Gold is literally transported to the Earth's surface using fire and brimstone.
By Michelle Starr
The sulfur that bubbles beneath active volcanoes is essential to the mechanisms that bring gold
to the surface from deep below the Earth's mantle.
According to two recent studies, certain types of sulfur create molecular interactions with gold
that would otherwise keep the valuable metal trapped in the mantle, enabling it to rise.
The form of sulfur that matters most is what they can not quite agree on.
Trisulfur is crucial, according to studies and computer modeling carried out by a group of
geologists from the China University of Geosciences under the direction
of Deng-Yang He. However, bisulfide is the key component, according to research done
by Stefan Farsang and ZoltĂĄn Zajacz of the University of Geneva.
Both sets of findings are intriguing and need further investigation since we may maximize
the use of this lovely, priceless, and practical resource by comprehending how gold deposits
are formed.
At the intersections of tectonic plates, gold deposits are frequently linked to volcanic activity.
A subduction zone is created there when the edge of one tectonic plate slides beneath the plate
next to it.
The Pacific Ring of Fire, a lengthy chain of volcanoes, is one example of the region rife with
earthquakes and volcanoes due to interactions between the two plates.
The gold found in these deposits comes from the mantle, which is located far below the surface
of the Earth. The thick metal would remain there if left to its own devices, but it is deposited there after
becoming part of the magmas that rise to the surface due to volcanic activity.
Sulfur is thought to be the secret to its transportation.
Gold and other heavy metals have a strong affinity with sulfur.
However, there is disagreement among Earth scientists on the shape that sulfur takes in order to
move gold through the subduction zones of the planet. Deng-Yang In order
to create a thermodynamic model that could forecast the actual circumstances that
lead to gold movement, he and his associates experimented with various pressures
and temperatures.
They discovered that gold and trisulfide combine to produce a soluble complex with the
formula Au(HS)S3– at a set of extremely precise temperatures
and pressures where water is heated and oxidized as the Earth's crust sinks.
Their calculations demonstrated that this complex can carry concentrations of gold of several
grams per cubic meter of fluid, which is more than three orders of magnitude greater than the
usual amount of gold found in the Earth's mantle.
This method of slurping the gold from the mantle and pouring it onto the crust is incredibly
effective. Adam Simon, a geologist at the University of Michigan, states, "This thermodynamic
model that we have now published is the first to demonstrate the presence of the
gold-trisulfur complex that we previously did not know existed at these conditions."
"In subduction zone conditions, this provides the most likely explanation for the extremely
high quantities of gold in some mineral systems."
However, there can be other options for transportation.
Farsang and Zajacz discovered a method to adjust the sulfur's oxidation state in their experiment
at the University of Geneva by subjecting it to pressure conditions and temperatures of 875 degrees
Celsius (1607 Fahrenheit), which is comparable to the temperature of natural magmas.
Prior studies, such as a highly referenced 2011 study, had demonstrated that trisulfur was in
charge of the transport.
The new findings demonstrated the high presence of sulfur dioxide, hydrogen sulfide,
and bisulfide at magmatic temperatures.
This is intriguing since bisulfide contributes to the movement of metals in
lower-temperature hydrothermal fluids.
Although it was previously believed that bisulfide could not exist at magmatic temperatures,
Farsang and Zajacz's research revealed that it could.
Farsang claims that by carefully selecting our laser wavelengths, "we also demonstrated
that the number of sulfur radicals in geologic fluids was significantly overstated in earlier
research and that the 2011 study's results were actually based on a measurement artefact,
putting an end to this controversy."
Source sciencealert.com
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