How earthquakes create most of the world's gold deposits
It turns out it doesn't take a fairy-tale goblin to spin gold. All you need is a considerable dose of seismic activity.
How gold actually forms has always been something of a mystery. Some studies suggest the metal came from meteorites pelting the planet long ago. Others show that the element can be drawn from the excrement of toxin-gobbling bacteria.
But a new study conducted by Australian geologists may have cleared the field. According to a report published Sunday in Nature Geoscience, more than 80 percent of the world's gold deposits were formed due to ground-rattling earthquakes. "Geologists have long known that gold seams must form when mineral-rich water flows through networks of cracks in rocks 5 to 30 kilometers below the ground," says Jeff Hecht at New Scientist. "But exactly how the gold accumulates in these cracks was unclear."
In other words: How did all that mineral-rich fluid transform into the gleaming metal of choice for connoisseurs of fine jewelry everywhere? Hecht explains:
Using a simple model, geologists have shown that mountain-building earthquakes deep below Earth's surface pull apart rocks so quickly that the high-pressure fluids they contain instantly vaporize. This process leaves behind residues rich in minerals including gold. [New Scientist]
This process, termed "flash vaporization," occurs as far as 18 miles below the surface. A big earthquake can deposit "as much as 0.1 milligrams of gold along each square meter of a fault zone's surface in a faction of a second," says io9. Researchers estimate that "active faults can produce a 100-metric-ton deposit of gold in less than 100,000 years."