Earth and Planetary Science Letters 310 (2011) xxxndashxxx

EPSL-11030 No of Pages 13

Contents lists available at ScienceDirect

Earth and Planetary Science Letters

j ourna l homepage wwwe lsev ie rcom locate eps l

Carbonate-derived CO2 purging magma at depth Influence on the eruptive activity ofSomma-Vesuvius Italy

Luigi Dallai a Raffaello Cioni bc Chiara Boschi a Claudia DOriano c

a CNR-Istituto di Geoscienze e Georisorse Via Moruzzi 1 56124 Pisa Italyb Dip to Scienze della Terra Via Trentino 51 09127 Cagliari Italyc INGV sezione di Pisa Via della Faggiola 32 56126 Pisa Italy

Corresponding author Tel +39 0503152315 faxE-mail addresses dallaiiggcnrit (L Dallai) rcioni

cboschiiggcnrit (C Boschi) dorianopiingvit (C DO

0012-821X$ ndash see front matter copy 2011 Elsevier BV Adoi101016jepsl201107013

Please cite this article as Dallai L et al CVesuvius Italy Earth Planet Sci Lett (201

a b s t r a c t

a r t i c l e i n f o

Article historyReceived 31 January 2011Received in revised form 13 July 2011Accepted 14 July 2011Available online xxxx

Editor RW Carlson

Keywordsstable-isotopemagma geochemistryCO2-degassingVesuvius

Mafic phenocrysts from selected products of the last 4 ka volcanic activity at Mt Vesuvius were investigatedfor their chemical and O-isotope composition as a proxy for primary magmas feeding the system 18O16Oratios of studied Mg-rich olivines suggest that near-primary shoshonitic to tephritic melts experienced a fluxof sedimentary carbonate-derived CO2 representing the early process of magma contamination in the roots ofthe volcanic structure Bulk carbonate assimilation (physical digestion) mainly occurred in the shallow cruststrongly influencing magma chamber evolution On a petrological and geochemical basis the effects of bulksedimentary carbonate digestion on the chemical composition of the near-primary melts are resolved fromthose of carbonate-released CO2 fluxed into magma An important outcome of this process lies in the effect ofexternal CO2 in changing the overall volatile solubility of the magma enhancing the ability of Vesuvius maficmagmas to rapidly rise and explosively erupt at the surface

+39 0503152323unicait (R Cioni)riano)

ll rights reserved

arbonate-derived CO2 purging magma at de1) doi101016jepsl201107013

copy 2011 Elsevier BV All rights reserved

1 Introduction

Significant interaction between mafic magma and crust has beendocumented at volcanic systems set in carbonate basements (egVesuvius Italy Popocatepetl Mexico Merapi Indonesia Ayuso et al1998 Goff et al 2001 Chadwick et al 2007) Carbonate assimilationoccurs to variable extents during magma crystallization and evolutionat shallow crustal levels modifying the overall composition of theresidual melts (Barnes et al 2005 Dallai et al 2004 Freda et al2008 Iacono Marziano et al 2007 2008 Mollo et al 2010) Muchless is known about processes controlling the interaction betweenmantle-derived melts and carbonate and about the effects ofcarbonate-derived CO2 on primitive magmas during their ascent tothe surface (Deegan et al 2010) Understanding the mechanisms ofsuch carbonatemelt interaction is important to resolve the effects ofcarbonate digestion from those of carbonate-released CO2 fluxing intomagma and their possible influence on the eruptive style

Thermal decomposition of carbonate (Stanmore and Gillot 2005)and metamorphicndashmetasomatic reactions (Nabeleck 2007) representthe ldquotype-mechanismsrdquo of magmandashcarbonate interaction (Baker andBlack 1980 Gaeta et al 2009 Wenzel et al 2002) during which amassive exchange of heat and mass occurs producing large amounts

of CO2 available for direct fluxing through the magma Whilecontinuously fluxing the magma at depth CO2 has the potential tochange the composition and solubility of volatile componentsdissolved in the melt (Dixon and Stolper 1995 Papale 1999)promoting an increase of magma explosivity and introducingsubstantial variations in the expected eruption scenarios defined forhazard assessment

The influence of magmandashcarbonate interaction on the compositionof volcanic products from Mt Somma-Vesuvius (SV) one of the mosthazardous volcanoes on a world-wide scale has been repeatedlydebated in the last decades (eg Ayuso et al 1998 Piochi et al 2006Rittmann 1933 Savelli 1967) Among these Authors Rittmann(1933) first proposed the idea that the peculiar composition of therocks was related to the effects of carbonate assimilation in theMesozoic basement of the volcano The idea was successivelydiscarded by Savelli (1967) and recently reviewed and proposed onthe base of isotopic data (Ayuso et al 1998 Civetta et al 2004 DiRenzo et al 2007 Piochi et al 2006) and of experimental petrologydata (Iacono Marziano et al 2007 2008 Mollo et al 2010 Fredaet al 2008 Gaeta et al 2009) The occurrence of skarn andmetasomatized cumulatic ejecta in the products of the major SVexplosive eruptions (Barberi and Leoni 1980) and the presence ofexotic silica-poor alkali and Ca-rich melt inclusions in mafic crystalsof some recent eruptions (Fulignati et al 2001) unequivocallyindicate that interaction between SV magmas and carbonate rockswas pervasive during magma residence and crystallization withinshallow reservoirs (less than 8ndash10 km Auger et al 2001 De Natale

pth Influence on the eruptive activity of Somma-

2 L Dallai et al Earth and Planetary Science Letters 310 (2011) xxxndashxxx

et al 2006 Scaillet et al 2008) The effects of carbonate interactionon mafic magmas feeding the shallow system are instead less definedmainly due to the general absence of primary (or nearly primary)magmas among the SV eruptive products In recent years theseeffects have been investigated using experimental petrology (IaconoMarziano et al 2008) suggesting that alkali-rich tephritic magmasmay be derived from primary shoshonitic melts by assimilation of 10to 20 wt of carbonate

Due to the large difference in 18O16O ratios between sedimentarycarbonate (formed in a low-temperature shallow environment) andmafic (mantle-derived) magmas oxygen isotope systematics are apowerful tool for tracing the process of carbonate addition to near-primary K-rich melts and pyroclastic materials (Dallai et al 2004Frezzotti et al 2007 Gaeta et al 2006) In particular rapid coolingrate of pyroclasts prevents subsolidus re-equilibration of O-isotopecomposition and pre-eruptive compositions are likely preserved (egEiler et al 1997) The present work focuses on the oxygen isotopecomposition of selected mafic crystals extracted from pyroclasticproducts of the last 4 ka of SV activity in order to constrain the roleand processes of magmandashcarbonate interaction in producing thecompositional variability observed in the ldquoprimaryrdquo magmas (fromshoshonites to tephrites) and possibly affecting their explosivity

11 The Somma-Vesuvius magmatic activity

Magmatism in the SV area part of the potassic QuaternaryCampania Province (Southern Italy) has been generally interpretedas related to magma generation in an upper mantle contaminated bymaterial coming from the West-directed subducting Adria-Ionianplates (Peccerillo and Lustrino 2005) An alternative hypothesisinvokes a mantle plume rising beneath the southern Tyrrhenian Seaand contamination by subduction (Gasperini et al 2002) The earlymagmatic products in the SV area date back at about 400 ka(Brocchini et al 2001) A mainly effusive volcanic activity occurreddiscontinuously till about 20 ka leading to the formation of MtSomma stratocone After this period themagmatic activity changed toprevalently explosive and in the period up to 79 AD four caldera-forming Plinian eruptions and several subplinian to mid-intensityash-dominated events occurred (Cioni et al 2008) The activity of thelast 2 ka was characterized by periods of low to mid-intensity maficexplosive eruptions alternated with periods of mainly effusiveactivity In this period the summit cone of Vesuvius was erectedDuring the last 20 ka magma composition changed progressivelyshifting from nearly saturated alkaline melts towards more alkali-richsilica undersaturated products (eg Ayuso et al 1998 Cioni et al2008 Santacroce et al 2008) Effusive and explosive products arerepresented by moderately to highly evolved compositions mainlyvarying from trachybasalts to trachytes from phono-tephrites tophonolites and from tephritebasanite to foidites The substantialabsence of primitive products is characteristic of SV products anddirect information on primary mantle-derived melts can be onlyderived from the study of silicatic melt inclusions in mafic minerals(forsteritic olivine and diopsidic pyroxene) occurring as xenocrysts inmany erupted products (Cioni et al 1998 Marianelli et al 1995Marianelli et al 2005) These xenocrysts have been interpreted asderived from the crystallization of primitive magmas during theirascent or as physical mixing with the most evolved cooler magmasresiding in shallower reservoirs Using the volatile (H2O and CO2)content of these melt inclusions as a proxy for the pressure ofcrystallization of the hosting minerals pressure of about 200ndash300 MPa is derived (Marianelli et al 2005) Geophysical andexperimental petrology data are in agreement with these findingssuggesting the presence of a large volume reservoir at about 8ndash10 kmdepth (Auger et al 2001 Scaillet et al 2008)

