September 3 () –
The formation of the much sought after giant gold nuggets, which are usually found embedded in quartz veins, It may be related to electricity generated by earthquakes.
This is suggested by research led by Dr Chris Voisey from Monash University’s School of Atmosphere and Earth Environment and to be published in Nature Geoscience.
“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. While this theory is widely accepted, it does not fully explain the formation of large gold nuggets, especially considering that 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: generates an electrical charge when subjected to voltageThis phenomenon is already familiar to us in everyday items such as quartz watches and barbecue lighters, where a small mechanical force creates a significant voltage. What if the stress from earthquakes could do something similar inside the Earth?
To test this hypothesis, the researchers conducted an experiment designed to replicate the conditions that quartz might experience during an earthquakeThey immersed quartz crystals in a gold-rich fluid and applied voltage using a motor to simulate the shaking of an earthquake. After the experiment, the quartz samples were examined under a microscope to see if gold had been deposited.
“The results were surprising,” 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 also formed and accumulated gold nanoparticles. Surprisingly, the gold had a tendency to deposit on top of existing gold grains rather than forming new ones,” he said.
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 “coating” 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.
As quartz is subjected to repeated stress from earthquakes, it generates piezoelectric voltages that can reduce dissolved gold from the surrounding fluid, which causes it to be deposited.
Over time, this process could lead to the formation of significant accumulations of gold, ultimately producing the huge nuggets that have captivated treasure hunters and geologists alike.
“In essence, quartz acts as a natural battery, with gold as the electrode, slowly accumulating more gold with each seismic event.”Dr. Voisey said.
This process could explain why large gold nuggets are so often associated with quartz veins formed in earthquake-related deposits. This new understanding of gold nugget formation not only sheds light on a long-standing geological mystery, but also highlights the interrelationship between physical and chemical processes on Earth.
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