Journal of Volcanology and Geothermal Research 253 (2013) 65–74

Contents lists available at SciVerse ScienceDirect

Journal of Volcanology and Geothermal Research

j ourna l homepage: www.e lsev ie r .com/ locate / jvo lgeores

Active degassing of mantle-derived fluid: A geochemical study along the Vulture line,southern Apennines (Italy)

A. Caracausi a, M. Martelli a, P.M. Nuccio a, M. Paternoster b,⁎, F.M. Stuart c

a Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Palermo, Via Ugo La Malfa 153, 90146 Palermo, Italyb Dipartimento di Scienze,Universita'della Basilicata, Campus Macchia Romana, 85100 Potenza, Italyc Isotope Geosciences Unit, Scottish Universities Environmental Research Centre, East Kilbride G75 0QF, UK

⁎ Corresponding author. Tel.: +39 971 205832; fax: +E-mail address: micpaternoster@yahoo.it (M. Patern

0377-0273/$ – see front matter. Published by Elsevier Bhttp://dx.doi.org/10.1016/j.jvolgeores.2012.12.005

a b s t r a c t

a r t i c l e i n f o

Article history:Received 10 August 2012Accepted 11 December 2012Available online 20 December 2012

Keywords:Southern ApenninesVulture lineHelium and carbon isotopesGas emissions

We report the results of a geochemical study of gas emissions along a NE–SW transect in southern Italy in orderto test the hypothesis that the region around Monte Vulture is affected by degassing of mantle-derived fluidsthrough a lithospheric discontinuity. We also investigated lavas from the Monte Vulture volcano displaying3He/4He (up to ~6.0 Ra) and Sr isotopes that are consistent with an origin inmantle that has hadminimal pollu-tion from subducted Adriatic slab. Similar 3He/4He in fluids from around Mt. Vulture indicate that the deep vol-canic system is still degassing.Mantle-derivedHe occurs in fluids along the length of the Vulture line, reinforcingthe hypothesis that it is a deep tectonic discontinuity along which mantle fluids and/or melts advect to the sur-face. The CO2/

3He ratios are highly variable (2.7×108–2.15×1011) in response to processes such as gas dissolu-tion into aquifers, addition of crustal gases and degassing fractionation.

Published by Elsevier B.V.

1. Introduction

Monte Vulture is the eastern-most occurrence of the QuaternaryItalian volcanism, and is the only volcano to the east of the Apenninemountain belt. It has peculiar petrologic characteristics, not least thetrace element pattern and isotopic features that are intermediate be-tween intraplate and subduction-related signatures (e.g. Beccaluvaet al., 2002; Peccerillo, 2005; De Astis et al., 2006). These featureshave stimulated an intense debate about its origin and significance(D'Orazio et al., 2007, 2008; Stoppa et al., 2008). The origin of the volca-nism has been ascribed to a NE–SW trending lithospheric discontinuitythat was generated by variation in the velocity of subduction rollbackalong the length of the subducting plate that has generated a verticalslab window (i.e., Doglioni et al., 1994; Govers and Wortel, 2005;D'Orazio et al., 2007). The detection of mantle-derived fluids along theVulture line constitutes a method of verifying the hypothesis. The 3He/4He ratio of themantle is approximately three orders ofmagnitude higherthan helium produced in the continental crustal source and is an unam-biguous tracer of a mantle degassing in crustal fluids (e.g., O'Nions andOxburgh, 1988). Given that active faults are the preferential conduit fortransferring deep fluids to the surface (e.g. King, 1986), the study ofhelium isotopes has beenwidely used to trace deep faults andmake infer-ences about the characteristics of the deep-degassing bodies (magmasand/or mantle; Kennedy et al., 1997; Güleç et al., 2002; Kulongoskiet al., 2003; Pik and Marty, 2009; Umeda and Ninomiya, 2009). In addi-tion, helium isotopic composition of melt/fluid inclusions trapped into

39 971 205678.oster).

.V.

olivine and pyroxene phenocrysts frommafic lavas or xenoliths can pro-vide useful information on source mantle (e.g. Hilton et al., 2002). In thispaper, we report the chemical and isotopic composition of gas emissionsand springwaters collected along aNE–SWtransect through the southernAppennines in order to quantify the contribution of mantle-derivedhelium in crustal fluids and consequently to evaluate the existence of astructural discontinuity (the “Vulture line”). We use new He and Sr iso-tope data of Monte Vulture lavas to place constraints on themantle com-position and compare He data between fluids and lavas.

2. Geodynamical and volcanological framework

The southern Apennines are a roughly NW–SE oriented segment of afold-and-thrust belt that belongs to the complex geodynamic settingcharacterizing the centralMediterranean. Since the Tortonian, the thrustfront hasmigrated to the southeast due to the rollback of a west dippingslab and the back-arc basin opening to west (Malinverno and Ryan,1986). Since the middle Pleistocene, the Apennine foreland has showntwo distinct structural domains, the central Adriatic region and the Apu-lian region (Doglioni et al., 1994; references within). Both the geometryand the kinematics of the accretionary wedge and the related forelandhave evolved differentially. These differences are interpreted as due tovariation in the rate of hinge rollbackbetween the northern Adriatic lith-osphere (110 km thick) and the southern Apulian lithosphere (70 kmthick). The different lithospheric thicknesses appear to have controlledthe variable degree of flexure of the lithosphere itself, the asthenospher-ic penetration rate and the formation of lithospheric transfer zone.Furthermore, the increasing length of the Apennine arc, due to the east-ward rollback of the subduction hinge, may control the development of

66 A. Caracausi et al. / Journal of Volcanology and Geothermal Research 253 (2013) 65–74

“comb” grabens which are oriented perpendicular to the arc (Doglioniet al., 1994), as the E–W trending Ofanto graben, located to the southof Gargano promontory. While compression is confined to the foreland,the inner and axial sectors of the Apennines are characterized by a NE–SW striking extension (Frepoli and Amato, 2000; Pondrelli et al., 2002;Frepoli et al., 2005), associated with uplift, volcanism, and high fluxesof heat and CO2 (Bartolini et al., 2003; Chiodini et al., 2004; Montoneet al., 2004). This widespread extension is responsible for the NW–SEstriking Apennine faults that affect the Apennine axial zone and boundthe main intermountain basins.

Seismic tomography supports the presence of a subducting Apen-nine slab (e.g. Piromallo and Morelli, 2003), in particular, alongsouthern Apennines Doglioni et al. (1999, 2007) propose the pres-ence of vertical slab window. Rosenbaum et al. (2008) show gapswithin the subducting lithosphere beneath Italy, which have beeninterpreted as deep (100–500 km) sub-vertical tear faults generatedby different rates of subduction rollback of the narrow slab segment(Govers and Wortel, 2005; Schellart et al., 2007). A possible linkbetween the development of vertical tear faults and the occurrenceof regional magmatism has been proposed by Rosenbaum et al.(2008). The lithospheric tears accommodated strike-slip displacementsduring slab tearing propagation. The crustal expression of such faults ispossibly related to the existence of orogen-perpendicular strike-slipfaults within the Apennine fold-and-thrust belt (e.g. Di Luccio et al.,2005; Schiattarella et al., 2005; Billi et al., 2006; Scrocca, 2006). TheVulture line (Fig. 1) is interpreted as N40°–50° trending deep fault,cutting the entire chain-foreland system (Schiattarella et al., 2005).

In this geodynamic setting Mt. Vulture is the most striking exam-ple of an asthenospheric upwelling along slab tears faults (D'Orazioet al., 2007; Rosenbaum et al., 2008). Volcanic activity started at

Fig. 1.Map showing the interrelation between: A) simplified geological map of the southern(an expression of the N 40–50° system fault that cutting the entire chain-foreland system, mthe Fig. 7, and sampling sites; B) vertical slab windows inferred beneath the Southern Ape(from Scrocca et al., 2005, modified).

742±11 kyr and continued until 142±11 kyr, interrupted by sever-al long inter-eruptive periods (Büettner et al., 2006, and referencestherein). The volcanism is strongly silica undersaturated, from alka-line potassic to ultrapotassic affinities (De Fino et al., 1982, 1986).Giannandrea et al. (2006) have grouped the volcanic units in twodistinct super-synthems: 1) Mt. Vulture and 2) Monticchio phases.The Mt. Vulture units are the oldest volcanic products and are repre-sented by lavas and pyroclastic deposits that range in compositionfrom basanite–foidite to phonolite. The Monticchio units are prod-ucts of the most recent eruptions. They produced some maar-typevents with tuff aprons and have a carbonatitic–melilititic composi-tion (Stoppa and Principe, 1997). The primary origin of the carbonatefraction is currently being debated (see D'Orazio et al., 2007, 2008;Stoppa et al., 2008).