The whole volcanic sequence rests on a pile of tectonic unitsdominated by a very thick (possibly more than 10 km according to

Please cite this article as Dallai L et al Carbonate-derived CO2 purgVesuvius Italy Earth Planet Sci Lett (2011) doi101016jepsl20110

Patacca and Scandone 2007) deposit of Mesozoic carbonates(limestones and dolomitic limestones) arranged in a duplex systemData from a geothermal borehole drilled on the southern slope of thevolcano highlight that the first SV magmatic products were inter-layered with a neritic to continental Pleistocene silico-clasticsequence which directly covers the Mesozoic carbonatic basementat a depth of about 1900 m (Brocchini et al 2001) Data onmetamorphic and non-metamorphic carbonate ejecta from thePlinian eruptions (Barberi and Leoni 1980) suggest the predominanceof limestones and dolomitic limestones over pure dolomites

2 Samples

Magmatic mafic xenocrysts of SV products were investigated fortheir oxygen isotope and major and trace elements compositionsSingle high-Mg olivine and diopside crystals from the Plinian productsof the tephri-phonolite to phonolite Avellino (39 ka BP Sulpizio et al2010) and Pompeii Pumice (AD 79 Cioni et al 1995) eruptions fromthe subplinian phono-tephrite to tephri-phonolite Pollena (AD 472Sulpizio et al 2005) eruption and from the phono-tephrite productsof a violent strombolian eruption which occurred in the 8th Centuryfrom a lateral vent in the south-western sector of the volcano (AS2fCioni et al 2008) Despite the large different compositions shown bythese 4 eruptions diopside and forsteritic olivine are ubiquitous intheir products although in different proportions pointing out theimportant role of mixing processes during magma residence in ashallow reservoir and of magma extraction during eruption (Cioniet al 1995 Sigurdsson et al 1990) Diopside and forsteritic olivinehave been also described at SV as fundamental mineral phases inskarns and thermometamorphic rocks (Barberi and Leoni 1980)However ldquonon-magmaticrdquo Mg-rich olivine and clinopyroxene havemajor and trace elements compositions significantly different fromthose of ldquomagmaticrdquo phases (Gilg et al 2001 Fig 1a) Chemicalcomposition was used here in order to characterize the crystalsselected for isotope analyses In fact only large euhedral crystals witha clearly magmatic derivation bordered by glass rims were chosen forthe study Finally crystals with a large amount of melt inclusions werediscarded in order to avoid any influence on the isotopic composition

3 Analytical methods

Crystals were accurately separated from selected juvenile materialof the studied eruptions Pumice and large scoriae clasts were crushedin a steel mortar and then sieved Crystals of olivine and diopsidebetween 2 and 1 mm and 1 and 05 mm were hand picked under thestereomicroscope and glued with a thermoplastic cement on a glassslide Samples showing homogeneous color (unzoned crystals) andwithout inclusions were selected for the successive investigationsfrom a total number of about 100 crystals collected

Composition was determined at the Institute for Mineralogy andPetrology (ETH-Zurich Switzerland) using a JEOL JXA-8200 electronmicroprobe with operating conditions of 15 kV accelerating potential20 nA current and 1ndash10 μm beam size Estimated precision rangesaround 005 wt The detection limit is better than 001 wt for eachelement Major elements compositions of olivine and cpx of the AS2feruption were analyzed by energy dispersive X-ray with an EDAX X-4I using a Philips XL30 scanning electronmicroscope at the Universityof Pisa at an accelerating voltage of 20 kV beam current of 01 nA andworking distance of 10 mm At least 2 analyses per crystal werecarried out in order to avoid using strongly zoned crystals

On the same crystals trace elements analyses were performed atthe IGG-CNR laboratory of Pavia using a laser system consisting of aBrilliant Quantel Q-switched NdYAG laser working at a wavelengthof 266 nm (Tiepolo et al 2003) The ablated material was carried byan argonndashhelium mix to a Perkin-Elmer DRC-e ICP-MS The laser wasoperated at a repetition rate of 10 Hz a power of 30 mWand spot size

ing magma at depth Influence on the eruptive activity of Somma-7013

Fig 1 a) Plot of clinopyroxene major element compositions within a portion of theCandashMgndashFe triangle White boxes represent the analyses performed in this work Forcomparison we reported also the compositions of Vesuvian magmatic clinopyroxenesanalyzed in literature (gray field Cioni et al 1998 Landi et al 1999 Marianelli et al1999 Cioni 2000Morgan et al 2004) and skarn clinopyroxene compositions (circlesGilg et al 2001) b) REE patterns of diopside clinopyroxene from Mt Vesuviuseruptions normalized to chondrite composition (Boynton 1984)

3L Dallai et al Earth and Planetary Science Letters 310 (2011) xxxndashxxx

of 40 μm Masses were acquired in peak hopping mode with a dwelltime of 10 ms Nist SRM 610 and 43Ca were adopted as external andinternal standards respectively Precision and accuracy were evalu-ated on the USGS-BCR-2 reference material and are estimated to bebetter than 5 and 10 relative respectively 2 to 3 analyses wereperformed for each crystal and the average values were considered

Oxygen isotope compositions of single mineral grains weremeasured at the CNR-IGG Pisa by conventional laser fluorination(Sharp 1995) reacting the samples under an F2 gas atmospherePurified oxygen gas was directly transferred into a Thermo FinniganDelta XP Isotope Ratio Mass Spectrometer via a 13A zeolite molecularsieve All the data are given following the standard δ-notation relativeto SMOW (Standard Mean Oceanic Water) Duplicate measurementswere performed when sufficient material was available and theaverage δ18O values were considered plusmn the standard error of themean In the course of analysis an in-house laboratory QMS quartzstandard (δ18O SMOW=1405permil) calibrated vs the internationalquartz standard NBS28 (δ18O=+958permil) was used yielding anaverage δ18O value=+1408permil (1 s=014 n=12) Standard NBS30(δ18O=+524permil) was also used during the study and gave an averagevalue of δ18O=522permil (1 s=016 n=7)

4 Results

41 Mineral chemistry

Olivine crystals from all the selected eruptions vary in a restrictedrange of composition (from Fo86 to Fo91) with the most primitivecrystals (Fo91) measured in samples collected from the AS2f eruption

Please cite this article as Dallai L et al Carbonate-derived CO2 purgiVesuvius Italy Earth Planet Sci Lett (2011) doi101016jepsl20110

(Table 1) Olivine has very low trace elements concentrations exceptfor highly compatible elements like Cr and Ni as expected for crystalsgrowing from basaltic melts

Pyroxene composition at SV is largely variable reflecting thecombined effect of complex processes of fractional crystallization andmagma mixing (Cioni et al 1998) In order to study crystalsrepresentative of the first phases of magma crystallization we alsoselected unzoned diopside crystals (En45ndash48 Fs4ndash9 Cioni et al 1998)Melt inclusions in diopside are in fact indicative of a very earlycrystallization both for their composition and for the high homo-geneization temperature measured (Cioni 2000 Cioni et al 1998Marianelli et al 1995) All the analyzed crystals are similarly LREE-enriched (Table 2 Fig 1) and show convex-upward REE patternstypical of diopside crystallized frommafic primitivemagma (eg Diohet al 2009 Ying et al 2006) The magmatic derivation of diopside isalso confirmed by their content in Wollastonite molecule lower thanthat typical of skarn material (Gilg et al 2001 Fig 1a)

