Electricity generated by earthquakes could be the secret to giant gold nuggets

Scientists have long been fascinated by how gold nuggets, often nestled within quartz veins, form. New research from geologists at Monash University suggests the process may be even more electrifying than we previously thought – literally.

Gold nuggets, prized for their rarity and beauty, have been at the heart of gold rushes for centuries.

The study is led by Dr Chris Voisey from Monash University’s School of Earth Atmosphere and Environment and will be published in Geosciences of nature.

“The standard explanation is that gold precipitates from hot, water-rich fluids as they flow through cracks in the Earth’s crust,” Dr. Voisey said.

“As these fluids cool or undergo chemical changes, the gold separates and becomes trapped in quartz veins,” he said.

“Although this theory is widely accepted, it does not fully explain the formation of large gold nuggets, especially since the concentration of gold in these fluids is extremely low.”

The research team tested a new concept: piezoelectricity. Quartz, the mineral that typically hosts these gold deposits, has a unique property called piezoelectricity: it generates an electrical charge when stressed. This phenomenon is already familiar to us in everyday objects like quartz watches and barbecue lighters, where a small mechanical force creates a large voltage. What if the stress caused by earthquakes could have a similar effect on Earth?

To test this hypothesis, the researchers conducted an experiment designed to replicate the conditions quartz might experience during an earthquake. They immersed quartz crystals in a gold-rich fluid and applied stress using a motor to simulate the shaking of an earthquake. After the experiment, the quartz samples were examined under a microscope to see if any gold had been deposited.

“The results were stunning,” said study co-author Professor Andy Tomkins, from Monash University’s School of Earth, Atmosphere and Environment.

“The stressed quartz not only electrochemically deposited gold on its surface, but it also formed and accumulated gold nanoparticles,” he said.

“It is remarkable that the gold tended to deposit on existing gold grains rather than forming new ones.”

This is because, while quartz is an electrical insulator, gold is a conductor.

Once some gold is deposited, it becomes a focal point for further growth, effectively “plating” the gold grains with more gold.

“Our discovery provides a plausible explanation for the formation of large gold nuggets in quartz veins,” said Dr. Voisey.

When quartz is subjected to repeated stresses during earthquakes, it generates piezoelectric voltages that can reduce dissolved gold in the surrounding fluid, causing it to be deposited.

Over time, this process could lead to the formation of large accumulations of gold, eventually producing the massive nuggets that have captivated treasure hunters and geologists.

“Essentially, quartz acts like a natural battery, with gold as the electrode, slowly accumulating more gold with each seismic event,” Dr. Voisey said.

This process may explain why large gold nuggets are so often associated with quartz veins formed in earthquake-related deposits.

This new understanding of how gold nuggets form not only sheds light on a long-standing geological mystery, but also highlights the interrelationship between Earth’s physical and chemical processes.