3. Sampling and analytical procedures

3.1. Volcanic rocks

Volcanic rocks of different ages from the Mt. Vulture complex weresampled with the aim of determining the helium and strontium isotopecomposition of local mantle. Fresh olivine and/or pyroxene phenocryst-bearing basaltic lavas or pyroclastic deposits were sampled. Sampleswere selected on the basis of (i) availability of olivine and/or pyroxenephenocrysts, and (ii) rock composition (low SiO2 and high Mg content,high concentration of compatible elements (e.g. Ni and Cr)) in order toavoid crustal contamination. In particular, we focused our attention onthe last eruption (~140,000 years ago), that formedmaar craters belong-ing to theMonticchio super-synthems (Giannandrea et al., 2006). Detailsof sample location and rock and synthem type are given in Table 1.

Appenines (from Bentivenga et al., 2004, modified) with the location of the Vulture Lineodified by Schiattarella et al., 2005), CROPO4 deep seismic reflection profile, profile of

nnines (from D'Orazio et al., 2008, modified); and C) regional geological cross-section

Table 1General data and helium and strontium isotope analyses of the studied rock samples.

Sample LocationN

LocationE

Alt. m.(a.s.l.)

Type Synthem SubSynthem Age(reference)

Phase Weight(g)

3He/4He(R/Ra)

[He](10−8 cm3 STP/g)

87Sr/86Sr

P2 40° 55 951 15° 40 376 670 Pyroclastic Surge Barile Rionero 672±6 ka(Büettner et al., 2006)

cpx 4.68 4.48±0.03 22.43±0.01 0.705570±19cpx

P2 40° 55 951 15° 40 376 670 Pyroclastic Surge Barile Rionero 672±6 ka(Büettner et al., 2006)

ol 5.42 5.18±0.34 0.32±0.01

P4 40° 57 346 15° 40 492 550 Pyroclastic Flow Barile Vulture–San Michele 601±7 ka(Brocchini et al., 1994)

cpx 4.49 4.34±0.04 12.38±0.01 0.705885±13cpx

P4 40° 57 346 15° 40 492 550 Pyroclastic Flow Barile Vulture–San Michele 601±7 ka(Brocchini et al., 1994)

ol 5.48 5.31±0.30 0.52±0.01

V2 40° 57 346 15° 40 492 550 Lava flow Barile Vulture–San Michele 601±7 ka(Brocchini et al., 1994)

ol 4.75 4.63±0.36 0.95±0.01

V4 40° 57 752 15° 34 511 505 Lava flow Barile Vulture–San Michele 601±7 ka(Brocchini et al., 1994)

ol 5.14 5.06±0.13 3.45±0.01 0.705264±13wr

V4 40° 57 752 15° 34 511 505 Lava flow Barile Vulture–San Michele 601±7 ka(Brocchini et al., 1994)

cpx 4.59 4.45±0.04 23.93±0.01

V5 40° 55 865 15° 39 254 500 Scoriae Valle dei Grigi-Fosso del corbo Case lopes 484±8 ka(Brocchini et al., 1994)

ol 5.93 5.77±0.32 0.01±0.01

P5 40° 55 865 15° 39 254 500 Pyroclastic Surge Valle dei Grigi-Fosso del corbo Case lopes 484±8 ka(Brocchini et al., 1994)

ol 5.64 5.47±0.46 0.47±0.01

P5 40° 55 865 15° 39 254 500 Pyroclastic Surge Valle dei Grigi-Fosso del corbo Case lopes 484±8 ka(Brocchini et al., 1994)

cpx 4.70 4.47±0.06 10.29±0.01 0.705854±14cpx

V6 40° 56 985 15° 69 385 720 Bombs Laghi di Monticchio Lago Grande 130–140 ka(Büettner et al., 2006)

ol 5.05 4.87±0.10 1.54±0.01

V6 40° 56 985 15° 69 385 720 Bombs Laghi di Monticchio Lago Grande 130–140 ka(Büettner et al., 2006)

cpx 4.13 3.99±0.05 3.02±0.01

V7 40° 56 985 15° 69 385 720 Bombs Laghi di Monticchio Lago Grande 130–140 ka(Büettner et al., 2006)

cpx 4.00 3.88±0.09 5.82±0.01

V7 40° 56 985 15° 69 385 720 Bombs Laghi di Monticchio Lago Grande 130–140 ka(Büettner et al., 2006)

ol 4.57 4.43±0.28 0.53±0.01

P6 40° 56 162 15° 35 519 700 Ash flow Laghi di Monticchio Lago Grande 130–140 ka(Büettner et al., 2006)

cpx 6.13 6.06±0.03 290±0.07 0.705648±19cpx

P6 40° 56 162 15° 35 519 700 Ash flow Laghi di Monticchio Lago Grande 130–140 ka(Büettner et al., 2006)

ol 6.31 6.02±0.03 22.50±0.01

V9 40° 56 162 15° 35 519 700 Tuffisitic lapilli Laghi di Monticchio Lago Piccolo 132±12 ka(Brocchini et al., 1994)

cpx 5.38 5.66±0.10 2.50±0.01

V9 40° 56 162 15° 35 519 700 Tuffisitic lapilli Laghi di Monticchio Lago Piccolo 132±12 ka(Brocchini et al., 1994)

ol 6.24 5.65±0.27 0.27±0.01

V10 40° 56 162 15° 35 519 700 Spinel lherzolites Laghi di Monticchio Lago Piccolo 132±12 ka(Brocchini et al., 1994)

ol 6.12 6.03±0.07 4.50±0.01 0.704258±16wr

Notes: The 3He/4He isotope ratio is expressed as R/Ra, where R=(3He/4He) sample and Ra=(3He/4He)atm=1.39E−6. Helium concentrations are calculated using the weight of sample that was crushed to less than 0.5 mm. The 87Sr/86Srratios have been measured in cpx (pyroxenes) or wr (whole rock). P6 data reported also by Martelli et al. (2008).

67A.Caracausiet

al./JournalofV

olcanologyand

Geotherm

alResearch253

(2013)65

–74

68 A. Caracausi et al. / Journal of Volcanology and Geothermal Research 253 (2013) 65–74

Samples P6 and V9 were collected from a surge deposit of theMonticchio lakes synthem associated with the formation of two clas-sic maar craters (Stoppa and Principe, 1997). These units containpeculiar tuffisitic lapilli that displaying a concentric-structure coredwith megacrysts or ultramafic nodules (V9 sample) that originatefrom the lithospheric mantle at 50–70 km (Jones et al., 2000; Downeset al., 2002). Surge deposit of the Monticchio lakes synthem is com-posed of a fine ash matrix (sample P6) containing peridotite nod-ules (sample V10) and xenocrysts (olivine, emerald-green pyroxene,black amphibole, mica and spinel fragments). The depositional textures(such as the concentric-structured lapilli) suggest that magma ascentwas very rapid (Stoppa and Woolley, 1997).

The strontium isotope analyses were performed on whole rock ba-salts and on clinopyroxenes from pyroclastic deposits, using a VG 54Ethermal ionization mass spectrometer at SUERC (East Kilbride, UK)and following the procedures of Martelli et al. (2004). Helium isotopeswere measured in gases released by single-step, in vacuo crushing ofolivine and pyroxene phenocrysts and xenoliths using a MAP 215-50mass spectrometer at SUERC. Analytical procedures are similar tothose of Stuart et al. (2000). The hydraulic crusher used in this studydoes not release lattice-hosted radiogenic (Stuart et al., 2003) or cosmo-genic He (Williams et al., 2005).

3.2. Fluids

Gas emissions and spring waters (Tito and Pozzo Fore) were col-lected from a NE to SW transect in the southern Apennines, alongthe trace of the Vulture line (Fig. 1). Water samples were selectedon the basis of their peculiar hydrogeochemical features and distribu-tion in the territory in relation to the tectonic framework. Among thestudied emissions, S. Cataldo, Paestum andMt. Vulture springs are gasbubbling in water, S. Sisto, Contursi, and Maschito are dry mofettes,while Tito and Fore are water springs without a free gas phase. Gas-eous samples were collected in pyrex bottles with vacuum valves atboth ends, taking care to prevent air contamination.

