what is the connection
One possible explanation is related to earthquakes and electricity. More details on this with examples and proofs – under the cut.
Piezoelectric effect and gold deposits
It all starts with the piezoelectric effect that occurs during earthquakes. This is the effect of the polarization of a dielectric under mechanical stress (direct piezoelectric effect). That is, under the pressure that occurs during earthquakes, some minerals begin to generate an electric charge. An example is quartz.
Australian scientists assumedthat it is this process that contributes to the accumulation of gold. Electricity triggers physical and chemical reactions that lead to the precipitation of gold from the surrounding solutions. The hypothesis seems realistic: it can be used to explain how native precious metal is formed.
What does quartz have to do with it?
Quartz has piezoelectric properties and can generate electric potential under mechanical influence, for example, during earthquakes. This property is associated with the structural features of its crystals: they have no center of symmetry.
Current generated during earthquakes, starts interact with surrounding liquids, in particular, with hydrothermal solutions containing gold ions. Chemical reactions occur that lead to the deposition of metal on the surface of quartz crystals. The more gold settles, the more active the further process is.
It is precisely these processes that lead to the formation of gold dendrites in low-sulfide epithermal deposits. In places like the McLaughlin Gold Mine in California, gold formed dendritic structures within a silica gel that eventually turned into quartz over time. The gel served as a framework for the formation of gold dendrites, and gold gradually accumulated within, forming future nuggets.
In the Norilsk deposit, gold appears in the same way. Large nuggets are found here in areas with a high content of piezoelectric minerals: quartz, clay, and so on. In Australia, for example, large gold nuggets are also found at the Tyne Tyne mine – this is due to tectonic activity in the region. In all these cases, the piezoelectric effect and tectonic processes lead to the formation of gold deposits.
The process of gold deposition is directly related to stresses that arise in zones of active faults in the earth's crust. In these places, electromagnetic fields are often generated, which can serve as precursors to earthquakes.
Models created by scientists show that electric fields can arise several hours before an earthquake. This happens if the fault contains materials with a high piezoelectric coefficient – the same quartz and clay. Then electricity initiates the processes of gold precipitation from solutions, concentrating the metal on the surface of the crystals.
More found outthat the piezoelectric effect can occur in places where one part of the earth's crust descends relative to another. And in shear zones, where rocks are displaced horizontally. This confirms the universality of the mechanism in areas of tectonic activity.
What about the evidence?
To test the hypothesis, a joint team of scientists from Monash University, CSIRO and the Bragg Institute conducted a series laboratory experiments. Scientists immersed quartz crystals in solutions containing gold ions and subjected them to mechanical stress that simulated earthquakes. The results showed that after just an hour, small deposits of gold began to form on the surface of the quartz. It is important to note that the metal was deposited precisely on those areas of the crystals where there were already traces of metal. This confirms the self-sustaining nature of this process.
In addition, studies have shown that colloidal gold, which is tiny particles of metal, can remain stable in hot hydrothermal fluids at temperatures up to 350 °C. In such solutions, the concentration of gold is thousands of times higher than the average level. This means that, in addition to the usual precipitation of gold as a result of chemical reactions, the smallest particles of the metal are also important. They can accumulate in large quantities in natural conditions and contribute to the formation of rich gold placers.
Scientists have noted that quartz in natural deposits often occurs as disordered crystals, i.e. with a less regular or chaotic structure of atoms. This can reduce the effectiveness of the piezoelectric effect, since a less organized structure affects the properties of the crystal. However, gold is deposited on more ordered crystals, where the atomic lattices are more systematic and organized. This explains the formation of large nuggets in orogenic deposits.
The next stage of the research is to study the rate of gold deposition in different geological settings. Additional long-term experiments will be needed, but the results will give us a better understanding of how tectonic processes and electrical fields are related to the formation of gold nuggets.
Tell us in the comments which hypotheses seem realistic to you.
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