Abstract
<!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:HyphenationZone>14</w:HyphenationZone> <w:PunctuationKerning/> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:Compatibility> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <w:DontGrowAutofit/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--><p class="MsoNormal" style="text-align: justify; line-height: 200%;"><!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:TrackMoves/> <w:TrackFormatting/> <w:HyphenationZone>14</w:HyphenationZone> <w:PunctuationKerning/> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:DoNotPromoteQF/> <w:LidThemeOther>IT</w:LidThemeOther> <w:LidThemeAsian>X-NONE</w:LidThemeAsian> <w:LidThemeComplexScript>X-NONE</w:LidThemeComplexScript> <w:Compatibility> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <w:DontGrowAutofit/> <w:SplitPgBreakAndParaMark/> <w:DontVertAlignCellWithSp/> <w:DontBreakConstrainedForcedTables/> <w:DontVertAlignInTxbx/> <w:Word11KerningPairs/> <w:CachedColBalance/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> <m:mathPr> <m:mathFont m:val="Cambria Math"/> <m:brkBin m:val="before"/> <m:brkBinSub m:val="--"/> <m:smallFrac m:val="off"/> <m:dispDef/> <m:lMargin m:val="0"/> <m:rMargin m:val="0"/> <m:defJc m:val="centerGroup"/> <m:wrapIndent m:val="1440"/> <m:intLim m:val="subSup"/> <m:naryLim m:val="undOvr"/> </m:mathPr></w:WordDocument> </xml><![endif]--></p><p>Herein, we present and discuss the result of 148 measurements of soil CO<span><sub>2</sub></span> flux performed for the first time in Linosa island (Sicily Channel, Italy), a Plio-Pleistocene volcanic complex no longer active but still of interest owing to its location within a seismically active portion of the Sicily Channel rift system. The main purpose of this survey was to assess the occurrence of CO<span><sub>2</sub></span> soil degassing, and compare flux estimations from this island with data of soil degassing from worldwide active volcanic as well as non-volcanic areas. To this aim soil CO<span><sub>2</sub></span> fluxes were measured over a surface of about 4.2 km<span><sup>2</sup></span> covering ~80% of the island. The soil CO<span><sub>2</sub></span> degassing was observed to be mainly concentrated in the eastern part of the island likely due to volcano-tectonic lineaments, the presence of which is in good agreement with the known predominant regional faults system. Then, the collected data were interpreted using sequential Gaussian simulation that allowed estimating the total CO<span><sub>2</sub></span> emissions of the island. Results show low levels of CO<span><sub>2</sub></span> emissions from the soil of the island (~55 ton d<span><sup>-1</sup></span>) compared with CO<span><sub>2</sub></span> emissions of currently active volcanic areas, such as Miyakejima (Japan) and Vulcano (Italy). Results from this study suggest that soil degassing in Linosa is mainly fed by superficial organic activity with a moderate contribution of a deep CO<span><sub>2</sub></span> likely driven by NW-SE trending active tectonic structures in the eastern part of the island.</p>
Highlights
The release of gases such as CO2 from the soil is a common process that occurs in both tectonic and volcano-tectonic areas
Because tectonic lineaments are often buried by soil and/or sediments that act as a gas diffuser, measurements of gas emissions from soil can provide useful information regarding the presence of hidden and/or active faults [Giammanco et al 1997, Ciotoli et al 1998, Lewicki and Brantley 2000, Guerra and Lombardi 2001, De Gregorio et al 2002, Aiuppa et al 2004, Giammanco et al 2006], as well as changes in the in feeding system of active volcanic areas [Giammanco et al 1995, Federico et al 2011, Camarda et al 2012]
This range of fluxes is lower than that observed in active volcanic areas, such as the island of Vulcano and Mount Etna (Italy), where the measured soil CO2 fluxes generally display values up to three orders of magnitude [Chiodini et al 1998, Camarda et al 2012]
Summary
The release of gases such as CO2 from the soil is a common process that occurs in both tectonic and volcano-tectonic areas. Large amounts of CO2 are released from ascending magmas or generated by crystallization of deep magma bodies [Harris and Rose 1996, Camarda et al 2012]. Part of this CO2 is released into the atmosphere through summit craters, while another part is emitted from the soil along the flanks of volcanoes. In non-volcanic environments, moderate to strong emission of CO2 are usually encountered in areas with the occurrence of active tectonic structures, such as faults and fractures, which constitutes highly permeable preferential pathways for natural emissions of deep gases. Few submarine exhalative manifestations were identified near the top of a submerged relict volcanic structure located in the SW offshore of the island [Lanti et al 1988]
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