| Title | Geothermal potential of Mount Etna region, eastern Sicily. |
|---|---|
| Authors | Branca, Copat, Giammanco, La Delfa, Lentini, Motta, Salerno |
| Year | 2013 |
| Conference | European Geothermal Conference |
| Keywords | Mt. Etna, geothermal energy, geology, geochemistry of fluids |
| Abstract | Mt. Etna is a composite basaltic stratovolcano covering a surface of 1200 km2 in eastern Sicily; with a maximum diameter of about 45 km. Structurally, Mt. Etna is located between the Gela-Catania foredeep and the frontal wedge of the allochthonous Apenninic- Maghrebian thrust-system. This chain-system tectonically overlies a deep seated thrust-system, originated since late-Miocene, by deformation of the old Hyblean Foreland margin (African continental plate Foreland). Recent stratigraphic data of the new geological map of Mt. Etna indicate a complex succession forming the volcano edifice, composed mainly by lava successions consisting of an alternation of massive, scoriaceous and autoclastic lavas characterized by high permeability with several typologies of interlayered volcaniclastic deposits. The whole sequence of volcanic products rests on a sedimentary basement mainly formed by clays and marly clays belonging both to the different tectonic units of the Apenninic-Maghrebian chain and the Quaternary foredeep succession. This structural setting of Mt. Etna region together with the high permeability of volcanic products favours the development of various hydro-structures extended from the top of the volcano to its periphery according to three main sectors located in the north, west and east flanks. For these reasons, the volcano edifice is one of the largest aquifer system and the main water resource in Sicily. Geothermal manifestations at Mt. Etna and in its surrounding area are well known and earlier attempts to exploit geothermal energy date back to 1930’s. The most prominent geothermal manifestations in the Mt. Etna area, is the so-called Salinelle of Paternò mud volcanoes system (located in the lower south-western flank of Etna), which fluid emissions can reach temperature up to 48 °C. Between the water springs, only one is considered as a hypothermal emission (Santa Venera spring), though some water wells have revealed water with temperature of about 35 °C. Other indications of geothermal manifestation at Mt. Etna are indirectly suggested from hydro-geochemical surveys. Gaswater- rock interaction is particularly effective where deep faults cut the volcanic edifice down to the magma reservoirs and allow for an easier escape of magmatic volatiles to the surface. Examples can be found in the south-western and eastern flanks of Mt. Etna, where groundwater displays a significantly higher salinity as a result of higher contents of most of the elements leached from host rocks and higher values of dissolved CO2. Changes in the chemical and physico-chemical characteristics of Mt. Etna’s groundwaters are related, either directly or indirectly, to input of magmatic fluids (mostly water vapour and CO2) to the aquifers due to the volcanic activity. Increased interaction between hot magmatic fluids and groundwater could also induce or intensify hydrothermalism at least in some parts of Etna’s aquifers. Elements like Cr, Zn and Cu can be tracers of such conditions. Recent studies showed that hipersaline waters discharged by the Salinelle of Paternò are fed by a hydrothermal system whose temperature was estimated at 100-150 °C. |