We analyzed the chemical (O2, N2, CH4, He, and CO2) and isotopic(3He/4He, δ13CCO2) compositions of free gases and gases dissolvedin water. Chemical and isotopic analyses of fluids were performedat Istituto Nazionale di Geofisica e Vulcanologia (INGV—Palermo).Dissolved and free gases were analyzed by double detector (TCD-FID)Perkin Elmer Autosystem XL gas chromatograph using Ar as carriergas and a 4 m Carboxen 1000 column. Dissolved gases in the Fore andTito samples were analyzed according to the method proposed byCapasso and Inguaggiato (1998). The chemical and isotopic (δ13CCO2and 3He/4He) analyses are reported in Table 2.

The 3He/4He were measured in a split-flight-tube mass spectrom-eter (GVI Helix SFT). Ion beams of 3He and 4He were simultaneouslydetected by a double collector system that yielded isotopic ratio preci-sion within ±0.5%. Purified atmospheric heliumwas used as a runningstandard. 4He/20Ne ratiosweremeasuredwith a quadrupolemass spec-trometer. The carbon isotope composition of carbon dioxide was mea-sured by using a Thermo Delta XP IRMS (analytical error is ±0.15‰)coupled with TRACE GC gas-chromatograph, separated using a 30 mQ-plot column (i.d. 0.32 mm). δ13C values are per mil vs. V-PDB.

4. Result and discussion

4.1. Helium isotopes in phenocrysts

The 3He/4He ratio of olivine and pyroxene phenocrysts is the bestway to characterize the mantle composition and the processes duringmagma transport and residence in the crust (degassing events, crustalcontamination, mixing processes, etc.). We have analyzed olivine andclinopyroxene phenocrysts from nineteen rock samples from theMt. Vulture volcanic complex from 670 to 132 kyr (Table 1).

The 3He/4He of clinopyroxene (3.88 to 6.03 Ra) is usually slightlylower than cogenetic olivine (4.43 to 6.03 Ra) (Fig. 2). This is typicalof Italian Quaternary volcanic rocks from Mt. Etna, the Roman prov-ince and Aeolian islands (Marty et al., 1994; Martelli et al., 2004,2008; Nuccio et al., 2008; Coulson et al., 2011) and likely reflects dif-fusive loss through clinopyroxene at magma temperatures (Trull andKurz, 1993) and crustal contamination (Shaw et al., 2006). Olivinespreserve helium isotope compositions that are best representativeof the mantle value.

Samples P6 and V9 display isotopic equilibrium between olivineand clinopyroxene (3He/4He=5.5–6.0 Ra), suggesting that thesesamples probably mirror the pristine magmatic value. Xenolithic ol-ivine (sample V10) also has 3He/4He of 6.0 Ra (Table 1). The 87Sr/86Srof V10 (0.7042) overlaps the range of values measured previouslyin xenoliths (Downes et al., 2002). The lavas and pyroclastic rockshave 87Sr/86Sr in the range of 0.7052 to 0.7058. These are similar topreviously measured in Mt. Vulture lavas (De Astis et al., 2006, andreferences therein). Samples P6, V9 and V10 can be considered themost representative samples of lithospheric mantle beneath Mt. Vul-ture, and we assume 3He/4He~6 Ra and 87Sr/86Sr=0.7042. Thelower 3He/4He of olivine from samples V4, V6, V7 (4.5–5 Ra; Fig. 2)is unlikely to be due to post-eruption radiogenic He ingrowth.From a plot of 3He/4He vs He concentration (Fig. 3), it can be seenthat olivine from V5 has 3He/4He ratio that is close to the sampleswith the highest concentration although it has the lowest He concen-tration. The low 3He/4He could be generated by contamination of ahomogeneous 6 Ra mantle source by subtle crustal contamination,or it may reflect mantle heterogeneity. Previous studies on majorand trace elements and Sr isotopes have excluded crustal contamina-tion of Mt. Vulture lavas and there is consensus that the variation re-flects mantle source heterogeneity (Beccaluva et al., 2002; Downeset al., 2002; De Astis et al., 2006; D'Orazio et al., 2007). The ItalianQuaternary volcanic province shows clear correlation of He and Srisotopes that reflects mantle heterogeneity (Poliak and Tolstikin,1979; Parello et al., 2000; Martelli et al., 2008). However, there isno clear He–Sr isotope correlation at Mt. Vulture (Fig. 4) suggestingthat the low 3He/4He may reflect contributions from several sourcesat mantle or crustal level. The similarity of the maximum 3He/4Heover 600 ka of magmatism (Fig. 5) implies that the 3He/4He of Vul-ture lithospheric mantle has been constant over the history of thevolcano, at a value enriched in crustal/radiogenic He with respectto MORB values (7±1 Ra, Farley and Neroda, 1998). This temporalcoherence is also observed at Mt. Etna (Marty et al., 1994; Nuccioet al., 2008; Coulson et al., 2011).

Previous studies highlighted that Vulture mantle source is char-acterized by enrichment of anorogenic alkaline components (Na,High Field Strength and Low Rare Earth elements) subsequently affect-ed by orogenic subduction-related metasomatism (enrichment of LowField Strength elements and marked negative anomalies of Ti andNb, Beccaluva et al., 2002). Such hybrid character is also supportedby isotopic systematic of Sr–Nd–Pb, intermediate between the intra-plate Adriatic mantle and the subduction related-magmas of theItalian peninsula (De Astis et al., 2006; Bianchini et al., 2008). TheMt. Vulture lavas have the highest 3He/4He ratio values (6 Ra) mea-sured in the Italian peninsular magmatism. These values are onlyslightly lower than those of the least contaminated basalts from theSicilian realm (Iblean plateau and Pantelleria; 7.3±0.3 Ra; Parelloet al., 2000; Sapienza et al., 2005; Martelli et al., 2008; Correaleet al., 2012), that are sourced in a mantle unpolluted by metasomaticfluids derived by subduction slab (e.g., Wilson and Bianchini, 1999).Therefore, the new helium isotope data is consistent with the previouspetrology and geochemistry studies that suggest the Mt. Vulture meltsource region is characterized by an intraplate signature with a modestcontribution of a subduction-type component. The anorogenic signa-ture of the pristine mantle (7.3±0.3 Ra) was slightly decreased tothe recorded values (6 Ra) by enrichment of the mantle wedge in 4He

Table 2Chemical and isotopic composition (δ13CCO2 and 3He/4He) of the dissolved and free gases.

No. Sample Geodynamic setting Gas type O2 N2 CH4 CO2 He δ13C(CO2) 4He/20Ne CO2/3He R/Ra (R/Ra)c (R/Ra)ca

1 Paestum (N 40° 26′ 47.15″; E 15° 02′ 47″) Apennines chain Free % vol. % vol. % vol. % vol. ppm ‰ vs. (PDB)March 7, 2006 1.27 86.34 b.d.l. 11.4 174 −9.3 6.1 6.1E+08 0.77 0.75 –

2 Contursi (N 40° 40′ 45.2″; E 15° 15′20.8″) Apennines chain FreeMay 23, 1998 b.d.l. 0.50 0.10 99.5 5.0 −1.5 28 1.05E+11 1.35 1.35 1.35–1.43

3 San Sisto (N 40°42′ 30.5″; E 15°13′ 20.1″) Apennines chain FreeJune 13, 2006 0.12 3.18 0.31 96.5 21.5 0.8 263 2.5E+10 1.27 1.27 1.21–1.37January 18, 2007 b.d.l. 2.49 0.30 98.2 19.3 n.d. 1447 2.8E+10 1.28 1.28April 23, 2007 b.d.l. 2.55 0.31 97.5 17.8 n.d. 1395 2.9E+10 1.33 1.33

4 S. Cataldo (N 40° 45′14.1″; E 15°39′11.5″) Apennines chain FreeJune 12, 2006 0.20 73.1 24.8 1.03 262 −12.5 14.9 2.7E+08 0.10 0.08 0.07–0.09December 19, 2006 0.07 72.9 26.1 1.18 187 n.d. 18.2 4.1E+08 0.11 0.09August 28, 2007 0.14 72.9 24.8 1.10 208 n.d. 19.5 3.8E+08 0.10 0.08

6 Mefite Ansanto (N40°56′25.3″; E15° 09′ 25″)a Apennines chain FreeSeptember 26, 1996 n.d. 1.4 0.2 98.4 9.0 6.0 2.8E+10 2.84 2.77–2.84

