Publication Date:
2017-04-04
Description:
We have developed two new quantitative approaches to
calculate temperatures in hydrothermal reservoirs by using the
CO2-CH4-CO-H2 gaseous system and to model selective
dissolution of CO2-H2S-N2-CH4-He-Ne mixtures in fresh
and/or air saturated seawater. The anomalous outgassing
starting November 2003 from the submarine exhalative
system offshore Panarea island (Italy), was the occasion to
apply such approaches to the extensive collection of volcanic
gases.
Gas geothermometry suggest the presence of a deep
geothermal system at temperature up to 350°C and about 12
mol% CO2 in the vapor, which feeds the submarine emissions.
Based on the fractional dissolution model, the rising
geothermal vapor interacts with air-saturated seawater at low
depths, dissolving 30-40% CO2 and even more H2S,
modifying the pH of the aqueous solution and stripping the
dissolved atmospheric volatiles (N2, Ne). Interaction of the
liquid phase of the thermal fluids with country rocks, as well
extensive mixing with seawater, have been also recognized
and quantified.
The measured output of hydrothermal fluids from Panarea
exhalative field [1] accounts for the involvement of volatiles
from an active degassing magma, nonetheless the climax of
the investigated phenomenon is probably overcome and the
system is new tending towards a steady-state. Our quantitative
approaches allow us to monitor the geochemical indicators of
the geothermal physico-chemical conditions and their
potential evolution towards phreatic events or massive gas
releases, which certainly are the main hazards to be expected
in the area. The event at Panarea has in fact highlighted how
hydrothermal systems can exhibit dramatic and sudden
changes of their physico-chemical conditions and rate of fluid
release, as a response to variable activity of feeding magmatic
systems.
Description:
Published
Description:
Copenhagen
Description:
1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
Description:
open
Keywords:
Submarine
;
geochemistry
;
04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
Extended abstract
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