Stumbling upon a giant gold nugget and retiring rich is a fantasy for many, but how do these large nuggets actually form? Recent experiments suggest that earthquakes and electricity might be key contributors.
The element gold is dispersed throughout the universe by supernovae and neutron star collisions, not by Earthly processes. Traces of gold get embedded when planets like Earth originate from the ensuing dust storms. The majority of this gold is buried deep within the planet’s core over billions of years, although additional gold may be added by asteroidal impacts and seismic activity that brings it closer to the surface. Gold usually shows up as tiny flakes, but every now and again large nuggets weighing several kilograms show up. The precise mechanism underlying their development has remained somewhat of a mystery up until now. Dr. Chris Voisey, lead author of a new study, explained the prevailing theory: gold precipitates from hot, water-rich fluids moving through cracks in Earth’s crust. As these fluids cool or undergo chemical changes, gold becomes trapped in quartz veins. However, this theory doesn’t fully account for large nuggets, especially considering the low concentration of gold in these fluids.
To explore new possibilities, researchers at Monash University focused on an unexpected factor—electricity. Quartz, a common host for gold, is piezoelectric, meaning it produces electrical charges when stressed. The team hypothesized that the mechanical stress from earthquakes could cause gold to clump together via this effect.
To test this, they simulated earthquake stress on quartz crystals submerged in gold-rich fluids. The results were astonishing: the quartz not only attracted gold but also accumulated nanoparticles, preferentially adding to existing gold grains.
“The quartz acts like a natural battery,” said Dr. Voisey. Each seismic event brings more gold to the grains, slowly growing them into the giant nuggets we sometimes find today. This discovery offers a plausible explanation for the formation of large gold nuggets in quartz veins.