7 Mt. Vulture A (N 40°52′18.9″; E 15° 39′ 05″) Apennines chain FreeMay 26, 2003 b.d.l. 0.98 5.7E−04 99.0 1.3 −6.2 16.9 1.3E+11 4.32 4.38March 16, 2004 b.d.l. 1.04 6.0E−04 99.0 1.2 −5.8 10.9 1.3E+11 4.53 4.64

8 Mt. Vulture B (N 40°54′ 53.5″; E 15° 34′ 21.4″) Apennines chain FreeMarch 28, 2002 0.46 1.17 b.d.l. 98.4 1.4 −4.8 6.8 8.8E+10 5.64 5.87May 26, 2003 b.d.l. 1.17 3.5E−04 98.8 2.8 −5.0 37.2 4.4E+10 5.73 5.77

9 Mt. Vulture C (N 40°53′ 25′1″; E 15°40′06.5″) Apennines chain FreeOctober 26, 2001 0.67 2.84 b.d.l. 96.5 2.8 −4.1 7.6 4.1E+10 6.13 6.35

10 Mt. Vulture D (N 40°56′ 50″; E 15°34′18″) Apennines chain FreeMarch 13, 2004 0.2 0.37 4.0E−04 99.4 0.5 −3.2 11.2 2.15E+11 6.13 6.28

11 Maschito (N 40° 54′10.3″; E 15°50′48.5″) Foredeep FreeJuly 28, 2005 0.10 1.91 0.42 97.01 50 −1.4 943 3.0E+09 4.61 4.61March 08, 2006 b.d.l. 1.50 0.43 96.80 62 −1.4 n.d n.d n.d n.d

5 Tito (N 40° 34′ 4.1″; E 15° 41′ 18″) Apennines chain Dissolved cm3 STP/l cm3 STP/l cm3 STP/l cm3 STP/l cm3 STP/lJuly 09, 2006 0.02 11.10 6.20 8.77 1.3E−03 n.d. 13.98 n.d. 0.14 0.12December 19, 2006 0.02 15.50 7.38 8.59 7.5E−04 n.d. 9.67 n.d. 0.14 0.11September 29, 2007 0.00 14.84 0.07 8.66 1.1E−03 n.d. 9.42 n.d. 0.15 0.12

12 Pozzo Fore (N 41° 02′ 56.7″; E 15° 54′ 27.8″) Foreland DissolvedSeptember 21, 2005 0.02 11.39 0.41 278.4 195 n.d. 68.3 n.d. 2.99 3.00

Notes: (R/Ra)c is R/Ra corrected by atmospheric contamination according to Giggenbach et al. (1993). n.d. = not detected.a Data from Italiano et al. (2000, 2001).

69A.Caracausiet

al./JournalofV

olcanologyand

Geotherm

alResearch253

(2013)65

–74

Fig. 2. Comparison of 3He/4He from cogenetic olivine and pyroxene (cpx) from theVulture samples. Samples abbreviations as Table 2.

Fig. 4. 3He/4He vs 87Sr/86Sr of sampled rocks.

70 A. Caracausi et al. / Journal of Volcanology and Geothermal Research 253 (2013) 65–74

derived by subduction-related addition of crustal helium and/or radio-genic decay of U and Th.

4.2. Geochemistry of the fluids

The chemical composition of the fluids, together with the dataon 3He/4He, 4He/20Ne and carbon isotope compositions (δ13C) ofcarbon dioxide, are reported in Table 2. We focus our attentionon 3He/4He since they provide the clearest indication of fluidsources (mantle, crust and atmosphere). The fluid 3He/4He can becompared with the magmatic value measured in the Mt. Vulturelavas. Carbon isotope values rarely provide unambiguous informa-tion on the source of carbon in crustal fluids. In gases and watersin southern Italy, for instance, δ13C of mantle-magmatic CO2 andcrustal-metamorphic CO2 overlap at values between +2‰ and −3‰(Gambardella et al., 2004). Additional information about the fluidsources and interaction histories are provided by CO2/3He ratios.CO2/3He is remarkably uniform in gases from mantle-derived magmas(between 109 and 1010, e.g. Ballentine and Burnard, 2002) but variesin response to processes occurring during the route to the surface(gas dissolution into aquifers, addition of crustal gases, degassing, etc.).

All the sampled free gases show b0.5% O2 indicating trivial incor-poration of atmosphere. This is supported by the high 4He/20Ne ratios(from 6 to 1400) (Table 2). Free gases are generally CO2-rich, exceptPaestum and S. Cataldo that are dominated by N2. This suggests thatthe gases have a variety of sources and/or transport modes. In the fol-lowing we will describe the variation of helium isotopic compositionfrom NE to SW (Figs. 6 and 7).

Fig. 3. 3He/4He vs [He] for phenocrysts from the Mt. Vulture volcano.

The CO2/3He and 3He/4He of the fluids are highly variable(Fig. 6). 3He/4He values range from 0.1 Ra (Tito) to 6.3 Ra (Mt. Vulture),while CO2/3He ratios from 2.7×108 (San Cataldo) to 2.1×1011 (Mt.Vulture). At Pozzo Fore in the Apulian foreland to east of Mt. Vulture,the groundwater has 3He/4He=3.0 Ra. The CO2-rich gases of Maschitohave 3He/4He of 4.6 Ra (Fig. 7 and Table 2). This site is located 20 kmfrom Mt. Vulture, along the NW–SE tectonic lineament crossing theLago Grande of Monticchio and the other centers of diatreme activity(Giannandrea et al., 2006). The 3He/4He of Maschito is within therange of values measured in Mt. Vulture gas emissions, suggesting alink with the volcanic degassing of Mt. Vulture. This implies a tectoniccontrol on the movement of fluids in the region. δ13CCO2 (−1.4‰) isin the range of values reported for volcanic gases of central Italy(Gambardella et al., 2004) andCO2/3He ratio (3.0×109) is indistinguish-able from typical mantle values. We therefore suggest that theMaschitogas emission is fed by magmatic intrusions at depth that are geneticallylinked to the Mt. Vulture magmatic system. This is in accordance withearlier geophysical investigations that have revealed a sill-like intrusionbeneath Maschito (Florio et al., 2009).

The 3He/4He of free gases emanating on the flanks of Mt. Vultureare similar to those reported in Caracausi et al. (2008), ranging be-tween 6.3 Ra and 4.3 Ra. CO2/3He ratios (~1011) are high for volcanicsystems (between 109 and 1010, e.g. Ballentine and Burnard, 2002,Fig. 6). CO2/3He in excess of 109 are typically produced by the addi-tion of crustal CO2 (Ballentine and Burnard, 2002). However, thiscan be excluded as it should be accompanied by the addition ofcrustal-radiogenic He. The 3He/4He of free gases overlaps the highvalues measured in melt inclusions in phenocryst olivine andclinopyroxene, suggesting that the gases are largely free from crustalcontribution. The high CO2/3He ratios are, in this case, likely due toopen system degassing of aquifers previously fed by the volcanic

Fig. 5. 3He/4He vs. age of the rocks (see Table 1). The empty rectangle indicates theisotopic range in the fluids currently emitted from Mt. Vulture. The values of P6 andV10 samples are overlapped.

Fig. 6. CO2/3He vs 3He/4He measured in gas emissions along and in proximity of theVulture line. The MORB and European subcontinental mantle (ESCM) values fromBallentine and Burnard (2002) and Bräuer et al. (2004), respectively. Data of gasemissions from Mt Etna are also shown (Naftia, Stadio, Vallone Salato and P39 sites,Caracausi et al., 2003 and Rizzo et al., 2006). While CO2/3He data from Mt Vultureare dominated by aquifer degassing, Mt Etna data display lower values becausethey represent residual gases after interaction with aquifers (Caracausi et al., 2003).

71A. Caracausi et al. / Journal of Volcanology and Geothermal Research 253 (2013) 65–74

gases. CO2 is significantly (by a factor ~100 at 20 °C) more soluble ingroundwater than He (Snyder et al., 2001; Porcelli et al., 2002). Conse-quently open system (Rayleigh-type) degassing, possibly driven bywater de-pressurization along faults, is able to strongly increase theCO2/3He ratio of the exsolved gas phase. This is consistent with thewidespread occurrence of CO2-bubbling waters in the Mt. Vulture area(Paternoster et al., 2010; Parisi et al., 2011a, 2011b). Similarly, in anold volcanic area of Central Europe, Bräuer et al. (2004) reported highvalues of CO2/3He ratios (about 10+11) due tomassive helium strippingby Rayleigh fractionation, driven by solubility differences betweenhelium and carbon dioxide in groundwater.