An important issue of this study is related to the assumption that theselected olivinendashpyroxene pairs were in chemical equilibrium Meltinclusions hosted in olivine and diopside show similar homogeneouscompositions thereby implying that crystals are formed in the samekind of melt (Marianelli et al 1995) Moreover FendashMg partitionbetween olivine and diopside (Kdolcpx

FeMg) suggest a crystallizationtemperature around 1200 degC (based on the geothermometric relation-ship proposed by Loucks (1996)) in good agreement with thehomogenization temperature measured for melt inclusions (varyingbetween 1160 and 1200 degC Cioni et al 1998 Marianelli et al 1995)

42 Oxygen isotope composition

The δ18O values of the measured olivine from the differenteruptions at Mt Vesuvius vary from 55 to 71permil (Table 1 Fig 2a)and variability is narrower within a single eruption Olivine crystalsfrom Avellino and Pollena eruptions have the largest range (from 589to 711permil and 592 to 703permil respectively) while olivine crystals fromtheMiddle Age AS2f eruption vary from 604 to 652permil and those fromPompeii eruption from 551 to 619permil Overall no typical mantle δ18Ovalues (δ18Ool=518plusmn028permil Mattey et al 1994) were recoveredand olivine crystals from the Pompeii eruption show a few valuessimilar to the melts of island arc volcanics (Bindeman et al 2005)This is not unexpected considering the complex and recentsubduction-related volcanic history of Italian Quaternary lavas (egPeccerillo 1999) Mantle-like O-isotope compositions have beenrecovered only in a few monomineralic cumulates (Dallai et al 2004Peccerillo et al 2004) suggesting that slight mantle O-isotopevariability is overprinted significantly by processes that occurred inthe magma chamber(s) Also clinopyroxenes show δ18O values(Table 2 Fig 2b) varying over a narrow range (Avellino from 625to 677permil Pollena 655 to 690permil AS2f 648 to 698permil) with crystalsfrom Pompeii eruption showing slightly lower values (604 to 680permil)The highest δ18O values (three δ18O values above 71permil) are shown bydiopside crystals from the phono-tephritic portion (grey pomice) ofthe AD 79 Pompeii Pomice eruption Considering the mean values ofeach olivine and clinopyroxene population and their standarddeviations (stdevsqroot n_samples) the δ18O values of the largesteruptions (Avellino and Pompeii) do not overlap whereas those of thesmaller eruptions (Pollena and AS2f) vary in the same range (Fig 3)These data suggest that the near-primary melts from which theminerals crystallized possibly underwent variable contaminationduring the early stages of crystallization The fact that the Fo-richestolivine belongs to a small eruption and have high δ18O valuesindicates that the almost unevolvedmafic magmawasmodified for itsO-isotope composition by interaction with an 18O-enriched phaseThe variability measured in the isotopic composition contrasts withthe homogeneous major and trace elements composition of thephenocrysts With the exception of Avellino crystals the isotopic

ng magma at depth Influence on the eruptive activity of Somma-7013

Table 1Major elements compositions (wt) of olivine in studied eruptions For each analyzed crystal Fo (mol) and δ18O are presented

Major elements oxides wt

P5-o18 P5-o19 P5-o110 P5-o113 P5-o112 P5-o111 TR2-o12 TR2-o13 TR2-o14 TR2-o18

Mean St dev Mean St dev Mean St dev Mean St dev Mean St dev Mean St dev Mean St dev Mean St dev Mean St dev Mean St dev

SiO2 4032 023 4073 017 4066 018 4082 028 4036 043 4000 029 4055 016 4044 024 4033 039 4049 027TiO2 002 001 001 001 001 001 001 001 002 001 001 001 000 000 000 000 001 002 000 001Al2O3 002 001 002 001 002 001 002 001 002 001 002 001 003 001 002 002 002 001 001 001FeO 1280 012 1043 017 1217 008 1058 009 1266 009 1267 007 1033 012 1031 011 1038 008 1013 007MnO 023 002 017 002 020 001 020 000 022 003 022 001 018 001 018 001 018 001 018 001MgO 4741 024 4888 022 4750 011 4890 030 4726 028 4751 041 4920 018 4958 018 4912 016 4965 032CaO 028 001 029 001 030 001 029 000 030 001 030 002 030 001 029 001 029 001 028 001Na2O 001 001 001 001 003 001 003 002 002 001 002 001 001 001 001 000 000 001 001 001K2O 001 001 001 000 000 000 002 001 001 000 000 000 000 001 000 000 001 001 000 000Cr2O3 001 001 002 001 001 001 003 002 001 002 001 001 003 002 002 001 003 002 004 002NiO 015 002 022 003 016 001 020 002 017 002 015 001 020 002 020 002 022 001 021 001

Fo 8600 8900 8700 8800 8600 8600 8930 8940 8924 8957

Trace elements ppm

IsotopeLi 7 24885 2524 23495 2062 27705 2511 22015 2296Be 9 129 bdl 124 bdl bdl bdl 137 bdlB 11 398 3865 355 723 287 662 451 8735Sc 45 49415 42305 48185 46085 478 4919 4554 38715Ti 49 69755 6955 7533 6229 79775 7398 4253 64235V 51 1814 1363 1803 16345 17905 19285 16105 1447Cr 53 40562 1772205 679275 1781675 41664 491585 1854625 2130615Co 59 1489455 113244 1250925 1157495 1368735 1408625 1136185 117129Ni 60 1025691 1219926 1012671 1261338 959271 1006929 1265573 1340372Zn 66 65633 49312 54654 501555 58356 591075 470835 492545Rb 85 0434 bdl bdl bdl 0115 01015 0287 bdlSr 88 01485 bdl 0093 0105 0224 0152 0135 0145Y 89 0855 0566 0725 05295 088 064 03665 0358Zr 90 03325 034 041 02225 02995 044 045 057Nb 93 0179 0035 bdl 0039 0131 bdl 0078 bdlCs 133 bdl 0275 0078 0191 bdl bdl 01015 bdlBa 137 bdl 026 bdl bdl bdl 0126 056 031La 139 bdl bdl 014 0129 bdl 0045 bdl bdlCe 140 bdl bdl 0082 0917 bdl bdl 0023 0073Pr 141 bdl 003855 bdl bdl 0029 bdl bdl bdlNd 146 041 029 bdl 011 bdl 0095 bdlSm 149 bdl 0125 bdl 0131 bdl 039 0134 bdlEu 151 bdl bdl bdl 007 0033 bdl bdl bdlGd 157 bdl 029 bdl 0149 bdl 0138 bdl bdlTb 159 00465 bdl 0018 00285 0018 bdl 0019 bdlDy 163 0162 0075 0301 00835 01875 00775 bdl bdlHo 165 0067 0021 bdl bdl 00505 0066 0064 0075Er 167 053 bdl 035 009 048 02995 bdl bdlTm 169 0037 0068 bdl 0038 0034 bdl 002 0043Yb 173 035 bdl 032 036 044 033 029 bdlLu 175 bdl 002 0077 bdl 0073 0055 0145 0047Hf 177 bdl bdl 01835 bdl 0088 0094 bdl 022Ta 181 0025 bdl bdl 0025 0048 bdl 0054 0058Pb 208 026 027 044 bdl 04 003 034 036Th 232 bdl 0038 bdl 004 0038 bdl 0084 bdlU 238 bdl 00395 01065 bdl 0079 bdl bdl 00785

4 L Dallai et al Earth and Planetary Science Letters 310 (2011) xxxndashxxx

composition of clinopyroxene and olivine suggest isotopic equilibri-um between the two phases (δ18Odiopsidendasholivine=04permil Mattey et al1994) and their O-isotope fractionation defines a temperature of1240 degC (Chiba et al 1989) slightly higher than the temperature ofcrystallization based on petrologic inferences (Cioni et al 1999)

