2024-08-08 04:00:08
Understanding how gold is formed is crucial to knowing where to find gold and how to mine it in an environmentally friendly way. Researchers at McGill University have answered a long-standing question among geologists, and their findings could lead to the discovery of deposits.
Credit: Duncan McLeish
Researchers traveled to the Brucejack gold mine in northwestern British Columbia to study very old mineralized rocks and collect samples. Now located on the Earth’s surface due to activity plate tectonicsthe deposit was formed in a volcanic arc submarineabout 183 million years ago. After analyzing the samples at theMcGill University and to theUniversité From Alberta, researchers found thatsea ​​water had combined with mineralizing fluids in the earth’s crust to form gold. “These rocks, which date back to the Early Jurassic period, were trapped in sedimentary and volcanic formations,” explains one of the study’s co-authors, Anthony Williams-Jones, Logan Professor of Geology and Geochemistry in the Department of Earth and Planetary Sciences at McGill University. “Using the mass spectrometry At high resolution, we were able to decode their unique chemical signature. Finding gold deposits formed from seawater was unprecedented and unexpected.”
A phenomenon similar to milk curdling In 2021, the McGill University team had already made a discovery that offered some answers. The researchers had observed that gold nanoparticles combined to form high-grade gold deposits, much like proteins clump together to create lumps when milk sours.
“In our new study, we found that sodium ions in seawater played the same role that acid does in milk curdling by causing gold nanoparticles to cluster into veins,” says lead study author Duncan McLeish, a postdoctoral fellow in McGill University’s Department of Earth and Planetary Sciences.
Presence of very high grade gold in the Brucejack mine.
Credit: Duncan McLeish
The presence of seawater suggests that gold-bearing veins could form on the ocean floor. Unsuspected gold deposits could therefore exist in submarine volcanic arcs and ocean trenches, where conditions are ideal, according to the study published in the journal Proceedings of the National Academy of Sciences of the United States of America.
The Ocean, a Promising Vein Historically considered a precious metal, gold has become an essential metal since it is used in green energy technologies, electronic devices and medical equipment, among others. The ore extracted from land mines is often poor and requires considerable processing, associated with a significant environmental cost. On the other hand, the extraction of possible high-grade deposits discovered in the deep sea would reduce the ecological footprint of gold mining, according to the researchers.
“Our observations suggest that the ocean floor may support the formation of rare but spectacular concentrations of gold, such as those we found in high-grade veins. The exploitation of subsea deposits is gaining increasing attention. Our study raises the possibility that the ocean crust contains many of the resources needed to green the energy sector, and in unsuspected quantities,” says Professor Williams-Jones.
References:
L’article “Extreme shifts in pyrite sulfur isotope compositions reveal the path to bonanza gold”, par McLeish, D. F., Williams-Jones, A. E., Clark, J. R. et Stern, R. A., a été publié dans la revue Proceedings of the National Academy of Sciences (PNAS) en mai 2024.
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