To the SW, the 3He/4He of fluids displays a clear decreasing trend,down to 1.35 Ra at Contursi, 1.33 Ra at S. Sisto and 0.77 Ra at Paestum.These values, similar to the data measured by Italiano et al. (2000,2001), are measurably lower than the Mt. Vulture–Maschito area,but still have an unambiguous mantle-derived helium contribution.The relatively high CO2/3He ratio of S. Sisto and Contursi (from2×1010 to 1011, Fig. 6) could be ascribed to degassing fractionation,analogously to Mt. Vulture samples or alternatively, given that thecontribution of crustal gases is evident from He isotopes, to additionof carbon dioxide of crustal origin.

The gases emitted at Paestum have CO2/3He ratio (0.6×109) thatis slightly lower than magmatic values, high N2 concentration (86%),and δ13CCO2 shifted towards negative values (−9.3‰). This may beexplained by the addition of N2 during gas transport in the crust, to-gether with a partial CO2 dissolution in groundwater. A contributionof organic CO2 is required to explain the δ13CCO2. In contrast to thesefluids, gases from S. Cataldo and Tito, to the south of the transect, dis-play the lowest 3He/4He (~0.1 Ra), as already reported by Italiano

Fig. 7. Geographic transect of the 3He/4He (in R/Ra corrected for atmosphericcontamination) values along the Vulture line (location in Fig. 1).Continental and crustal radiogenic range after Hoke et al. (2000).

et al. (2001). This implies an origin in the continental crust rocks,and a negligible contribution of helium from the mantle (Table 2).The S. Cataldo gases display δ13CCO2 (−12.5‰) indicative of an or-ganic contribution. The low CO2/3He ratio of S. Cataldo and Paestumgases (Fig. 6) is probably due to low gas flux (bubbles in water) thatpermits preferential dissolution of CO2 into water relative to helium,thus decreasing the CO2/3He ratio in the residual gas phase. Unfortu-nately, no air-free gas emissions, necessary to detect precise 3He/4Heand CO2/3He ratios are present north of the transect, so that the ab-sence of a contribution of magmatic gas cannot be demonstrated inthat area. The huge gas emission know as Mefite d'Ansanto locatesabout 30 km northward of the Vulture line and has been the focusof different studies that demonstrated that it is due to a local peculiarphenomenon of magma intrusion into the crust. Mefite d'Ansanto isthe largest CO2 emission in non-volcanic environment a worldwidescale (Italiano et al., 2000; Rogie et al., 2000; Chiodini et al., 2010).

Along the Vulture line, the highest contribution of mantle-derivedfluids is present at Mt. Vulture volcano, while it decreases towardthe Tyrrhenian sea. This may be due to different causes: a) volatilesdegassing from near-surface melts beneath Mt. Vulture are quantita-tively dominant with respect to crustal gases, in contrast to gas emis-sions located close to the peri-Thyrrenian area and/or b) the 3He/4Heof the peri-Tyrrhenian magmas is expected to be lower than 6 Ra. Therelatively low 3He/4He of the Vesuvio and Campi Flegrei volcanoes(b4 Ra) was noticed on the basis of free gas sampling (Hooker et al.,1985; Sano et al., 1989; Tedesco et al., 1990; Tedesco, 1997) and con-firmed by measurement in olivine and pyroxene phenocrysts of basiclavas (Graham et al., 1993; Martelli et al., 2004). The reason for suchlow ratios is the contamination of mantle wedge operated by the sub-duction of Ionian–Adriatic slab, as also evidenced by other geochem-ical tracers (trace elements and isotopic ratios of lithophile elements,e.g. Peccerillo, 1985).

5. Geodynamic implications

The geochemical investigation highlights that mantle-derivedhelium is emitted along the NE–SW transect of the Vulture line, fromthe Apulian foreland to the Tyrrhenian sea (Fig. 7). The transfer of man-tle volatiles (i.e., CO2, He) into the crust cannot occur without mantlemelting at depth (Watson and Brenan, 1987; Brenan and Watson,1988). The emission of mantle-derived volatiles in continental regionsis related to sub-surface magmatism (e.g., O'Nions and Oxburgh, 1988;Marty et al., 1992; Italiano et al., 2000; Ballentine and Burnard, 2002;Caracausi et al., 2005; Bräuer et al., 2009). The data presented here im-plies that partial melting of the mantle and intrusion of the magmainto the deep crust is occurring along the length of the tectonic discon-tinuity. The main fault systems appears to be the means throughwhich the melt intrudes into the crust and degassed volatiles move to-wards the surface, in a manner similar to that proposed for the SanAndreas fault (Kennedy and Van Soest, 2007).

The tectonic discontinuity reconciles the occurrence of theMt. Vulturevolcano significantly further east than the subduction-related volcanismof the peri-Tyrrhenian margin of the southern segment of the Italianpeninsula. The presence of melt accumulations along this transect israther unexpected, because the Vulture line crosses an entire sectionof the orogenic belt and of the Apulian foreland and foredeep wherethere is no evidence of volcanism. As already noted, the highest contri-bution of mantle-derived fluids is measured at Mt. Vulture volcano andthe surrounding area. In the Apulian foreland and foredeep, a contribu-tion of mantle-derived helium (3.0 Ra and 4.6 Ra) was found at PozzoFore and Maschito site, respectively. Our geochemical evidence for thepresence of magma below the southern Apennines is well supportedby geophysical investigations. On the basis of the deep structurerevealed by seismic tomography (Lucente et al., 1999), Rosenbaumet al. (2008) confirm the presence of a slab tear fault at depth of100–340 km with NE–SW surface orientation. The process of slab

72 A. Caracausi et al. / Journal of Volcanology and Geothermal Research 253 (2013) 65–74

tearing creates gaps in the lithosphere that allows asthenospheric up-welling. This likely results in decompression melting. The degassing ofthese magma bodies during their up-rise towards the surface andtheir successive crystallization exsolves mantle helium into the deepcrust that can leak up the Vulture line fracture system. Such model issimilar to that of Doglioni et al. (2001) for the Mount Etna where thelarger southeastward subduction rollback of the Ionian lithospherewith respect to the Hyblean plateau produces lateral transtension anda sort of vertical ‘slab window’ through which mantle melts may riseto form the Mt Etna volcano.

In a study by Ökeler et al. (2009), waveform modeling of regionalsurface waves showed that partial melting of mantle due to astheno-spheric upwelling is occurring beneath the southern Apennines. Theseauthors stipulated that less than 2% partial melt is needed to explainthe observed velocity perturbation (a low-velocity body within thecrust) beneath the southern Apennines. Also, an interpretation of aero-magnetic data by scaling function methods (Florio et al., 2009), recog-nized three anomalies between 5 km and 20 km of depth under theMt. Vulture area which indicates the presence of intrusions, probablylinked to the past activity of Mt. Vulture volcano. Finally, Cella andFedi (2012), on the basis of an inversion of potentialfield data, highlightthe presence of intrusive mafic bodies located in correspondence of theVulture line, just a few of kilometers from Mt. Vulture. As alreadysuggested, slab tear and/or break-off near crustal depths offer attractivemechanism for extrusion of partial melting to relatively shallow depths.Hence, our data in conjunction with the studies of Rosenbaum et al.(2008) suggest the active role of lithospheric faults to transfer towardsthe surface mantle-derived fluids from magmatic bodies or from as-thenospheric upwelling of hot, possible molten material (Ökeler et al.,2009) accumulated to the base of the crust.

6. Conclusions

Olivine and clinopyroxene from various Mt. Vulture volcanic rocksconstrain the 3He/4He ratio of the mantle source at 6 Ra. This value israther constant along the history of the volcano, is the highest of theItalian peninsular magmatism and slightly lower than that of themost uncontaminated Sicilian terms. Very similar helium isotopic ra-tios (up to 6.3 Ra) are measured in free and dissolved gases sampledat Mt. Vulture, indicating that magmatic degassing is still ongoing de-spite the most recent eruptive activity dates back to about 140 kyr.The active degassing of mantle-derived fluids along the investigatedtransect tracing the tectonic discontinuity called the Vulture line isconsistent with the presence of a vertical slab window, produced bydifferent roll-back velocities along the subducting slab and conse-quent slab tearing. We suggest that mantle fluids rise along such lith-ospheric tear fault.