5 Discussion

Distinct initial O-isotope composition of Pompeii andor Avellinoand Pollena eruptions (Fig 2) and the different slopes of δ18OolndashFool co-variation trends (Fig 4) indicate that a high δ18O material (possiblycarbonate) interacted with different modalities or at a different degreewith the mafic melts According to the data on primary melts fromSouthern Italy Quaternary volcanism we can rule out that the δ18Ovalues measured on SV mafic crystals are representative of uncontami-

Please cite this article as Dallai L et al Carbonate-derived CO2 purgVesuvius Italy Earth Planet Sci Lett (2011) doi101016jepsl20110

nated primarymantle-derived compositions The Fo contents of olivinephenocrysts can be used to trace the chemical evolution of the maficmelts that fed the reservoirs involved in the studied eruptions

The δ18O values of these early crystallized phases could derivefrom the following type-mechanisms

ndash crystallization from a magma (slightly) contaminated by carbon-ate digestion

ndash crystallization fromanuncontaminatedmagma followedbydiffusivehigh temperature solid-state isotopic re-equilibration of the melt-crystals assemblage during successivemagmandashcarbonate interaction

The solid-state O-isotope diffusion coefficients for olivine andclinopyroxene are in the range of 10minus19 to b10minus21 (m2s) atmagmatic conditions (Connolly and Muehlenbachs 1988 Farver

ing magma at depth Influence on the eruptive activity of Somma-7013

1867 1507 18295 1951 2708272 bdl 436 273 bdl372 5095 768 455 69553135 3466 42745 50295 378454062 39645 56655 80715 521112235 13785 1373 2104 148451549035 162721 2095025 41317 208652844315 961805 1181155 1422715 1223751073974 1103032 1420223 1096706 1455602396625 418845 501925 66751 523505bdl bdl bdl bdl 0520134 0089 0177 0199 01630438 02755 0551 07 0479bdl 036 04655 044 026450077 bdl 0085 036 bdl0036 bdl 0019 003 bdl043 018 0159 bdl 02845

bdl bdl bdl bdl bdl 0028 015 bdl0025 0138 bdl 0155 bdlbdl 0037 bdl 0142 bdl0235 bdl 0116 04645 0220157 bdl bdl bdl 0370083 004 0078 0089 0074bdl 017 052 044 bdlbdl 0024 0022 0061 bdl02305 bdl bdl bdl 0076bdl 0087 0072 0023 bdlbdl 023 bdl 02165 bdl0045 0059 00545 004 bdlbdl bdl 039 bdl 021800565 bdl 0093 0038 0044bdl 0114 0228 bdl bdlbdl 0033 bdl 0027 bdl042 bdl bdl 144 bdlbdl bdl 0045 0072 bdlbdl bdl bdl bdl bdl bdl bdl bdl 068

Table 1Major elements compositions (wt) of olivine in studied eruptions For each analyzed crystal Fo (mol) and δ18O are presented

Major elements oxides wt

TR2-o17 TR2-o16 TR2-o15 P5-o11 P5-o12 P5-o13 P5-o16 P5-o15 P5-o14 TR2-o19 TR2-o110

Mean St dev Mean St dev Mean St dev Mean St dev Mean St dev Mean St dev Mean St dev Mean St dev Mean St dev Mean St dev Mean St dev

4034 036 4020 027 4095 0410 4023 020 4061 027 4028 011 4055 010 4030 021 4059 024 4060 036 3997 044000 000 001 001 001 001 000 000 001 001 001 001 001 001 001 001 001 001 001 0000 001 001001 000 001 001 002 000 001 001 001 001 003 000 001 001 002 000 001 001 002 000 001 000

1035 011 1264 010 1031 004 1491 007 1279 010 1339 014 1276 014 1297 016 1053 015 1044 002 1354 011019 003 021 002 018 000 028 000 022 003 023 001 022 001 023 001 019 002 019 002 024 002

4931 035 4761 038 4888 063 4562 060 4709 037 4657 024 4672 014 4686 033 4879 040 4895 037 4686 030029 001 029 001 030 001 020 001 029 001 028 001 029 001 029 000 030 001 030 001 027 001001 001 000 000 001 002 002 001 000 000 001 000 003 003 001 001 000 000 000 000 000 001000 000 000 000 000 000 003 001 001 001 001 000 001 001 000 000 000 000 001 001 001 000004 001 000 001 002 002 002 002 001 001 001 002 002 001 001 001 005 001 005 001 001 001023 001 015 001 020 002 016 001 015 001 016 002 016 002 015 002 020 003 023 004 017 002

8929 8685 8925 8400 8600 8500 8600 8600 8800 8914 8584

5L Dallai et al Earth and Planetary Science Letters 310 (2011) xxxndashxxx

2010 Ingrin et al 2001 Ryerson and McKeegan 1994) thereby thetime needed to equilibrate millimeter-size crystals is in the order of106 yrs 3 orders of magnitude larger than the assumed residence timeof early formed crystals (the average time-life for a magma chamberat SV is not longer than a few thousand years Morgan et al 2006Scaillet et al 2008) Accordingly we suggest that minerals crystal-lized within a primary magma that had been 18O-enriched before thatsignificant differentiation occurred Two main processes of magmandashcarbonate interaction could be able to produce a substantial increasein magma δ18O value

ndash bulk carbonate assimilation in the deep crustndash diffusive fluid-melt equilibration between a primarymagma and a

high-δ18O CO2 flux produced by decarbonation of the crustalbasement

Please cite this article as Dallai L et al Carbonate-derived CO2 purgiVesuvius Italy Earth Planet Sci Lett (2011) doi101016jepsl20110

Using simplemass balance calculations and assuming a δ18O valueof 551permil as least contaminated (primary) olivine atMt Vesuvius anda δ18O value of 25permil for average local meta-limestones and dolostone(Gilg et al 2001) the δ18O values measured in olivine andclinopyroxene (and hence in the tephritic and K-basaltic melts fromwhich they crystallized) would account for a variable carbonateassimilation between 6 and 8 Contamination of a mafic magma byvariable amounts (up to 20 wt) of sedimentary carbonate rocks hasbeen suggested to explain the different degree of silica under-saturation alkali enrichment and FeOMgO ratios in the differenti-ation from shoshonitic basalts to tephrites and to produce extremefoiditic (alkali-rich and silica-poor) compositions during shallow levelmagma crystallization (Freda et al 2008 Iacono Marziano et al2007 Mollo et al 2010) In these experimental runs the amounts ofcrystallized clinopyroxene and phlogopite increase proportionally

(continued on next page)

ng magma at depth Influence on the eruptive activity of Somma-7013

Table 1Major elements compositions (wt) of olivine in studied eruptions For each analyzed crystal Fo (mol) and δ18O are presented

Major elements oxides wt

TR2-o111 TR2-o115 TR2-o114 TR2-o116 TR2-o117 TR2-o118 TR2-o119 TR2-o120 TR2-o121

Mean St dev Mean St dev Mean St dev Mean St dev Mean St dev Mean St dev Mean St dev Mean St dev Mean St dev

SiO2 4041 040 4047 034 4063 020 4039 041 4063 018 4047 053 4007 026 4039 017 4061 027TiO2 000 000 000 001 001 002 001 001 001 001 002 001 000 000 001 001 001 001Al2O3 001 001 002 001 001 001 001 000 002 001 002 001 001 001 001 001 001 001FeO 1048 009 1008 012 1025 011 1214 014 1027 007 1015 006 1040 005 1260 008 1015 007MnO 018 002 019 001 019 002 021 002 019 002 017 002 018 001 022 001 018 001MgO 4933 027 4951 010 4908 017 4801 046 4959 019 4926 032 4938 048 4731 012 4948 028CaO 030 001 029 001 029 001 029 002 028 001 028 001 029 001 028 001 028 000Na2O 001 001 001 001 001 001 002 002 001 001 002 001 001 001 000 000 002 001K2O 001 000 001 000 001 000 000 000 001 000 001 001 000 001 001 001 001 000Cr2O3 004 003 004 002 003 001 002 001 003 001 003 002 002 001 001 001 003 001NiO 021 001 019 002 020 001 019 001 021 001 020 002 021 002 019 001 021 002

