Global
Lab lavas could
Most iron is found in sedimentary rock.
lead to new discoveries
Geologists have
discovered that
some magmas
had split into two
separate liquids, one
of which is very rich
in iron. Their findings
can help to discover
new iron ore
deposits for mining,
writes Katrien Bollen.
[6] MINING MIRROR JUNE 2018
I
ron ore is mined in about 50
countries. Australia, Brazil, and
China are currently the largest
producers. Iron ore is mostly used
to produce the steel objects that are
all around us — from paper clips to
kitchen appliances and the supporting
beams in skyscrapers. Most iron ore
deposits are found in sedimentary
rocks. Others are mined in volcanic
complexes such as El Laco in Chile
and Kiruna in Sweden. These iron ore
deposits, called Kiruna-type deposits,
account for about 10% of the global
production of iron; yet, nobody knows
how they are formed.
In Nature Communications, a
peer-reviewed journal published by
the Nature Publishing Group — an
international team of researchers
from institutions including KU
Leuven (Belgium), Leibniz University
Hannover, and ULiège — recently
presented the first evidence that these
iron ore deposits are formed when
magma splits into two separate liquids.
“Previous studies have always focused
on the texture or the composition
of natural rocks. We were the first
to actually reproduce magmas in
the lab, such as the ones found in
El Laco,” says last author Olivier
Namur from the Department of Earth
and Environmental Sciences at KU
Leuven, Belgium.
“We wanted to reproduce the
conditions found in magma chambers,
where molten rock accumulates
when it cannot rise to the surface
of the Earth. This is also where the
iron ore deposits beneath volcanoes
are formed, so reproducing the
temperature and pressure of the
magma chambers seemed well worth
examining,” adds Namur.
“We produced a mixture of iron-rich
ore samples and typical lavas surrounding
Kiruna-type deposits. This created a bulk
magma composition that we believe exists
in the deep magma chamber beneath
volcanoes. We placed the mixture in
a furnace and raised the temperature
to 1 000–1 040°C. We also increased
the pressure to about 1 000 times the
atmospheric pressure of Earth. These are
the conditions of a magma chamber.