Helium isotopes suggest that Mt. Vulture mantle source is character-ized by anorogenic-intraplate mantle signature with a modest contribu-tion of a subduction-type component. The noticed current degassing ofmantle fluids with the same characteristics of those emitted during thepast eruptive activity allows a tight comparison between Mt. Vultureand the active volcanoes of the southern Italy. In particular, we underlinethe tectonic and geodynamic analogies linking Mt. Vulture and Mt. Etnavolcanoes. Both are situated on the margin of the foreland, along-dipvertical slab windows (Doglioni et al., 1994; Schiattarella et al., 2005;D'Orazio et al., 2007), most likely having a role also in imprinting theambiguous characters (intraplate plusminor subduction-related compo-nent) of the mantle sources in both areas (Schiano et al., 2001; De Astiset al., 2006), and through which mantle fluids can reach the surface.

Acknowledgments

Thanks to Rob Ellam for strontium isotope analyses. This work ispart of the Ph.D. thesis of M.P. supported by the European SocialFund and Istituto Nazionale di Geofisica e Vulcanologia (Palermo).

The paper greatly benefited from the constructive criticism of twoanonymous reviewers.

References

Ballentine, C.J., Burnard, P.G., 2002. Production, release and transport of noble gases inthe continental crust. Reviews in Mineralogy and Geochemistry 47, 481–538.

Bartolini, C., D'Agostino, N., Dramis, F., 2003. Topography, exhumation, and drainagenetwork evolution of the Apennines. Episodes 26, 212–216.

Beccaluva, L., Coltorti, M., Di Girolamo, P., Melluso, L., Dilani, L., Morra, V., Siena, E., 2002.Petrogenesis and evolution ofMt. Vulture alkaline volcanism (Southern Italy). Miner-alogy and Petrology 74, 277–297.

Bentivenga, M., Coltorti, M., Prosser, G., Tavarnelli, E., 2004. A new interpretation of terracesin the Taranto Gulf: the role of extensional faulting. Geomorphology 60, 383–402.

Bianchini, G., Beccaluva, L., Siena, F., 2008. Post-collisional and intraplate Cenozoicvolcanism in the rifted Apennines/Adriatic domain. Lithos 101, 125–140.

Billi, A., Barberi, G., Faccenna, C., Neri, G., Pepe, F., Sulli, A., 2006. Tectonics and seismicity ofthe Tindari Fault System, southern Italy: crustal deformations at the transition betweenongoing contractional and extensional domains located above the edge of a subductingslab. Tectonics 25, TC2006 http://dx.doi.org/10.1029/2004TC001763 (20 pp.).

Bräuer, K., Kämpf, H., Niedermann, S., Strauch, G., Weise, S.M., 2004. Evidence for a nitro-gen flux directly derived from the European subcontinental mantle in the WesternEger Rift, central Europe. Geochemistry, Geophysics, Geosystems 68, 4935–4947.

Bräuer, K., Kämpf, H., Strauch, G., 2009. Earthquake swarms in non-volcanic regions:what fluids have to say. Geophysical Research Letters 36 http://dx.doi.org/10.1029/2009GL039615.

Brenan, J.M., Watson, E.B., 1988. Fluids in the lithosphere 2: experimental constrains onCO2 trasport in dunite and quartzite at elevated P–T conditions with implicationsfor mantle and crust decarbonation processes. Earth and Planetary Science Letters91, 141–158.

Brocchini, D., La Volpe, L., Laurenzi, M.A., Principe, C., 1994. Storia evolutiva del M. Vul-ture. Plinius 12, 22–25.

Büettner, A., Principe, C., Villa, I.M., Bocchini, D., 2006. 39Ar–40Ar geochronology ofMonte Vulture. In: Principe, C. (Ed.), La Geologia del Monte Vulture. GraficheFiniguerra, Lavello, Italy, pp. 73–86.

Capasso, G., Inguaggiato, S., 1998. A simple method for the determination of dissolvedgases in natural waters. An application to thermal waters from Vulcano Island.Applied Geochemistry 13, 631–642.

Caracausi, A., Italiano, F., Paonita, A., Rizzo, A., 2003. Evidence of deep magma degassingand ascent by geochemistry of peripheral gas emissions at Mount Etna (Italy): as-sessment of the magmatic reservoir pressure. Journal of Geophysical Research 108,2463–2477.

Caracausi, A., Favara, R., Italiano, F., Nuccio, P.M., Paonita, A., Rizzo, A., 2005. Activegeodynamics of the central Mediterranean sea: tensional tectonic evidences inwestern Sicily from mantle derived helium. Geophysical Research Letters 32,L04312 http://dx.doi.org/10.1029/2004GL0216098.

Caracausi, A., Nuccio, P.M., Favara, R., Nicolosi, M., Paternoster, M., 2008. Gas hazard as-sessment at the Monticchio crater lakes of Mt. Vulture, a volcano in southern Italy.Terra Nova 21, 83–87.

Cella, F., Fedi, M., 2012. Inversion of potential field data using the structural index asweighting function rate decay. Geophysical Prospecting 60, 313–336.

Chiodini, G., Cardellini, C., Amato, A., Boschi, E., Caliro, S., Frondini, F., Ventura, G., 2004.Carbon dioxide Earth degassing and seismogenesis in central and southern Italy.Geophysical Research Letters 31, L07615 http://dx.doi.org/10.1029/2004GL019480.

Chiodini, G., Granieri, D., Avino, R., Caliro, S., Costa, A., Minopoli, C., Vilardo, G., 2010. Non-volcanic CO2 Earth degassing: case of Mefite d'Ansanto (southern Apennines), Italy.Geophysical Research Letters 37, L11303 http://dx.doi.org/10.1029/2010GL04285.

Correale, A., Martelli, M., Paonita, A., Rizzo, A., Brusca, L., Scribano, V., 2012. New evidenceof mantle heterogeneity beneath the Hyblean Plateau (southeast Sicily, Italy) as in-ferred from noble gases and geochemistry of ultramafic xenoliths. Lithos 132–133,70–81.

Coulson, I.M., Stuart, F.M., MacLean, N.J., 2011. Assessing the link between mantlesource and sub-volcanic plumbing in the petrology of basalts from the 2001 and2002/2003 eruptions of Mount Etna, Sicily: evidence from geochemical and heliumisotope data. Lithos 123, 254–261.

De Astis, G., Kempton, P.D., Peccerillo, A., Wu, T.W., 2006. Trace element and isotopicvariations from Mt. Vulture to Campanian volcanoes: constraints for slab detach-ment and mantle inflow beneath southern Italy. Contributions to Mineralogy andPetrology 151, 331–351.

De Fino, M., La Volpe, L., Piccarreta, G., 1982. Magma evolution at the Mount Vulture(Southern Italy). Bulletin of Volcanology 45, 115–126.

De Fino, M., La Volpe, L., Peccerillo, A., Piccarreta, G., 1986. Petrogenesis of MountVulture volcano (Italy): inferences from mineral chemistry, major and trace ele-ments data. Contributions to Mineralogy and Petrology 17, 135–145.

Di Luccio, F., Piscini, A., Pino, N.A., Ventura, G., 2005. Reactivation of deep faults beneathSouthern Apennines: evidence from the 1990–1991 Potenza seismic sequences.Terra Nova 17, 586–590.

Doglioni, C., Mongelli, F., Pieri, P., 1994. The Puglia uplift (SE Italy): an anomaly in theforeland of the Apenninic subduction due to buckling of a thick continental litho-sphere. Tectonics 13 (5), 1309–1321.

Doglioni, C., Harabaglia, P., Merlini, S., Mongelli, F., Peccerillo, A., Piromallo, C., 1999.Orogens and slabs vs. their direction of subduction. Earth-Science Reviews 45,167–208.

Doglioni, C., Innocenti, F., Mariotti, S., 2001. Why Mt. Etna? Terra Nova 13, 25–31.

73A. Caracausi et al. / Journal of Volcanology and Geothermal Research 253 (2013) 65–74

Doglioni, C., Carminati, E., Cuffaro, M., Scrocca, D., 2007. Subduction kinematics anddynamic constraints. Earth-Science Reviews 83, 125–175.

D'Orazio, M., Innocenti, F., Tonarini, S., Doglioni, C., 2007. Carbonatites in a subductionsystem: the Pleistocene alvikites from Mt. Vulture (southern Italy). Lithos 98,313–334.

D'Orazio, M., Innocenti, F., Tonarini, S., Doglioni, C., 2008. Reply to the discussionof:“Carbonatites in a subduction system: The Pleistocene alvikites fromMt. Vulture(Southern Italy)” by M. D'Orazio, F. Innocenti, S. Tonarini and C. Doglioni (Lithos98, 313–334) by F. Stoppa, C. Principe and P. Giannandrea. Lithos 103, 557–561.