Fo 8919 8958 8934 8739 8942 8948 8927 8680 8952

Table 1 (continued)

6 L Dallai et al Earth and Planetary Science Letters 310 (2011) xxxndashxxx

with an increasing fraction of carbonate added to the starting meltand carbonate digestion proceeds in concert with clinopyroxenecrystallization according to the available MgO in the systemExperiments also show that hyaline glass with rare olivine crystalscan be produced only in CaCO3-free runs and moderate (5 wt)CaCO3 addition results in highly crystalline olivine-free products(Mollo et al 2010) It could be argued that olivine may still be a stablephase during early stages of Mg-rich carbonates (dolomitic lime-stones to dolomites) assimilation These latter crop out in theVesuvius area (eg Iacono-Marziano et al 2009) and could be aviable contaminant for Vesuvian magmas However dolomiteassimilation acts to increase the MgO activity in the melt therebyproducing high-Fo (N090 mol) low-Ni and high-18O olivinesassociated with clinopyroxenes which evolve toward Ca-Tschermakand esseneite components (Gaeta et al 2009 Peccerillo et al 2010)These features are not detected in SV mafic products discarding thehypothesis of an important bulk assimilation of Mg-rich carbonates atdepth

Experiments of carbonate contamination of Vesuvius melts areeven more stringent as they claim that at least 10ndash14 wt ofcarbonate assimilation is needed to pass from K-basaltic to tephriticcompositions (Iacono-Marziano et al 2009) In addition simple massbalance calculations based on O-isotope data constrain the maximumamount of carbonate assimilation able to explain the observed rangeof δ18O to about 7 by weight lower than that suggested by theresults of experimental petrology

Using the software Pele (a PC-hosted program to model thecrystallization of silicate liquids based on theMELTS algorithm able tohandle variable processes of carbonate assimilation Boudreau 1999)the effects of bulk carbonate assimilation on the chemical and isotopiccomposition of themagma can bemodeled Results of calculations canbe used to quantitatively constrain the amount of carbonateassimilation (Appendix 1 and Table 3) In particular the observedequilibrium mineral paragenesis of olivine and diopside is notconsistent with substantial limestonedolomite assimilation whichpredicts early olivine resorption (olivine is present as a crystallizingphase only for assimilation of less than 5 of carbonate) similar towhat is shown by the experiments (Fig 5) Massive (higher than 10by weight) assimilation of carbonate rock by a K-trachybasalt wouldalso result in an important increase of CaO accompanied by a decreaseof the SiO2 and MgO content of the contaminated magma up toconcentrations never recorded in natural mafic samples (respectivelyhigher than 155 and lower than 45 and 47 see Appendix 1)

Another problematic aspect of magmandashcarbonate assimilation isrelated to the thermal budget of the process Thermodynamicalconstraints on the process of magmandashcarbonate assimilation calcu-lated using the EC-RAFC worksheet (Bohrson and Spera 2003 Spera

Please cite this article as Dallai L et al Carbonate-derived CO2 purgVesuvius Italy Earth Planet Sci Lett (2011) doi101016jepsl20110

and Bohrson 2001 and references therein) predict that starting froma trachybasaltic melt at 1200 degC (a good highly conservativeapproximation for the liquid temperature) 10 wt carbonate assim-ilation would decrease the initial magma temperature by at least100 degC (Fig 6) which contrasts with the temperature of crystalliza-tion measured for both olivine and diopside-hosted melt inclusions(Cioni et al 1998) Parameters used in the modeling are listed inTable 3 while magma and carbonate thermodynamical propertiesused in the calculations are derived from Bohrson and Spera (2003)Haynes (2010) Lvov (2002) and Wyllie and Boettcher (1969)However it should be noted that that carbonate assimilation insilicate melt may occur via rapid decomposition and degassing of CO2

rather than full-scale melting (Deegan et al 2010) thereby implyingthat the amount of energy required may be different (lower) thanpredicted by EC-RAFC models and that the amount of assimilationmay be underestimated by model calculations On the other hand theconsistent δ18O values of olivine and clinopyroxene measured at SVsuggest a homogeneous process of magma contamination This wouldbe hardly achieved by small degrees of carbonate dissolution likelyresulting into local hyper-calcic melt pockets It is likely that intra-melt homogenization occurs as higher proportions of carbonate aredigesteddissolved the latter driving melt composition towards moreevolved compositions

Therefore on the basis of the 1) occurrence of large olivinephenocrysts implying olivine stability in the magma in spite of phaseresorption which is expected from carbonate assimilation 2) nearprimary chemical composition of the clinopyroxene showing nosignificant increase in Ca-Tschermak and esseneite components3) thermodynamic issues related and energy-constrained modelcalculations we consider bulk assimilation as an unlikely process toproduce the δ18O values measured in these crystals and we favor aprocess of CO2 fluxing through the melt at depth

6 The effects of CO2 flux over the δ18O of primary magmas

As an inevitable consequence of interaction between magma andsedimentary carbonate large amounts of 18O-rich (sedimentary-derived) CO2 are released from the carbonates Because CO2 is anoxygen-rich carrier and fluid-melt oxygen diffusion is enhanced atmagmatic temperature this flux may diffuse through the magma andeventually re-equilibrate its isotopic composition without inducingother significant compositional changes Experimental data for O-isotope equilibrium between CO2 andmelilite basalt and silica glassespredict δ18O values of CO2 at magmatic conditions in the range of 2ndash25permil higher than coexisting glass (Appora et al 2003 Matthewset al 1998) Due to the high self-diffusion coefficients of oxygen inbasaltic melts (in the range of 10minus7 to 10minus8 cm2 sminus1 Muehlenbachs

ing magma at depth Influence on the eruptive activity of Somma-7013

Table 2Major (wt) and trace (ppm) elements composition of pyroxenes from the studied eruptions Mean=averaged composition from 2ndash3 point analyses on the same crystalStdev=standard deviation bdl=below detection limit

Major elementsoxides wt

Avellino Pompei

Sample AV93-47-px1 AV93-47-px2 AV93-47-px3 AV93-47-px4 AV93-46-px1 TR2-px1 TR2-px2 TR2-px3 TR2-px4 TR2-px5

Mean St dev Mean St dev Mean St dev Mean St dev Mean St dev Mean St dev Mean St dev Mean St dev Mean St dev Mean St dev

SiO2 5286 055 5351 032 5295 048 5338 037 5375 042 5579 029 4761 1612 5438 045 5264 017 5504 044TiO2 040 009 030 002 037 006 033 004 034 005 023 000 041 007 036 003 038 001 026 009Al2O3 252 068 169 009 218 036 180 028 212 033 130 004 178 056 178 015 174 019 153 026FeO 445 039 361 011 396 035 385 005 371 023 281 005 364 024 334 015 352 023 299 046MnO 010 002 009 001 008 002 009 001 009 001 008 001 010 001 008 001 008 001 008 002MgO 1627 057 1697 005 1653 034 1701 039 1700 012 1678 006 1365 163 1647 006 1726 024 1668 039CaO 2346 019 2350 009 2346 013 2319 014 2313 035 2322 012 2150 359 2323 024 2345 017 2285 020Na2O 012 002 011 001 012 002 012 002 014 003 016 002 010 002 015 001 015 001 016 002K2O 000 000 000 001 000 000 000 000 001 001 000 000 000 000 001 000 000 000 001 001Cr2O3 013 004 014 005 018 012 012 002 037 005 052 014 010 012 030 004 015 007 058 032NiO 003 002 002 002 004 001 001 002 003 002 003 002 002 001 002 001 003 001 003 002

Wo 4725 065 4699 008 4727 016 4645 055 4650 070 4757 013 4934 185 4758 026 4664 011 4715 055En 4559 128 4722 018 4636 074 4739 065 4754 034 4782 016 4384 088 4695 013 4776 040 4789 089Fs 716 065 579 016 636 061 616 012 596 036 462 008 682 109 547 025 559 037 495 077

