Global
Geological map of the El Laco volcanic complex in northern Chile.
Schematic representation of the formation of iron ore deposits beneath
a volcano. Magma rises towards the surface of the Earth through cracks
in the surrounding rock. When the magma cannot continue its upward
journey, it pools in a magma chamber (yellow oval). The temperature
and pressure in this reservoir make the magma unstable, causing it to
split into two separate liquids: one that is rich in silica and one that is
very rich in iron. As the iron-rich liquid starts to cool, it forms iron ore
deposits (in black).
Created by José A. Naranjo, Fernando Henríquez, Jan O. Nyström. Licensed under CC BY 4.0
(http://creativecommons.org/licenses/by/4.0), via Wikimedia Commons
these findings may help to find new
iron ore deposits. This is necessary
to keep up with the global demand
for iron — recycling alone is not
enough yet. And if you want to know
where to look for iron ore, you have
to understand how the deposits are
formed,” Namur says. b
About the author
Katrien Bollen is the press officer
at the Department of Earth and
Environmental Sciences at the
University of Leuven.
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The samples were placed in small golden
capsules – with a melting point of 1 064°C
– and subjected to temperatures of
1 000–1 040°C and one thousand times the
atmospheric pressure of Earth.
“We were surprised to find that, under
these conditions, the magma split into
two separate liquids. This process is
known as immiscibility. Just think of
what happens when oil spills into the
ocean: the water becomes streaked
with oil because oil and water cannot
mix,” Namur explains.
One of these liquids contained a
lot of silica, whereas the other was
extremely rich in iron — up to 40% —
and phosphorus. When this iron-rich
liquid starts to cool down, you get
iron-phosphorous Kiruna-type ore
deposits. This is the first evidence that
immiscibility is key to the formation
of iron ore deposits such as the ones
mined in El Laco. “If we are right,
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