Hydrothermal circulation on Ischia Island (Southern Italy), revealed by an integrated geochemical, geophysical and geological approach

Volcano-hosted hydrothermal systems are complex geological objects, whose thorough characterisation requires extensive and interdisciplinary work. Indeed, even thought geological, geochemical and geophysical observations offer highly significant but independent information, only an integrated multidisciplinary approach can yield a comprehensive characterisation of the chemical/physical structure of hydrothermal systems. Notwithstanding the extensive application of geological, geochemical and geophysical techniques in geothermal research, there are only a few examples in the literature of concurrent use of the three techniques [Finizola et al., 2002; Zlotnicki et al., 2009]; these studies ov…

The Ischia Island hydrothermal system: an integrated multidisciplinary (geochemical, geophysical and geological) study

Ischia Island is the emergent portion of a large volcanic complex on the Gulf of Naples (Southern Italy). Ischia volcano has undertaken a complex evolution since 150 ka b.p., with prolonged cycles of effusive and explosive eruptions alternated with quiescence periods (the most recent of which started after the 1302 A.D. Arso eruption). Currently, hot springs (with discharge temperature up to 90 C), fumarolic gas emissions with CO2 up to 97%, and diffuse soil degassing testify a persistent activity state of the Ischia volcano. Ischia Island is a very good example of an active volcano hosting a large hydrothermal system and, in particular, its south-western sector has long been known to be th…

CO2 vents areas show effects of ocean acidification on benthic rocky shores assemblages

The flight of Arcadia: spatial CO2/SO2 variations in a cross section above the Nord East crater of Etna volcano

The CO2/SO2 ratio in volcanic plumes of open conduit volcanoes can provide useful information about the magma depth inside a conduit and the possible occurrence of an eruptive event. Moreover, the same CO2 measurement when combined with a SO2 flux measurement, commonly carried out at many volcanoes nowadays, is used to contribute to an improved estimate of global volcanic CO2 budget. Today worldwide at 13 volcanoes automated in-situ instruments (known as Multi-GAS stations) are applied to continuously determine CO2/SO2 ratios and to use this signal as additional parameter for volcanic monitoring. Usually these instruments carry out measurements of half an hour 4 – 6 times/day and thus provi…

Pizzi Deneri Field Trips - Etna 2010-2014

The structure of a hydrothermal system from an integrated geochemical, geophysical and geological approach: the Ischia Island case study

The complexity of volcano-hosted hydrothermal systems is such that thorough characterisation requires extensive and interdisciplinary work. We use here an integrated multidisciplinary approach, combining geological investigations with hydrogeochemical and soil degassing prospecting, and resistivity surveys, to provide a comprehensive characterisation of the shallow structure of the south-western Ischia’s hydrothermal system. We show that the investigated area is characterised by a structural setting that, although very complex, can be schematised in three sectors, namely the extra caldera sector (ECS), caldera floor sector (CFS), and resurgent caldera sector (RCS). This contrasted structura…

Atmospheric CFCs and geogenic HCFCs in gas discharges from Mt Etna and Vulcano Island (Italy)