For decades, scientists have been puzzled by the formation of large gold nuggets found within quartz veins. While gold naturally occurs within quartz, the second most abundant mineral on Earth, these nuggets often cluster in massive formations, a phenomenon that has long defied explanation.
Chris Voisey, a geologist at Monash University in Australia, led a groundbreaking study published in the journal Nature Geoscience, finally unveiling the secrets behind these gold nuggets. The key lies in the interplay between earthquakes and the piezoelectric properties of quartz.
Quartz veins are fractures within quartz-rich rocks that are periodically filled with hydrothermal fluids carrying gold atoms from deep within the Earth’s crust. While these fluids should theoretically distribute gold evenly, the presence of large nuggets indicates a different mechanism at play.
Voisey and his team discovered that these nuggets are predominantly found in orogenic gold deposits, formed during earthquakes. Crucially, quartz is a piezoelectric mineral, meaning it generates an electric charge in response to stress, such as the pressure generated by earthquakes.
During an earthquake, the seismic forces fracture rocks and push hydrothermal fluids into quartz veins. This stress also triggers the piezoelectric effect in quartz, creating an electric charge that interacts with dissolved gold, causing it to precipitate and solidify.
The researchers found that gold preferentially solidifies onto pre-existing gold grains, acting as an electrode for further reactions, further concentrating the gold. This process, fueled by the piezoelectric effect of quartz during earthquakes, explains the formation of large, concentrated gold nuggets.
To test their theory, the researchers conducted a laboratory simulation, replicating seismic waves and the piezoelectric effect in quartz crystals submerged in a gold-containing solution. The experiment successfully confirmed their hypothesis, demonstrating that quartz can generate sufficient voltage to precipitate gold under geological stress.
This breakthrough has important implications for understanding the formation of these valuable gold deposits and potentially for developing new methods to identify and extract gold. While scientists now understand the process, it is unlikely to lead to direct gold mining in the near future. However, the research offers new tools for detecting piezoelectric signals from quartz deep underground, helping geologists pinpoint areas with potential quartz veins.
