Earthquakes can cause the mineral quartz to form huge gold nuggets
It was already known that gold forms in the mineral quartz with the help of earthquakes, but now it has been discovered exactly how the tremors act on the mineral to form huge gold nuggets.
Gold is a precious metal that occurs in the Earth's mantle and rises to the earth's surface through geological movements, such as earthquakes. Science already knew that it forms in the mineral quartz with the help of earthquakes, but now, geologists have discovered exactly how earthquakes combine with quartz to form large gold nuggets - finally solving a mystery that has intriguedresearchers for decades.
Quartz is the second most abundant mineral on Earth, second only to the feldspar group.
The findings were recently released in the journal Nature Geoscience. Follow the information below.
Earthquakes and quartzes united to form gold
Gold is formed naturally in quartz, usually grouping into nuggets. These nuggets "float" in the middle of the stone cracks that are periodically pumped with hydrothermal fluids from the depths of the crust.
"Gold forms in quartz all the time. What is strange is the formation of really very large gold nuggets. We didn't know how this worked; how you get a large volume of gold to mineralize in a discreet little place," said Christopher Voisey, a geologist at Monash University in Australia and lead author of the study.
According to the study, these giant gold nuggets are exceptionally valuable and represent up to 75% of all gold ever mined.
Hydrothermal fluids carry gold atoms from the depths and release them through the cracks of the quartz, which means that gold should theoretically spread evenly through the slits instead of focusing on large nuggets, as Voisey explained.
However, the huge gold nuggets formed in another way, and this was discovered by two factors: first because the largest nuggets occur in orogenic gold deposits, which are deposits that form during earthquakes; and second because quartz is a piezoelectric mineral, that is, it creates its own electrical charge in response to the geological stress generated by earthquakes.
But how did the gold nuggets get huge?
According to the study, earthquakes fracture rocks and force hydrothermal fluids into the quartz cracks, filling them with dissolved gold. In response to the geological stress of the earthquake, the cracks generate an electrical charge that reacts with the gold, causing it to precipitate and solidify.
The largest orogenic gold nuggets (formed in quartz due to earthquakes) found so far weigh about 60 kilograms.
So, gold focuses on specific points because "gold dissolved in solution will preferably be deposited in pre-existing gold grains," as the study explains. This means that in quartz fractures, gold solidifies under clusters that already exist and grow with each new tremor. That is, the existing gold grains are the focus of continuous growth.
The researchers tested this in the laboratory, simulating the effect of an earthquake in quartz crystals submerged in a liquid containing gold. Simulation also confirmed that gold solidifies preferentially on top of gold deposits already existing in quartz cracks, and this helps explain the formation of large gold nuggets.
However, this discovery does not give new clues about where to mine gold nuggets. The best that science can currently offer is a device that detects piezoelectric quartz signals in depth.
News reference:
Voisey, C. R. et al. Gold nugget formation from earthquake-induced piezoelectricity in quartz. Nature Geoscience, 2024.