Australian geologists have discovered that gold nuggets form inside quartz deposits due to earthquakes, whose vibrations cause the quartz to generate electricity and reduce gold ions present in underground geothermal fluids. The scientists’ findings were published in a paper in the scientific journal Nature Geoscience.
“We have shown that mechanical deformation of quartz crystals in gold-bearing rocks generates an electrical voltage strong enough to trigger the electrochemical reactions necessary for the formation of gold nanoparticles within gold salt solutions, as well as their subsequent growth and accumulation in the rock. This explains the existence of large gold nuggets, as well as the nature of their appearance in cracks within quartz deposits.” – the study says, citing excerpts from TASS.
This was the conclusion reached by a group of Australian geologists led by a researcher at the Australian Neutron Scattering Centre in Sydney (ANSTO). Vladimir Luzin while studying how quartz deposits and hydrothermal fluids interact with each other. Scientists’ interest in these interactions is due to the fact that all native gold deposits available on Earth were presumably formed in a similar way.
Scientists still cannot say exactly how this happened, but many researchers believe that pure gold is deposited in the form of particles and nuggets when the temperature, pressure and chemical composition of this liquid changes. Luzin and his colleagues proposed an alternative theory, which is based on the fact that quartz is a natural piezoelectric material that produces electric current under various mechanical deformations, including when exposed to seismic vibrations.
The scientists hypothesized that this electricity causes gold ions to react with other molecules, “steal” electrons from them and precipitate out in the form of nanoparticles. Guided by this idea, the scientists placed a layer of quartz rocks and a gold chloride solution inside a special machine that stretched and compressed the mineral at the same frequency as earthquakes, and observed how the appearance of these analogues of gold-bearing quartz veins changed.
These experiments showed that gold nanoparticles quickly appeared between the layers of quartz rocks, which subsequently grew in size to become grains of golden sand with a diameter of several micrometers. This process was significantly accelerated in cases where gold nanoparticles were already present in the formation, indicating their important role in the process of gold deposition and the formation of gold nuggets. Understanding this will help in searching for new gold deposits, the scientists concluded.
