Mount Etna's exceptional CO2 emissions are triggered by deep carbon
dioxide reservoirs

Date:
January 20, 2022
Source:
University of Cologne
Summary:
Magma transports carbon dioxide stored in the Earth's mantle to
volcanoes, where it is released into the atmosphere. A research
team now presents results obtained using a new methodology to
clarify the contribution of volcanoes to natural CO2 emissions.



FULL STORY ==========================================================================
The transport of carbon dioxide stored in the Earth's lithospheric mantle beneath the Hyblean Plateau in southern Italy at a depth of approximately
50 to 150 kilometres is responsible for the exceptionally large CO2
emission of Mount Etna. That is the result of research conducted by
an international team of geologists, including researchers from the Universities of Florence (Italy) and Cologne (Germany), and from the
Istituto di Geologia Ambientale e Geoingegneria of the Italian National Research Council (CNR). To reach this conclusion, the team determined
the ratios of a particular set of elements in the magmas emitted by the volcanoes using cutting-edge, high-precision measurement methods. The
results have been published in the article 'A carbon-rich lithospheric
mantle as a source for the large CO2 emissions of Etna volcano (Italy)'
in the journal Geology.


==========================================================================
Over the geological times, variations in atmospheric CO2 depended mainly
on volcanic emissions, which are difficult to estimate because they are
not directly related to the volume of the magmas erupted. Indeed, some volcanoes show exceptionally large emission of CO2 when compared to the
amount that can be dissolved in their magmas. Etna is perhaps the most
striking example, contributing to 10 per cent (9000 tons/day) of the
present global volcanic CO2 emission. That is three times more CO2 than
a volcano like Kilauea (Hawaii) emits, which erupts four times more magma.

The team investigated magmas from four volcanoes in the region (Etna,
Vulture, Stromboli, and Pantelleria), using the two rare elements Niobium
(Nb) and Tantalum (Ta) as tracers. Ratios of Nb/Ta are very constant in
many rocks and are only modified by few geological processes -- like
the infiltration of carbonate-rich melts in Earth's mantle. The study
revealed that magmas from Mount Etna and Mount Vulture are characterized
by extremely high Nb/Ta ratios, higher than any other active intraplate volcano. This means that the magma compositions testify to the presence
of lithospheric mantle domains beneath southern Italy that are extremely enriched in carbon. This carbon is 'tapped' during the melting of
the magmas.

The process is directly related to the region's complex geodynamic
setting: The carbon-rich lithospheric mantle domains are located beneath
the Hyblean Plateau in southern Sicily. These domains are transported
towards the region beneath Etna by means of tectonic activity,
specifically the rollback of the Ionian subduction plate. A symmetric
mechanism is likely occurring on the other side of the Ionian plate,
beneath Mount Vulture.

'The data also allow us to infer the contribution of such carbon-rich
domains to the Earth's atmosphere in the past, suggesting that the CO2 emissions of Mount Etna during its ancient activity might have been even
higher than at present', Professor Dr Carsten Mu"nker from the University
of Cologne's Institute of Geology and Mineralogy commented. He and his
team were responsible for the high precision measurements including the
two critical elements Nb and Ta.

Lead author Dr Alessandro Bragagni, former postdoc at Cologne and now
at the University of Florence, added: 'Similar carbon-rich domains might
be hidden beneath other volcanoes worldwide, hence contributing to their
CO2 emissions.

The innovative trace element approach used in this
study represents a promising way to better estimate the
contribution of carbon-enriched lithosphere to overall
volcanic CO2emissions, both at present and in the past, which
may have played a key role in changing the climate of our planet.' ========================================================================== Story Source: Materials provided by University_of_Cologne. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Alessandro Bragagni, Filippo Mastroianni, Carsten Mu"nker, Sandro
Conticelli, Riccardo Avanzinelli. A carbon-rich lithospheric
mantle as a source for the large CO2 emissions of Etna volcano
(Italy). Geology, 2022; DOI: 10.1130/G49510.1 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220120103353.htm

--- up 6 weeks, 5 days, 7 hours, 13 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)