Bandung, IndonesiaSentinel.com — Scientists have discovered how earthquakes can trigger quartz into forming large gold nuggets, a large fragment that contain 75% of gold. This discovery solved a mystery that researchers had been looking for decades.
Gold naturally forms in quartz, which is the second most abundant mineral in Earth’s crust after feldspar. Those golds found in quartz often cluster into giant nuggets, unlike any other types of gold deposits. These nuggets are typically found floating in the middle of what geologists call quartz veins, which are cracks in quartz-rich rocks that periodically get pumped full of hydrothermal fluids from deep within the earth’s crust.
Gold theoretically should become evenly spread in the cracks rather than concentrated into nuggets due to hydrothermal fluids that would carry gold atoms up from the deep and flush them through quartz veins.
“Gold forms in quartz all the time,” said Chris Voisey, a geologist at Monash University in Australia and the lead author of a new study published Monday (Sept. 2) in the journal Nature Geoscience. “But what’s strange is the formation of these really large gold nuggets. Until now, we didn’t understand how you could get such a large volume of gold to concentrate in one small, specific area,” Voisey said, stated from Live Science.
These nuggets are exceptionally valuable and represent up to 75% of all the gold ever mined, according to the study.
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Voisey and his team identified two key clues that helped them unravel the mystery. The first was that the largest gold nuggets are found in orogenic gold deposits, which are deposits formed during earthquakes. The second was that quartz is a piezoelectric mineral, meaning it generates an electrical charge when subjected to geological stress, such as the seismic activity caused by earthquakes.
Gold concentrates in specific spots because “gold dissolved in solution will preferentially deposit onto pre-existing gold grains,” Voisey said. “Gold essentially acts as an electrode, attracting more gold due to the voltage created by nearby quartz crystals.”
This process, according to the research, allows gold to solidify into clusters that grow larger with each earthquake. The largest known orogenic gold nugget weighs around 130 pounds (60 kilograms), Voisey said.
To test their theory, the researchers simulated an earthquake’s effect on quartz crystals in the lab. By submerging quartz in a liquid containing gold and replicating seismic waves, they were able to generate a piezoelectric charge. The experiment confirmed that geological stress can produce enough voltage within quartz to precipitate gold from the solution.
The findings also showed that gold tends to solidify on existing deposits within quartz veins, explaining how these large gold nuggets form.
“Realizing that pre-existing gold acts as a catalyst, attracting more gold to form massive nuggets, was an incredibly exciting discovery,” Voisey said.
(Raidi/Agung)