Trace elements ppmLi 7 062 06 037 0615 bdl 0835 0675 056 074 0795 bdl 095 051 092Be 9 038 083 bdl 095 bdl 086 021 0475 027 028 bdl 069 153 9 bdlB 11 0765 104 143 146 bdl 144 bdl 101 164 148 bdl bdl bdl 11 129Sc 45 107585 88305 90445 95485 8748 60895 9265 90565 85935 7207 9658 9363 94165 45 8949Ti 49 26797275 1626325 2189095 191773 19475 132555 219823 206823 2040775 17881 2388305 268662 2443405 49 253088V 51 194795 125435 16373 141165 11211 62295 116765 102935 109205 10546 12099 9525 12812 51 157015Cr 53 6262075 105362 75761 91328 269153 3529675 864535 1912875 1018085 2393295 9846 989315 642165 53 11209Co 59 324725 2727 3152 2939 22555 23915 2603 26285 26045 2481 22965 2272 28285 59 2568NI 60 1259725 13469 13507 12961 14259 205395 144805 164555 16114 184205 8335 117665 1306 60 86595Zn 66 1407 1102 1476 1388 11845 1106 1292 1309 1201 12065 10215 13305 13665 66 16855Rb 85 0031 0027 bdl 0074 0067 bdl 0124 bdl 0067 bdl bdl 0429 bdl 85 0157Sr 88 790525 65625 844 68355 78475 86355 9445 953 8383 8138 8424 99865 88005 88 95765Y 89 924 567 7815 714 777 423 656 6885 556 603 647 8575 6605 89 8515Zr 90 1577 697 1405 8915 907 463 14355 114 888 8995 9195 1478 1264 90 1495Nb 93 00725 00183 00405 00272 0078 00302 0026 00371 0035 00395 00385 0091 002015 93 0108Cs 133 00089 bdl 001845 bdl bdl bdl bdl bdl bdl 00035 bdl 0026 00109 133 0069Ba 137 0132 00995 0163 0132 0126 bdl 0621 01635 0109 02755 bdl 075 0052 137 058La 139 248375 13085 21215 1793 2 2146 264 371 18365 1853 177 365 242 139 2835Ce 140 0625 534 897 6775 714 718 1069 12445 734 7415 59 11375 9685 140 11545Pr 141 189375 10295 16665 1385 143 1329 1878 21575 1538 14795 1375 204 1736 141 1835Nd 146 116625 658 1018 884 868 6675 10525 11865 9 8665 772 11745 9945 146 11245Sm 149 407 2155 3505 28 2455 2235 2785 3275 28 289 2235 326 2775 149 3125Eu 151 092875 0558 08265 08175 069 0559 06925 08465 06745 0754 06715 0865 08315 151 0765Gd 157 343 203 292 2595 2155 159 2835 255 222 2335 236 306 2785 157 266Tb 159 042325 0226 03755 0298 0365 0189 0304 03465 0297 03015 0239 0362 031 159 0326Dy 163 2265 1325 2205 1885 135 1175 1575 1845 13245 171 142 199 159 163 1715Ho 165 03445 0262 0339 0303 0232 01875 03015 0292 02415 024 02175 03545 0265 165 03205Er 167 0846 0347 07955 06975 0675 04545 0634 05275 05415 0672 0571 0885 06045 167 0795Tm 169 008925 00735 00675 0069 0077 00476 006105 00945 007 007175 0092 00905 00845 169 0101Yb 173 064125 03545 0487 0575 0395 0139 04905 05775 0251 05225 0305 039 0576 173 03865Lu 175 0101 005665 00622 005335 0081 00281 005805 00496 005305 00664 0052 00261 0069 175 006355Hf 177 0752 0393 0727 03995 0545 0212 08845 07125 04865 04625 0451 061 0607 111 0535Ta 181 00126 bdl 00083 bdl bdl 00037 001095 000905 0006 bdl 00178 00185 181 0049Pb 208 01565 01385 22675 02055 0059 0141 02525 01255 0231 0365 01735 0201 0253 208 03315Th 232 001835 00076 00432 003015 0056 0034 00512 0047 0055 0037 0047 00565 0034 232 01255U 238 001835 00235 00139 0078 00087 00111 00192 00363 bdl 00062 00201 0047 001915 238 0013

(continued on next page)

7L Dallai et al Earth and Planetary Science Letters 310 (2011) xxxndashxxx

and Kushiro 1974 Stolper and Epstein 1991) isotopic equilibrium isachieved in hours to days in the case of high molar oxygen ratiosbetween gas and melt (103 to 105) Conversely the silicate fractionwill change negligibly if the ratio between CO2 and melt is low andthe extent of oxygen isotope fractionation is recorded in the δ18Ovalue of CO2 (Stolper and Epstein 1991)

The SV complex characterizedby theoccurrence of a thick carbonatebasement represents an ideal site for thermally-induced CO2 produc-tion (Iacono-Marziano et al 2009 Fig 7) although a deeper source ofnon-volcanic CO2 (Frezzotti et al 2009) cannot be ruled out It followsthat olivine and diopside phenocrysts may have crystallized from

Please cite this article as Dallai L et al Carbonate-derived CO2 purgiVesuvius Italy Earth Planet Sci Lett (2011) doi101016jepsl20110

magmabodies stalling in deep (more than 8ndash10 km) reservoirswithin aCO2-degassing carbonate basement as hypothesized on the basis ofseismic tomography (Auger et al 2001 De Natale et al 2006) andexperimental petrology (Scaillet et al 2008) Oxygen isotopic re-equilibration between the magma and CO2 flux occurred at a pressurenot lower than 200 MPa (thepressure estimated fromvolatilemeasureson melt inclusions hosted in olivine and diopside after Marianelli et al2005) suggesting that CO2 was derived from decarbonation of thedeeper portion of the carbonatic basement In this case the process ofCO2 production could be considered as a general effect related to deepmagma generation transfer and intrusion possibly unrelated to the

ng magma at depth Influence on the eruptive activity of Somma-7013

Table 2Major (wt) and trace (ppm) elements composition of pyroxenes from the studied eruptions Mean=averaged composition from 2ndash3 point analyses on the same crystalStdev=standard deviation bdl=below detection limit

Major elementsoxides wt

Pompei Pollena

Sample P4-px4 P4-px5 P4-px7 VS98-539-px1 VS98-539-px2 VS98-539-px3 Scoria Fdf-px1 VS98543-px1 VS98543-px2 VS98543-px3

Mean St dev Mean St dev Mean St dev Mean St dev Mean St dev Mean St dev Mean St dev Mean St dev Mean St dev Mean St dev

SiO2 5279 052 5227 018 5186 041 5322 021 4981 318 5267 084 5297 016 5221 017 5350 023 5361 021TiO2 039 004 043 003 045 004 043 002 059 051 051 012 040 002 046 002 032 003 026 005Al2O3 175 024 195 021 194 016 274 019 293 284 244 062 212 009 226 008 175 037 132 015FeO 362 021 378 024 384 030 422 007 453 266 389 039 369 008 364 009 345 053 293 020MnO 007 002 009 001 009 001 009 002 010 007 008 002 009 002 010 003 009 001 007 001MgO 1746 031 1710 028 1717 029 1592 008 1505 288 1649 042 1678 011 1716 010 1699 048 1749 009CaO 2386 006 2387 017 2373 017 2358 004 2189 034 2385 023 2369 010 2321 011 2317 018 2329 014Na2O 013 002 017 001 015 002 017 002 021 014 013 001 013 002 017 001 015 008 016 001K2O 000 000 001 000 001 000 000 000 000 000 000 001 001 001 000 001 000 000 000 000Cr2O3 001 003 017 009 009 007 001 001 004 003 014 004 039 012 026 004 029 013 039 010NiO 001 001 002 000 003 001

Wo 4676 026 4708 036 4682 038 4802 007 4718 166 4780 011 4739 011 4642 015 4674 043 4661 009En 4760 061 4695 067 4713 068 4513 019 4486 686 4599 073 4671 013 4775 020 4768 109 4871 035Fs 565 036 597 039 606 049 686 013 797 521 621 065 591 013 583 018 557 087 468 029

