Publication Date:
2017-04-04
Description:
Abstract—The marine sector surrounding Panarea Island (Aeolian Islands, South Italy) is affected by
widespread submarine emissions of CO2 -rich gases and thermal water discharges which have been known
since the Roman Age. On November 3rd, 2002 an anomalous degassing event affected the area, probably in
response to a submarine explosion. The concentrations of minor reactive gases (CO, CH4 and H2) of
samples collected in November and December, 2002 show drastic compositional changes when compared
to previous samples collected from the same area in the 1980s. In particular the samples collected after the
November 3rd phenomenon display relative increases in H2 and CO and a strong decrease in the CH4
contents, while other gas species show no significant change. The interaction of the original gas with
seawater explains the variable contents of CO2, H2S, N2, Ar and He which characterize the different
samples, but cannot explain the large variations of CO, CH4 and H2 which are instead compatible with
changes in the redox, temperature and pressure conditions of the system. Two models, both implying an
increasing input of magmatic fluids are compatible with the observed variations of minor reactive species.
In the first one, the input of magmatic fluids drives the hydrothermal system towards atypical (more
oxidizing) redox conditions, slowly pressurizing the system up to a critical state. In the second one, the
hydrothermal system is flashed by the rising high-T volcanic fluid, suddenly released by a magmatic body
at depth. The two models have different implications for volcanic surveillance and risk assessment: In the
first case, the November 3rd event may represent both the culmination of a relatively slow process which
caused the overpressurization of the hydrothermal system and the beginning of a new phase of quiescence.
The possible evolution of the second model is unforeseeable because it is mainly related to the thermal,
baric and compositional state of the deep magmatic system that is poorly known.
Description:
Published
Description:
reserved
Keywords:
NONE
;
03. Hydrosphere::03.04. Chemical and biological::03.04.06. Hydrothermal systems
;
04. Solid Earth::04.02. Exploration geophysics::04.02.01. Geochemical exploration
;
04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
Format:
435100 bytes
Format:
application/pdf
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