Magnesite is storing greenhouse gases

Archaea as climate saviours?

10. February 2023 by Hanna Möller
Geologist Jennifer Zwicker from the University of Vienna is studying whether archaea are playing a role in forming magnesite or not, exemplified by the Kraubath magnesite deposit in Styria, Austria. If they are, these tiny microorganisms could help us combat the climate crisis.
Kraubath in Styria is overcast with magnesite, which is recognisable here from its distinctive white veins. Its formation still presents some mystery to research. The mineralogist Jennifer Zwicker from the University of Vienna assumes that tiny bacteria have their share in this and thus contribute to combating climate change. © Jennifer Zwicker

Our Earth is constantly moving: Tectonic forces can swallow an entire sea and spew whole mountains. This will also happen to our Mediterranean Sea in the remote future and this way, approximately 400 million years ago, ancient rocks of the Kraubath deposit in Styria came to life through the formation of the Alps.

In the office at UZA II of the University of Vienna, the geologist Jennifer Zwicker is turning a rock covered by magnesite veins from the Kraubath deposit in her hands. She chipped off the stone with a hammer and sawed it up into individual parts. How exactly the magnesite that is usually of hydrothermal origin comes to the Eastern Alps and whether the underlying mechanisms could help us combat the climate crisis is the subject of the young scientist’s current research project.

Working at Kraubath
The Kraubath magnesite deposit is located in the middle of the Murtal valley, between the Styrian cities of Leoben and Knittelfeld. The geologist Jennifer Zwicker (in the picture) investigates how the local magnesite is forming. Today, in this stone quarry, magnesite is still mined and used commercially. By the way, Austria is among the top ten countries mining the sought-after raw material. © Christian Lengauer

Formation of magnesite at the sea floor

Where the tectonic plates are drifting apart, dissolved material is spilling from the Earth's interior. These so-called spreading zones are often found at the sea floor, says Jennifer Zwicker. If Earth material is rising slowly enough with high temperatures and the chemical composition is appropriate, peridotite is formed. In contact with water, peridotite is converted to serpentine, which is the 'construction material of magnesite'.

Serpentinisation – this is what mineralogists call the process of mineral conversion – is also occurring on shore under low temperatures. "Magnesite is also being formed if ground water is circulating in continental seabed rock. This can happen in very saline lakes or in some alkaline springs, but also in the Kraubath magnesite deposit in Styria," explains the geologist.

The mystery surrounding the magnesite in Styria

Magnesite formation in the Eastern Alps still presents some mystery to research. A relatively recent explanation for it, which is also put forward by Jennifer Zwicker, emphasises the influence of very tiny archaea, i.e. organisms that, in addition to bacteria and eukaryotes, are the third domain of life, "A solution becomes a solid body if the thermodynamic conditions are suitable. But sometimes these are absolutely not suitable and we, nevertheless, find magnesite. On land, rock is serpentinised by rainwater, resulting in the formation of hydrogen, which archaea can use for their metabolism. In this process, archaea are producing energy. As a side product, new solids, such as magnesite can form."

Archaea vs bacteria

Archaea, in addition to bacteria and eukaryotes are forming the third domain of life. They are the only organisms we know of that can produce methane. The main characteristic of archaea, differentiating them from bacteria, is their membrane which is extremely robust. This makes them true survivalists and they feel comfortable even when being exposed to extreme temperatures: in the volcanic landscapes of Iceland, at temperatures above 110 degrees Celsius or, rather moderate, in the garden of the UZA II of the University of Vienna.

Archaea as key organisms

Jennifer Zwicker and her colleagues already found archaea baked as molecular fossils in similar environments in Turkey. For the Kraubath magnesite deposit, they are still looking for the powerful evidence highlighting the key role of archaea in magnesite formation.
To find this evidence, the mineralogists is analysing rock samples from Kraubath on the one hand, and she is cultivating archaea under Kraubath conditions in the laboratory, on the other. As a first step, the researcher has studied the basics of microbiology and had to spend a lot of time in the white lab coat, “As a geologist, I usually focus on inorganic chemistry and physical processes, but the link to microbiology can shed new light on the matter.”

Getting Kraubath rock into the laboratory

In the laboratory, the usually very frugal archaea are becoming extremely demanding. “They need the correct pH value and the perfect temperature range, otherwise, the cultures die,” Jennifer Zwicker explains. With this project, she is approaching the emerging discipline of geomicrobiology for the first time, “This can be quite frustrating sometimes”. Nevertheless, the committed scientist has never thought about giving up because the processes in the close Eastern Alps are “far too exciting”.    

Archaea as climate saviours?

Magnesite deposits are actually a hot topic in geology, not only because magnesite is extremely heat resistant and thus needed as fire-proof material for the production of blast furnaces and similar products. Magnesite (MgCO3) largely consists of carbon and its deposits are at a premium as storage site for carbon dioxide. The greenhouse gas from the atmosphere is thus rendered harmless as a solid. And if archaea are actually responsible for this, these microorganisms can also be used for the protection of the climate in the long term. However, before they can be used in an industrial process, several questions need to be answered. Nevertheless, Jennifer Zwicker is leaving no (magnesite) stone unturned in her basic research which provides the basis for future research on this issue. (hm)

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Jennifer Zwicker is investigating how magnesite is forming under temperatures below 80 degrees at the Department of Mineralogy and Crystallography. Together with national and international research groups in the fields of mineralogy, geochemistry and microbiology, she wants to answer the question whether methanogenic archaea are contributing to this. The Hertha Firnberg fellow funded by the Austrian Science Fund is not only going to the Kraubath magnesite deposit for research purposes, but she also likes to spend time climbing in the mountains.