Trace elements ppmLi 0615 1955 0945 103 229 327 3065 bdl 074 104 111 142 bdl 0945 114 041 bdlBe 095 073 135 052 067 067 079 073 1205 bdl 126 1185 121 bdl 147 063 069B 146 175 247 113 l62 162 135 195 109 bdl 1555 bdl bdl 23 114 188Sc 95485 80795 1003 87305 96615 8316 614 10802 9315 85625 69065 6893 84715 10334 8176 8806 71675Ti 191773 219807 34512 2059 248559 218134 159479 273764 280761 25392 17254 211828 22331 276879 202985 186779 147115V 141165 90235 13352 10746 104885 9958 6136 10292 6351 98685 57055 1105 7002 93585 67975 6086 71415Cr 91328 24946 7634 214032 13677 126487 273692 194294 113496 92448 45894 708943 30574 226808 207844 163798 57544Co 2939 21505 2473 2179 232575 2276 22185 2248 2123 2326 1867 286233 1857 2192 1824 20155 19455NI 12961 97065 12127 137695 131253 123255 15828 138805 139465 14571 15116 111073 1513 143645 12446 11192 167055Zn 1388 1113 12675 13375 1328 15095 16705 143 12115 1209 8765 18 9085 996 825 988 1148Rb 0074 0125 bdl bdl 057 057 bdl 0056 bdl 0165 0256 032767 bdl 0045 bdl 0065 0116Sr 68355 100125 87735 12221 11153 109575 90675 116485 205955 11943 95545 105953 90435 8722 85155 89645 9625Y 714 7215 8865 9975 878 7725 494 9685 10285 825 4255 809667 576 7785 578 6595 571Zr 8915 1095 2149 1549 16355 1154 458 19205 3332 15245 69 826 1312 1848 11385 8945 619Nb 00272 001955 0035 003515 007005 0117 bdl 0112 00635 0128 00285 013067 00201 00224 0024 0033 00111Cs bdl bdl bdl bdl bdl bdl 00252 bdl 0026 bdl bdl 006233 bdl bdl 0037 bdl bdlBa 0132 06245 035 0209 0299 0395 0225 041 0216 0621 02065 306 02435 0288 0214 051 0325La 1793 236 2475 4305 37725 3035 2015 419 638 348 151 252 217 258 212 1905 255Ce 6775 824 9255 14335 123875 10085 5875 13375 20035 1194 519 788333 6515 829 6635 6165 811Pr 1385 17 205 3195 236 1885 1165 267 3765 236 1205 179333 145 192 126 1455 173Nd 884 9445 11725 1597 125475 10975 5935 1564 21405 1457 6515 1021 8155 1072 8685 8775 1101Sm 28 242 4005 4785 36525 297 175 4305 504 392 206 315667 2635 295 218 293 2985Eu 08175 082 1105 1275 09775 091 0456 103 141 1005 0585 082033 0684 087 0574 075 079Gd 2595 254 355 416 3025 2815 1285 3245 4535 3915 1575 242667 211 2635 196 262 2785Tb 0298 03675 0367 0513 03955 0336 0222 0435 0535 045 0219 037333 0292 0344 0264 03085 02935Dy 1885 1805 2435 242 215 1785 097 2205 254 1565 121 166667 1165 1755 123 1475 1355Ho 0303 0187 03125 03205 028 0225 01455 03345 0377 02925 01715 023433 0207 0282 01875 0254 02205Er 06975 053 085 0765 070825 06515 0475 0825 094 087 03275 049733 059 074 04395 0466 04895Tm 0069 005055 00885 0085 008775 0092 0048 00555 01185 0076 00393 007833 00253 0084 004235 0048 00465Yb 0575 04 0553 0263 0381 03485 027 0605 051 066 0223 042833 04305 03395 02595 0276 03455Lu 005335 00515 0071 0034 00705 006 002325 0081 0081 00815 0047 005367 00535 00735 003165 00368 0037Hf 03995 0615 0955 0785 07075 047 0228 0895 1255 083 0372 0274 0705 0905 047 0495 0302Ta bdl 00188 bdl 000975 002435 00177 bdl 0021 0032 00098 00123 001283 00161 bdl 00074 bdl 00171Pb 02055 02515 0318 02685 026125 03485 0141 01765 01625 052 0136 0369 0129 01405 01475 0318 0155Th 003015 00174 00915 0078 006958 0086 004 0087 0089 0049 0033 003475 0044 00336 00635 bdl 00238U 0078 bdl 00157 00112 00392 00134 bdl 00095 bdl 00135 00154 00273 bdl 001045 011 0023 00155

Table 2 (continued)

8 L Dallai et al Earth and Planetary Science Letters 310 (2011) xxxndashxxx

specific volume of magma undergoing the flux and inducing nosignificant thermalcompositional changes on it The amount ofavailable carbonate is high whether compared with the volume ofinteracting magma and large amounts of CO2 could be continuouslyavailable through time Conversely an effect of thermal insulation ofcarbonates from the magma could be more effective in the shallowerreservoirs where magma can reside for a long time (hundreds tothousands of years) differentiate and directly interact with the hostingcarbonates partially digesting them in some cases

At Mt Vesuvius present-day CO2 flux (300 tday Iacono-Marzianoet al 2009 and references therein) has δ18O values varying between

Please cite this article as Dallai L et al Carbonate-derived CO2 purgVesuvius Italy Earth Planet Sci Lett (2011) doi101016jepsl20110

+23 and +28permil (Chiodini et al 2000) typical of CO2 degassed from acarbonate basement (Fig 7a) Average magma supply during the last4 ka of activity at SV has been estimated at 27ndash112 109 kgyr(Scandone et al 2008) If the present-day CO2 flux (11 108 kgyr) canbe extrapolated to the past the influence of such a flux to the supply ofmantle-derived magma can be calculated The result is that the ratio ofCO2-derived vs magma-derived oxygen is in the range 002ndash008 wt(Fig 7b) Assuming a δ18O for limestone-derived CO2 of 28permil thecalculated δ18O increase of 05 to 18permil matches the measured data forthe high-δ18O forsteritic olivine Considering the magma-CO2 gassystem as a whole in a single frame of time the increase of δ18O in

ing magma at depth Influence on the eruptive activity of Somma-7013

Table 2Major (wt) and trace (ppm) elements composition of pyroxenes from the studied eruptions Mean=averaged composition from 2ndash3 point analyses on the same crystalStdev=standard deviation bdl=below detection limit

Pollena 718

VS98543-px4 VS98543-px5 VS98543-px6 VS97718-pxl VS97718-px2 VS97718-px3 VS97718-px4 VS97718-px5 VS97718-px6 VS97718-px7

Mean Stdev Mean Stdev Mean Stdev Mean Stdev Mean Stdev Mean Stdev Mean Stdev Mean Stdev Mean Stdev Mean Stdev

5374 037 5317 084 5558 040 5240 049 5378 031 5355 059 5342 093 5416 037 5394 227 5176 259039 003 045 007 044 003 030 002 031 004 035 002 047 002 034 001 031 001 022 003208 021 201 044 240 038 133 020 098 022 154 022 198 006 135 004 101 004 145 027342 017 332 020 375 046 262 012 348 122 280 006 338 015 285 008 298 008 281 013008 001 008 001 009 000 005 001 010 004 006 002 007 001 007 002 008 001 007 001

1657 009 1651 035 1419 040 1774 026 1746 052 1750 085 1683 027 1712 009 1660 102 1684 0592304 019 2388 012 2306 010 2352 027 2338 039 2363 026 2328 017 2368 008 2296 032 2276 044014 001 016 002 013 001 014 002 012 004 014 002 013 001 011 002 010 001 014 001000 000 000 000 000 000 001 000 000 000 001 001 000 000 000 000 002 001 001 000031 005 018 008 010 001 081 020 024 028 065 022 044 003 043 003 029 004 075 020

002 001 002 001 003 001 003 003 004 002 002 001 002 002

4719 027 4824 030 5035 030 4677 046 4632 070 4709 111 4713 057 4758 014 4743 141 4699 0914722 024 4640 063 4310 106 4908 053 4814 128 4847 118 4741 046 4786 026 4764 161 4837 096559 028 536 037 654 082 415 022 554 195 444 012 546 021 457 013 493 024 464 030