Downes, H., Kostoula, T., Jones, A.P., Beard, A.D., Thirlwall, M.F., Bodinier, J.L., 2002.Geochemistry and Sr–Nd isotopic compositions of mantle xenoliths from theMonte Vulture carbonatite–melilitite volcano, central southern Italy. Contributionsto Mineralogy and Petrology 144, 78–92.

Farley, K.A., Neroda, E., 1998. Noble gases in the Earth's mantle. Annual Review of Earthand Planetary Sciences 26, 189–218.

Florio, G., Fedi, M., Rapolla, A., 2009. Interpretation of regional aeromagnetic data bythe scaling function method: the case of Southern Apennines (Italy). GeophysicalProspecting 57, 479–489.

Frepoli, A., Amato, A., 2000. Spatial variation in stresses in Peninsular Italy and Sicilyfrom background seismicity. Tectonophysics 317, 109–124.

Frepoli, A., Cinti, F.R., Amicucci, L., Cimini, G.B., De Gori, P., Pierdominici, S., 2005. Patternof seismicity and state of stress in the Lucanian Apennines and foredeep (southernItaly) from recording by the Saptex Temporary Array. Annals of Geophysics 48 (6),1035–1054.

Gambardella, B., Cardellini, C., Chiodini, G., Frondini, F., Marini, L., Ottonello, G., VetuschiZuccolini, M., 2004. Fluxes of deep CO2 in the volcanic areas of central southernItaly. Journal of Volcanology and Geothermal Research 136, 31–52.

Giannandrea, P., La Volpe, L., Principe, C., Schiattarella, M., 2006. Unità stratigrafiche a limitiinconformi e storia evolutiva del vulcano medio-pleistocenico di Monte Vulture(Appenninomeridionale, Italia). Bollettino della Societa Geologica Italiana 125, 67–92.

Giggenbach, W.F., Sano, Y., Wakita, H., 1993. Isotopic composition of helium, and CO2and CH4 contents in gases produced along the New Zealand part of a convergentplate boundary. Geochimica et Cosmochimica Acta 57, 3427–3455.

Govers, R., Wortel, M.J.R., 2005. Lithosphere tearing at STEP faults: response to edges ofsubduction zones. Earth and Planetary Science Letters 236, 505–523.

Graham, D.W., Allard, P., Kilburn, C.R.J., Spera, E.J., Lupton, J.E., 1993. Helium isotopes insome historical lavas from Mount Vesuvius. Journal of Volcanology and GeothermalResearch 58, 359–366.

Güleç, N., Hilton, D.R., Mutlu, H., 2002. Helium isotope variations in Turkey: relationshipto tectonics, volcanism and recent seismic activities. Chemical Geology 187 (1–2),129–142.

Hilton, D.R., Fischer, T.P., Marry, B., 2002. Noble gases and volatile recycling at subductionzone. In: Porcelli, D., Ballentine, C.J., Wieler, R. (Eds.), Noble Gases in Geochemistryand Cosmochemistry. : Reviews in Mineralogy and Geochemistry, 47. MineralogicalSociety of America and Geochemical Society, Zurich, Switzerland, pp. 319–370.

Hoke, L., Lamb, S., Hilton, D.R., Poreda, R.J., 2000. Southern limit of mantle-derived geo-thermal helium emissions in Tibet: implications for lithospheric structure. Earthand Planetary Science Letters 180, 297–308.

Hooker, P.J., Bertrami, R., Lombardi, S., O'Nions, R.K., Oxburg, E.R., 1985. Helium-3anomalies and crust mantle interactions in Italy. Geochimica et CosmochimicaActa 49, 2505–2513.

Italiano, F., Martelli, M., Martinelli, G., Nuccio, P.M., 2000. Geochemical evidence of meltintrusions along lithospheric faults of the southern Apennines (Italy): geodynamicand seismogenic implications. Journal of Geophysical Research 106, 13569–13578.

Italiano, F., Martelli, M., Martinelli, G., Nuccio, P.M., 2001. Significance of earthquake-related anomalies in fluids of Val D'Agri (Southern Italy). Terra Nova 13 (4), 249–257.

Jones, A.P., Kostoula, T., Stoppa, F., Woolley, A.R., 2000. Petrography and mineral chem-istry of mantle xenoliths in a carbonate-rich melilititic tuff from Mt. Vulture volca-no, Southern Italy. Mineralogical Magazine 64, 593–613.

Kennedy, B.M., Van Soest, M., 2007. Flow of mantle fluids through the ductile lowercrust: helium isotope trends. Science 318, 1433–1436.

Kennedy, B.M., Kharaka, Y.K., Evans, W.C., Ellwood, A., DePaolo, D.J., Thordsen, J., Ambats,G., Mariner, R.H., 1997. Mantle fluids in the San Andreas fault system, California.Science 278, 1278–1281.

King, C.Y., 1986. Gas geochemistry applied to earthquake prediction: an overview.Journal of Geophysical Research 91 (B12), 12269–12281 http://dx.doi.org/10.1029/JB091iB12p12269.

Kulongoski, J.T., Hilton, D.R., Izbicki, J.A., 2003. Helium isotope studies in the MojaveDesert, California: implications for groundwater chronology and regional seismicity.Chemical Geology 202, 95–113.

Lucente, F.P., Chiarabba, C., Cimini, D., Giardini, G.B., 1999. Tomographic constraints onthe geodynamic evolution of the Italian region. Journal of Geophysical Research104, 20307–20327.

Malinverno, A., Ryan, W.B.F., 1986. Extension in the Tyrrhenian sea and shortening inthe Apennines as a result of arc migration driven by sinking of the lithosphere.Tectonics 5, 227–245.

Martelli, M., Nuccio, P.M., Stuart, F.M., Burgess, R., Ellam, R.M., Italiano, F., 2004. Helium–

strontium isotope constraints on mantle evolution beneath the Roman ComagmaticProvince, Italy. Earth and Planetary Science Letters 224 (3–4), 295–308 http://dx.doi.org/10.1016/j.epsl.2004.05.025.

Martelli, M., Nuccio, P.M., Stuart, F.M., Di Liberto, V., Ellam, R.M., 2008. Constraints onmantle source and interactions from He–Sr isotope variation in Italian Plio-Quaternary volcanism. Geochemistry, Geophysics, Geosystems 9, Q02001 http://dx.doi.org/10.1029/2007GC001730.

Marty, B., O'Nions, R.K., Oxburgh, E.R., Martel, D., Lombardi, S., 1992. Helium isotopes inAlpine regions. Tectonophysics 206, 71–78.

Marty, B., Trull, T., Luzziez, P., Basile, I., Tanguy, J.C., 1994. He, Ar, O, Sr and Nd isotopeconstraints on the origin and evolution of Mount Etna magmatism. Earth and Plan-etary Science Letters 126, 23–39.

Montone, P., Mariucci, M.T., Pondrelli, S., Amato, A., 2004. An improved stress mapfor Italy and surrounding regions (Central Mediterranean). Journal of GeophysicalResearch 109, B10410 http://dx.doi.org/10.1029/2003JB002703.

Nuccio, P.M., Paonita, A., Rizzo, A., Rosciglione, A., 2008. Elemental and isotope covariationof noble gases in mineral phases from Etnean volcanics erupted during 2001–2005,and genetic relation with peripheral gas discharges. Earth and Planetary Science Let-ters 272, 683–690.

O'Nions, R.K., Oxburgh, E.R., 1988. Helium, volatile fluxes and the development of con-tinental crust. Earth and Planetary Science Letters 90, 331–347.

Ökeler, A., Gu, Y.J., Lerner-Lam, A., Steckler, M.S., 2009. Seismic structure of the southernApenninesas revealed bywaveformmodelling of regional surfacewaves. GeophysicalJournal International 178, 1473–1492.

Parello, F., Allard, P., D'Alessandro, W., Federico, C., Jean-Baptiste, P., Catani, O., 2000. Iso-tope geochemistry of Pantelleria volcanic fluids, Sicily Channel rift: a mantle volatileend-member for volcanism in southern Europe. Earth and Planetary Science Letters180, 325–339.

Parisi, S., Paternoster, M., Kohfahl, C., Pekdeger, A., Meyer, H., Hubberten, H.W., Spilotro, G.,Mongelli, G., 2011a. Groundwater recharge areas of a volcanic aquifer system inferredfrom hydraulic, hydrogeochemical and stable isotope data: Mount Vulture, southernItaly. Hydrogeology Journal 19, 133–153.

