Almost all of Earth’s commercial gold has been formed in earthquakes.
The quakes, deep below the surface, rip rocks apart so quickly that the high-pressure fluids inside instantly vaporize. The residue left behind after this violent action is chock full of minerals, including gold.
Studying this rock vaporization is Richard Henley of the Australian National University in Canberra and Dion Weatherly of the University of Queensland in Brisbane. The two study earthquake dynamics, and have found that these earthquakes can open up a vein in subterranean rocks at the speed of sound. It’s this process that produced over 80 percent of the world’s gold.
As Henley explains, when an earthquake rips a hole in a rock, the surrounding fluid cannot fill the void created by the quake fast enough. This causes the pressure in the rocks to drop from 3000 times atmospheric pressure to pressures similar to those found on Earth’s surface. Just like an insanely high power pressure cooker, the fluids are instantly vaporized, depositing its minerals into the surrounding rocks.
“Large quantities of gold may be deposited in only a few hundred thousand years,” Weatherley told New Scientist. “Each event drops a little more gold,” added Henley. “You can see it microscopically, tiny layer after tiny layer. It just builds up.” By geological standards, hundreds of thousands of years is a short period.
This is certainly not the first study linking gold deposits and earthquakes, according to geologist John Muntean at the University of Nevada in Reno.
“But this paper quantifies the amount of pressure drop, and ties it into gold solubility and why that pressure drop could drop out all of the gold in the hydrothermal fluid,” he said.
