Formation of Massive Gold Nuggets in Quartz Rock: Role of Earthquakes
In the world of geology, the formation of massive gold nuggets within quartz rock has long been a mystery. How can such valuable lumps of metal, sometimes weighing nearly 100 kilograms, form in inert rock without any obvious chemical or physical trap? This enigma has puzzled scientists and researchers for years until now.
Research conducted by Chris Voisey and his colleagues at Monash University in Melbourne has shed light on a possible mechanism that explains the formation of these enormous gold nuggets. The key lies in the unique properties of quartz crystals and the role of earthquakes in creating an electric field that attracts gold dissolved in fluid forced up from deep underground.
The Piezoelectric Nature of Quartz
Quartz crystals are known to exhibit piezoelectric properties, meaning they can produce electricity when subjected to mechanical stress. This phenomenon occurs due to the lack of a center of symmetry in the crystal structure of quartz. When quartz crystals are deformed or put under pressure, they generate a voltage that can attract gold particles that are dissolved in water.
This piezoelectric response of quartz is crucial in understanding how gold nuggets form within quartz rock. The seismic activity caused by earthquakes can trigger this piezoelectric effect in quartz, creating an electric field that draws gold-bearing hydrothermal fluids from Earth’s mid to lower crust up through fissures in the rock.
The Role of Seismic Activity
Gold-bearing hydrothermal fluids are typically found deep underground, around 15 to 20 kilometers below the Earth’s surface. These fluids contain traces of gold, but the concentration is so low that it would take a significant amount of fluid to produce even a small amount of gold. However, during seismic activity, such as earthquakes, these fluids are pushed up through the cracks and fractures in the rock, bringing the dissolved gold closer to the surface.
Voisey and his team hypothesized that the piezoelectricity of quartz plays a crucial role in concentrating gold into nuggets within veins during repeated seismic events. To test this hypothesis, they conducted experiments using quartz crystals placed in a solution containing gold and subjected to moderate pressures. The results were fascinating.
Experimental Findings
The experiments conducted by Voisey and his colleagues revealed that quartz samples subjected to pressure exhibited a piezoelectric response, attracting gold particles from the solution. In contrast, samples that were not put under pressure did not show the same attraction to gold. This confirmed the link between the piezoelectric nature of quartz and the formation of gold nuggets.
Furthermore, the team observed that coating the quartz samples with iridium, a metal that enhances the piezoelectric response of quartz, led to the growth of larger gold pieces. The coated samples attracted gold particles of up to 6000 nanometers in size, compared to only 200 to 300 nanometers for uncoated quartz. This demonstrated the significant impact of piezoelectricity on the formation of gold nuggets.
Once gold particles started depositing on the quartz surface, they acted as a catalyst for more gold to accumulate. Voisey likened this process to a lightning rod, with the gold acting as a conductor that attracts additional gold particles in solution. This rapid accumulation of gold on the quartz surface could explain the formation of massive gold nuggets within quartz rock.
In conclusion, the research conducted by Voisey and his team provides valuable insights into the formation of massive gold nuggets in quartz rock. By understanding the role of piezoelectricity in attracting gold particles during seismic activity, scientists are one step closer to unraveling the mysteries of Earth’s geological processes. The connection between earthquakes, quartz crystals, and gold deposition highlights the intricate relationship between geology and mineral formation, offering new avenues for exploration and discovery in the field of Earth sciences.
