When strained by earthquakes, underground networks of quartz veins can generate sufficient voltage to grab gold from passing fluids, researchers report September 2 in Nature Geoscience. The findings clarify how fluids carrying meager quantities of gold can concoct massive nuggets, even in chemically inert settings.
“You discover a 2-meter-wide quartz vein, and there’s an enormous gold nugget proper within the center, and nothing round [that] it might have reacted with,” says geologist Christopher Voisey of Monash College in Melbourne, Australia. “That’s a conundrum.”
A lot of the world’s gold is mined from networks of branching mineral layers — or veins — made principally of quartz, referred to as orogenic gold deposits. These deposits are constructed piecemeal by earthquakes, normally round six to 12 kilometers underground. The temblors open fractures, that are then infiltrated by subterranean fluids that deposit quartz and gold, forming veins. Subsequent quakes create extra fractures and reopen current veins, incrementally swelling and ramifying the deposit over time.
Geologists have proven how this course of can kind small and diffuse portions of gold, however not how the steel turns into concentrated in massive nuggets, Voisey says. The fluids concerned include meager quantities of gold, and quartz is an unreactive medium.
Voisey and colleagues hypothesized that the important thing was quartz’s piezoelectricity, or its capacity to develop electrical cost when strained. They plunged quartz slabs into options containing dissolved gold or gold nanoparticles and used actuators to strike a few of the submerged slabs at a frequency of 20 hertz, mimicking small quakes (SN: 4/12/23).
The putting generated voltages as much as 1.4 volts, inflicting gold grains to mixture on the slab surfaces. No gold deposited on slabs that weren’t struck.
When the experiment was repeated with a piece of a gold-quartz vein, gold deposition turned focused on the already current gold, Voisey says. The prevailing gold adopts the voltage of the charged and fewer conductive quartz, attracting extra gold to itself and concentrating the mineralization, he explains. “It’s like a lightning rod for additional response.”
