing move towards electrification, the research could aid in the discovery of new resources required to keep this momentum.

Orogenic gold source

The team’s paper published this week in the journal Nature Scientific Reports also sheds light on the source of gold in orogenic gold deposits, which are formed in mountain-building zones and are responsible for more than 75% of the precious metal recovered to date.

“We’ve learnt that gold in orogenic gold deposits is most likely sourced from the mid to lower part of the Earth’s crust as opposed to the even deeper layer in the Earth, the mantle,” Dr Czarnota said.

“This answers the question of where the gold in deposits that helped build towns like Ballarat and Bendigo came from.”

Australian data gathering

The research drew on data from the Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP), which is a partnership between Geoscience Australia, state and territory geological surveys, AuScope and universities to acquire magnetotelluric data across the Australian continent.

So far, the national AusLAMP project, which was launched in 2013, has modelled the underlying geology of more than 2.5 million km2 across Australia, revealing electrical conductors and resistors that extend deep below the Earth’s surface.

This is less than half of Australia’s 7.692 million km2 land area.

“We know 80% of the Australian continent is ‘undercover’ – which means some of the best geology containing mineral, energy and groundwater resources is hidden under a blanket of younger sediments,” Dr Czarnota said.

“Magnetotellurics is one of the few techniques that can ‘see’ through this cover. This technology is a powerful tool for mineral exploration – using it, we are basically learning how to read nature.”