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 electric charge when subjected to stress. This phenomenon is already familiar to us in everyday items like quartz watches and BBQ lighters, where a small mechanical force creates a significant voltage. What if the stress from earthquakes could do something similar within the Earth?
To test this hypothesis, researchers conducted an experiment designed to replicate the conditions quartz might experience during an earthquake. They submerged 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 the Monash University School of Earth, Atmosphere and Environment.
"The stressed quartz not only electrochemically deposited gold onto its surface, but it also formed and accumulated gold nanoparticles," he said.
"Remarkably, the gold had a tendency 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.