Parisi, S., Paternoster, M., Perri, F., Mongelli, G., 2011b. Source and mobility of minor andtrace elements in a volcanic aquifer system: Mt. Vulture (southern Italy). Journal ofGeochemical Exploration 110, 233–244.

Paternoster, M., Parisi, S., Caracausi, A., Favara, R., Mongelli, G., 2010. Groundwaters ofMt. Vulture volcano, southern Italy: chemistry and sulfur isotope composition ofdissolved sulphate. Geochemical Journal 44, 125–135.

Peccerillo, A., 1985. Roman comagmatic province (central Italy): evidence for subduction-related magma genesis. Geology 13 (2), 103.

Peccerillo, A., 2005. Plio-Quaternary Volcanism in Italy. Springer, New York, p. 379.Pik, R., Marty, B., 2009. Helium isotopic signature of modern and fossil fluids associated

with the Corinth rift fault zone (Greece): implication for fault connectivity in thelower crust. Chemical Geology 266 (1–2), 67–75.

Piromallo, C., Morelli, A., 2003. P wave tomography of the mantle under the Alpine–Mediterranean area. Journal of Geophysical Research 108 (B2), 2065 http://dx.doi.org/10.1029/2002JB001757.

Poliak, B.G., Tolstikin, I.N., 1979. Geotectonics, heat flux and helium isotopes: triplerelationship. Paper presented at International Symposium of Gooch. Soc. of USSR,Leningrado.

Pondrelli, S., Morelli, A., Ekstrom, G., Mazza, S., Boschi, E., Dziewonski, A.M., 2002.European–Mediterranean regional centroid-moment tensors: 1997–2000. Physicsof the Earth and Planetary Interiors 130, 71–101 (Quick Regional CMT availableat: http://mednet.ingv.it/events/QRCMT/Welcome.html).

Porcelli, D., Ballantine, C.J., Wieler, R., 2002. Noble gases in geochemistry and cosmo-chemistry. In: Porcelli, D., Ballentine, C.J., Wieler, R. (Eds.), Noble Gases inGeochemistry and Cosmochemistry. : Reviewes in Mineralogy and Geochemistry,47. Mineralogical Society of America and Geochemical Society, Zurich, Switzerland,pp. 1–844.

Rizzo, A., Caracausi, A., Favara, R., Martelli, M., Paonita, A., Paternoster, M., Nuccio, P.M.,Rosciglione, A., 2006. New insights into magma dynamics during last two erup-tions of Mount Etna as inferred by geochemical monitoring from 2002 to 2005.Geochemistry, Geophysics, Geosystems 7 (6), Q06008 http://dx.doi.org/10.1029/2005GC001175.

Rogie, J.D., Kerrick, D.M., Chiodini, G., Frondini, F., 2000. Flux measurements ofnonvolcanic CO2 emissions from some vents in central Italy. Journal of GeophysicalResearch 105, 8435–8445.

Rosenbaum, G., Gasparon, M., Lucente, F.P., Peccerillo, A., Miller, M.S., 2008. Kinematicsof slab tear faults during subduction segmentation and implications for Italianmagmatism. Tectonics 27 http://dx.doi.org/10.1029/2007TC002143.

Sano, Y., Wakita, H., Italiano, F., Nuccio, M.P., 1989. Helium isotopes and tectonics insouthern Italy. Geophysical Research Letters 16, 511–514.

Sapienza, G., Hilton, D.R., Scribano, V., 2005. Helium isotopes in peridotite mineralphases from Hyblean Plateau (south-eastern Sicily, Italy). Chemical Geology 219,115–129.

Schellart, W.P., Freeman, J., Stegman, D.R., Moresi, L., May, D., 2007. Evolution and di-versity of subduction zones controlled by slab width. Nature 446, 308–311.

Schiano, P., Clocchiatti, R., Ottolini, L., Busa, T., 2001. Transition of Mount Etna lavasfrom a mantle-plume to an island-arc magmatic source. Nature 412, 900–904.

Schiattarella, M., Beneduce, P., Giano, S.I., Giannandrea, P., Principe, C., 2005. Assettostrutturale ed evoluzione morfotettonica quaternaria del vulcano del Monte Vulture(Appennino Lucano). Bollettino della Societa Geologica Italiana 124, 543–562.

Scrocca, D., 2006. Thrust front segmentation induced by differential slab retreat in theApennines (Italy). Terra Nova 18, 154–161.

Scrocca, D., Carminati, E., Doglioni, C., 2005. Deep structure of the southern Apennines,Italy: thin-skinned or thick-skinned? Tectonics 24, TC 3005 http://dx.doi.org/10.1029/2004TC001634.

Shaw, A.M., Hilton, D.R., Fisher, T.P., Walker, J.A., de Leeuw, G.A., 2006. Helium iso-tope variations in mineral separates from Costa Rica and Nicaragua: assessingcrustal contributions, timescale variations and diffusion-related mechanisms.Chemical Geology 230, 124–129.

Snyder, G., Poreda, R., Hunt, A., Fehn, U., 2001. Regional variationsin volatile com-position: isotopic evidence for carbonate recyclingin the Central American vol-canic arc. Geochemistry, Geophysics, Geosystems 2 http://dx.doi.org/10.1029/2001GC000161.

74 A. Caracausi et al. / Journal of Volcanology and Geothermal Research 253 (2013) 65–74

Stoppa, F., Principe, C., 1997. Eruption style and petrology of a new carbonatitic suitefrom the Mt. Vulture (Southern Italy): the Monticchio Lakes formation. Journal ofVolcanology and Geothermal Research 78, 251–265.

Stoppa, F., Woolley, A.R., 1997. The Italian carbonatites: field occurrence petrology andregional significance. Mineralogy and Petrology 59, 43–67.

Stoppa, F., Principe, C., Giannandrea, P., 2008. Comments on: carbonatites in a subductionsystem: the Pleistocene alvikites from Mt. Vulture (southern Italy) by D'Orazio et al.(2007). Lithos 103, 550–556.

Stuart, F.M., Ellam, R.M., Harrop, P.J., Fitton, J.G., Bell, B.R., 2000. Constraints on mantleplumes from the helium isotopic composition of basalt from the British TertiaryIgneous Province. Earth and Planetary Science Letters 117, 273–285.

Stuart, F.M., Lass-Evans, S., Fitton, J.G., Ellam, R.M., 2003. Extreme 3He/4He in picriticbasalts from Baffin Island: the role of a mixed reservoir in mantle plumes. Nature424, 57–59.

Tedesco, D., 1997. Systematic variations in the 3He/4He ratio and carbon of fumarolicfluids from active volcanic areas in Italy: evidence for radiogenic 4He and crustalcarbon addition by the subducting African plate? Earth and Planetary ScienceLetters 151 (3–4), 255–269.

Tedesco, D., Allard, P., Sano, Y., Wakita, H., Pece, R., 1990. Helium-3 in subaerial andsubmarine fumaroles of CampiFlegrei caldera, Italy. Geochimica et CosmochimicaActa 54, 1105–1116.

Trull, T.W., Kurz, M.D., 1993. Experimentalmeasurements of 3He and 4Hemobility in oliv-ine and clinopyroxene at magmatic temperatures. Geochimica et Cosmochimica Acta57, 1313–1324.

Umeda, K., Ninomiya, A., 2009. Helium isotopes as a tool for detecting concealed activefaults. Geochemistry, Geophysics, Geosystems 10, Q08010 http://dx.doi.org/10.1029/2009GC002501.

Watson, E.B., Brenan, J.M., 1987. Fluids in the lithosphere 1: experimentally-determinedwetting characteristics of CO2–H2O fluids and their implications for fluids transport,host-rock physical properties, and fluid inclusion formation. Earth and PlanetaryScience Letters 85, 497–515.

Williams, A.J., Stuart, F.M., Day, S.J., Phillips, W.M., 2005. Timing and rate of landscape de-velopment in central Gran Canaria, eastern Atlantic Ocean, from cosmogenic 3Heconcentrations in pyroxene microphenocrysts. Quaternary Science Reviews 24,211–222.

Wilson, M., Bianchini, G., 1999. Tertiary–Quaternarymagmatismwithin theMediterraneanand surrounding regions. In: Durand, B., Jolivet, L., Horvath, F., Seranne, M. (Eds.), TheMediterranean Basins: TertiaryExtensionWithin theAlpineOrogen:Geol. Soc. London,vol. 156, pp. 141–168.