Publication Date:
2017-04-04
Description:
In November 2007 we conducted a water column and seafloor mapping study of the
submarine volcanoes of the Aeolian Arc in the southern Tyrrhenian Sea aboard the R/V
Urania. On 26 conductivity‐temperature‐depth casts and tows we measured temperature,
conductivity, pressure, and light scattering and also collected discrete samples for helium
isotopes, methane, and pH. The 3He/4He isotope ratio, an unambiguous indicator of
hydrothermal input, showed a clear excess above background at 6 of the 10 submarine
volcanoes surveyed. Marsili seamount had the highest anomaly, where the 3He/4He ratio
reached a d3He value of 23% at 610 m depth compared with background values of ∼5%.
Smaller but distinct d3He anomalies occurred over Palinuro, Enarete, Eolo, Sisifo, and Secca
del Capo. Although hydrothermal emissions are known to occur offshore of some Aeolian
subaerial volcanoes, and hydrothermal deposits have been sampled throughout the arc,
our results are the first to confirm active discharge on Marsili, Enarete, Eolo, Sisifo, and
Secca del Capo. Samples collected over Lametini, Filicudi North, Alicudi North, and
Alcione had d3He near the regional background values, suggesting either absence of, or very
weak, hydrothermal activity on these seamounts. Hydrocasts between the volcanoes
revealed a consistent d3He maximum between 11% and 13% at 2000mdepth throughout the
SE Tyrrhenian Sea. The volcanoes of the Aeolian arc and the Marsili back arc, all 〈1000 m
deep, cannot contribute directly to this maximum. This deep 3He excess may be a remnant
of tritium decay or may have been produced by an unknown deep hydrothermal source.
Description:
Published
Description:
B02102
Description:
1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
Description:
JCR Journal
Description:
reserved
Keywords:
hydrothermal systems
;
helium
;
Tyrrhenian sea
;
seamounts
;
03. Hydrosphere::03.04. Chemical and biological::03.04.06. Hydrothermal systems
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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