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The secret role of seawater in gold formation

Imagine a world where gold is not just found on the surface, but also deep below the ocean floor. This idea may sound straight out of a fantasy novel, but recent research hints at this fascinating possibility.

Scientists have discovered a vital role that seawater plays in the formation of gold, one of our planet’s most precious materials.

A team of scientists journeyed to the isolated Brucejack gold deposit in northwestern British Columbia, where they set out to gather and study ancient ore-bearing rocks.

The deposit, now on land as a result of plate tectonic processes, originally formed in a submarine oceanic island arc about 183 million years ago. The rigorous analysis revealed that these valuable geological relics bore the mark of the mighty seas.

The team discovered that seawater had seeped into the Earth’s crust, mingling with ore fluids and eventually leading to the formation of gold.

Study co-author Anthony Williams-Jones is a professor in the Department of Earth and Planetary Sciences at McGill University.

“These rocks, dating back to the Early Jurassic period, are hosted in volcanic and sedimentary formations,” said Professor Williams-Jones.

“Using high-resolution mass spectrometry, we decoded their unique chemical signatures. The finding of seawater-triggered gold deposition is novel and surprising.”

Finding gold in curdled milk

This discovery is not a standalone revelation. It builds upon earlier research that drew an unexpected parallel between gold formation and the everyday process of milk curdling.

The researchers found that gold nanoparticles clump together, similar to proteins in milk, forming gold deposits.

The cause of this golden congregation, it turns out, can be traced to sodium ions present in seawater. The ions provoke the gold nanoparticles to merge, akin to the action of acid in souring milk.

“In our new study, we discovered that sodium ions in seawater cause gold nanoparticles to clump together, acting like the acid in souring milk and eventually forming gold veins,” noted lead author Duncan McLeish.

Golden opportunities below the sea surface

This revolutionary research was carried out in collaboration with experts from the University of Alberta. The study offers new insights into how gold forms and opens up exhilarating prospects for gold mining.

The work suggests that veins of gold could develop in the seabed, indicating that submarine island arcs and deep ocean trenches ideal for gold formation might be home to unexplored gold resources.

Gold holds immense value – not just for its age-old status as a precious metal – but also for its role in modern applications such as green-energy technologies, electronic devices, and medical equipment.

Land-based mines often offer low-grade ore that demands intensive processing, posing significant environmental costs. Discovering high-grade deposits in the ocean’s depths could help mitigate the environmental effects of gold mining.

“Our findings suggest it may be easier to form the rare but spectacular concentrations of gold found in high-grade gold veins in sub-seafloor settings,” said Professor Williams-Jones.

“With recent interest in mining submarine mineral deposits, our research suggests that Earth’s oceanic crust may indeed contain resources, many of which are required for the green-energy transition, at a level never before appreciated.”

Challenges of deep-sea mining

While the potential for discovering high-grade gold deposits under the sea is thrilling, it also comes with significant challenges and ethical considerations.

Deep-sea mining poses risks to marine ecosystems, which are often less understood than terrestrial ones. The disruption of the sea floor could affect the habitats of various marine species, many of which are yet to be studied.

Additionally, the logistics of extracting minerals from such remote and harsh environments present technical and financial hurdles.

Environmentalists urge caution, emphasizing the need for comprehensive impact assessments and stringent regulations to protect marine biodiversity.

As we advance toward potential underwater mining, balancing technological progress with environmental stewardship will be crucial.

The dialogue between scientists, environmentalists, policymakers, and industry stakeholders will shape the future of this burgeoning field, ensuring that the treasures of the deep are managed responsibly for generations to come.

The study is published in the journal Proceedings of the National Academy of Sciences.


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