Imagine a volcano which emits 20 tons of gold each year as a gas which is then almost all
precipitated into a gold rich ore mineral.
This might sound like science fiction, but what I just descibed actually occurred, albeit
with a different element which is even rarer than gold.
Not only is it rarer than gold, but it is one of the rarest stable aka non radioactive
elements in the Earth's crust.
What I am referring to is the element rhenium, aka element number 75 between tungsten and
osmium on the periodic table, where an abundance of this incredibly rare element is produced
each year via the mineral rheniite.
This valuable mineral occurs in tight clusters of a silvery to black metallic mineral which
is by weight 74.38% rhenium.
Due to its rarity, it is somewhat valuable, meaning that each ounce of rheniite is as
of the making of this video worth 33.74 in US dollars.
However, do not go onto the Kudryavy volcano or its surrounding area to take mienerals
and/or rocks as that is not allowed and it in my opinion appears that some entity already
owns the mining rights on this volcano.
The rheniite occurs in clusters of material adjacent to very hot fumaroles, some of which
are consistently more than 300 degrees Celsius, with the mineral precipitating from fumarole
gasses at the volcano.
However, chemists in my audience might note that rhenium has the second highest boiling
point of any element, requiring more than 10,000 degrees Fahrenheit or 5,538 Celsius
to turn it into a gas.
Yet, the lavas the Kudryavy volcano can produce are generally no more than 2,192 degrees Fahrenheit
or 1,200 degrees Celsius.
So, what exactly causes this element to boil away and turn into a gas?
The answer is not some exceptionally hot layer deep in the Earth's mantle but rather relates
to the secondary element rheniite is bound with due to its chemical formula of ReS2,
sulfur.
Generally speaking, when a mineral contains two elements at varying concentrations, the
relevant melting and boiling points of that mineral are generally less than that of one
of the elements in contains.
The same thing applies for a hypothetical solid solution of a mineral with the elements
rhenium and sulfur which might look something like this.
Thus, this hypothetical temperature falls within the known range of temperatures fumaroles
and magma/lava can produce, allowing for rhenium as an element to melt and become a gas.
But, why might there be so much rhenium as an element in the first place, since the deposit
on the surface in my opinion represents remobilized rhenium from deeper in the crust?
This aspect is uncertain, but I propose one possibility.
At depth there might be a massive sulfide deposit with a large molybdenum rich ore body.
This ore body in turn might be getting melted by volcanic gasses, magma, or residual heat
from both, which is turn releases minute concentrations of rhenium present in the ore into a concentrated
gas which then rises to the surface where it is deposited.
I say this because rhenium as an element is traditionally mined as a very rare but present
byproduct of some molybdenum ores.
This is somewhat supported by the occurrence of molybdenum minerals in the same field of
fumaroles.
Despite the fact that this volcanic complex has a potential for explosive eruptions, and
last erupted in 1999, there is surprisingly an attempt to mine all of this material although
I was unable to find many details on the exact specifications on how this would occur.
Kudryavy is a somma volcano, that is a stratovolcano which grew out of a large caldera.
This caldera formed in a VEI 6 explosive volcanic eruption 410,000 years ago which coated the
landscape in 90 cubic kilometers of volcanic rock, forming a 10.7 kilometer long and 9
kilometer wide caldera.
Through the next several hundred thousand years four different volcanic cones grew along
a east-northeast trending line.
Occasional lava domes erupted, and viscous lava flows covered a section of the once vast
caldera lake which existed.
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