0

5

10

15

20

50 55 60 65 70 75 800

2

4

6

8

10

57 60 63 66 69 72 75 78 81

Pompeii PAS2f

Avellino PPollena

Num

ber

18O18O

OLIVINE CLINOPYROXENE

a b

Fig 2 Histograms showing the variation of the δ18O values in olivine and clinopyroxene from the investigated eruptions

52 56 60 64 68 7256

60

64

68

72

7618O (permil)cpx

18δ

δ

O (permil)ol

permil40= O18

AS2f

Pompeii

Avellino

Pollena

Fig 3 The δndashδ plot correlating the average δ18O values of olivine and clinopyroxene fromeach volcanic eruption Sample bars refer to the standard deviation of each samplepopulation (stdevsqroot n_samples) Symbols are the same of Fig 1 For Pompeii andPollena eruptions the two δ18O values correspond to the averages of two distinct samples

Fig 4 The δ18Ool vs Fool negative co-variation trends in the four investigated eruptionsOlivine crystals from all the selected eruptions vary in a restricted range of chemicalcomposition (from Fo86 to Fo91) with the most primitive crystals (Fo91) measured insamples collected from the AS2f eruption Fo is the olivine composition calculated as[Mg(Mg+Fe)] Symbols are the same of Fig 1

Table 2 (continued)

9L Dallai et al Earth and Planetary Science Letters 310 (2011) xxxndashxxx

Please cite this article as Dallai L et al Carbonate-derived CO2 purging magma at depth Influence on the eruptive activity of Somma-Vesuvius Italy Earth Planet Sci Lett (2011) doi101016jepsl201107013

Table 3Parameters used in the EC-RAFC model calculation

tlm 1200 degC Liquidus T magmatmo 1200 degC Initial T magmacpm 1484 Jkg K Specific heat of magmacpa 1170 Jkg K Specific heat of assimilantcpr 1484 Jkg K Specific heat of recharge magmahm 396000 Jkg Enthalpy of crystallization of magmaha 360000 Jkg Enthalpy of melting of assimilanthr 396000 Jkg Enthalpy of crystallization of recharge magma

551 18O16O in magma25 18O16O in assimilant

4

6

8

10

12

14

16

18

20

22

70000 80000 90000 100000 110000 120000 130000Tmagma (degC)

18O

a

bcd

b1

Curve Tla Ta0 Ts Teq Ma0

b

a 900 800 850 900 177b 900 600 850 900 118

900 600 850 852 308c 700 600 650 700 241d 650 500 620 650 228

Fig 6 Figure shows the variation of isotopic composition of the magma during theprocess of assimilation as a function of magma temperature modeled by EC-RAFC(Bohrson and Spera 2001) Parameters used in themodeling are listed in Table 3 Ta0=assimilant initial temperature Tla = liquidus temperature Ts = solidus temperaturesTeq = equilibration temperature The grey box shows the range of δ18O values ofdiopside and olivine

10 L Dallai et al Earth and Planetary Science Letters 310 (2011) xxxndashxxx

Mt Vesuvius mafic melts can be modeled by using a simple mass-balance calculation in terms of CO2 flux assuming a fractionation factorsimilar to that of CO2-melilite melt (Appora et al 2003) Mass balancecalculation requires

xCO2δ18Oi

CO2 thorn eth1minusxCO2THORNδ18Oiglass frac14 xCO2

δ18OfCO2

thorn eth1minusxCO2THORNδ18Ofglass

with s=solid phase ol=olivinem=melt cpx=clinopyroxene g=gas phase i = initial f = final

The amount of CO2 (xCO2) required to produce the measured shiftοf δ18O from typical mantle values is in the range of 3ndash5permil that iscompatible with the estimated ratio of magma supply to CO2 flux

7 Implications on eruptive activity

The variability observed for the δ18O values of mafic magmas at SVis compatible with a sustained flux of carbonate-derived CO2 throughthe magma at PT conditions in equilibrium with the crystallization ofthe olivine and clinopyroxene assemblage The outcome of thisconclusion is that CO2 fluxing through magma may play a significantrole in the magmatic processes at SV In particular due to its limitedsolubility in magmatic melts at crustal pressures externally producedCO2 tends to concentrate into the fluid phase in equilibrium with themagmatic melt Several effects are possible

1) forced exsolution of water from previously undersaturatedmelt This effect can be very important as CO2 fluxing throughout themagma induces a decrease in the fugacity of the other volatile species(essentially H2O) in the fluid phase and a corresponding decrease in

1200

Temperature (degC)

GasCpxOl

10 CaCO -CaMg(CO3)2 assimilation 3

11201140116011801200

5 CaCO assimilation3

CpxGas

Wt

Wt

0

10

20

30

40

50

10

20

30

40

0

Fig 5 Diagrams of the modeled (Pele Boudreau 1999) mineral phase abundance during a pshow that in a process of carbonate assimilation olivine is stable only after assimilation ofmelts Initial magma temperature 1200 degC initial carbonate temperature 600 degC Initial liqui(Tf) corresponds to eruptive temperature of typical vesuvian magma calculated by Cioni et al

Please cite this article as Dallai L et al Carbonate-derived CO2 purgVesuvius Italy Earth Planet Sci Lett (2011) doi101016jepsl20110

their solubility in the magma (Dixon and Stolper 1995 Papale 1999)This process may promote the exsolution of H2O from the otherwiseundersaturated magma possibly enhancing the ability of the magmaitself to erupt explosively This appears particularly important in thecase of nearly volatile-saturated small mafic magma bodies Lookingat the recent activity of SV this effect could have been very importantespecially in the last 1500 yrs characterized by very frequenteruptions of small magnitude and intensity (Cioni et al 2008)

2) Overall decrease of the density of a shallow residing magmadue to the introduction of a poorly soluble volatile component likeCO2 which could force magma rise by increasing its buoyancy Asimilar mechanism has been proposed to explain explosive eruptionsof mafic magmas at the Alban Hills Volcano (Freda et al 2010)

3) If released during local assimilation of the carbonate host rocksin the shallow level magma chamber CO2 may have different effectsaccording to the size and shape of the reservoir In fact the ratiobetween the volume of the magma and that of the host rocks thatexchange heat and mass with the magma (the thermo-metamorphicandmetasomatic carapace) is low for small magma chambers The net

Temperature (degC)

GasCpxMt-Usp

10 CaCO3 assimilation

10 CaMgCO assimilation3

1120114011601180 1100

GasCpxOl

Wt

Wt

0

10

20

30

40

50

10

20

30

40

0

rocess of carbonate assimilation and equilibrium crystallization The different diagramsN10 wt of dolomite All these experiments produce strongly undersaturated residuald and assimilant from Cioni et al (2008) Santacroce et al (2008) The final temperature (1998) Olivine (Fo=8664) is a stable phase only for simulations without assimilation

ing magma at depth Influence on the eruptive activity of Somma-7013

Fig 7 a) Schematic illustration of the mechanism of magmacarbonate interaction at Mt Vesuvius b) Graphical representation of the δ18O shift as a function of CO2magma ratio(wt) based on simple mass-balance calculation Figure is not at scale

11L Dallai et al Earth and Planetary Science Letters 310 (2011) xxxndashxxx

result is that smaller is the magma reservoir larger is the ratiobetween the mass of carbonate-derived CO2 and magma thus a largechange in the total CO2 fugacity (and consequently H2O solubility) canbe imposed on a small magma batch An important corollary is thatthe ldquoaptituderdquo to erupt explosively of the small mafic magma bodiesthat established at shallow level in the SV area may have been largelyincreased by local processes of magmandashcarbonate interaction

We conclude that the O-isotope compositions of the ldquobasalticrdquomelts at Vesuvius were derived from an early process of CO2 fluxingfrom the carbonate basement at the roots of the volcanic structureThis process had the potential to increase the intrinsic explosivity ofthe mafic magmas feeding the magma chamber Additional bulklimestone assimilation occurred at shallow depths and mainlyinvolved partially differentiated melts

Supplementarymaterials related to this article can be found onlineat doi101016jepsl201107013

Acknowledgments

The manuscript was improved by constructive reviews by FrancesM Deegan and an anonymous reviewer

References

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Auger E Gasparini P Virieux J Zollo A 2001 Seismic evidence of an extendedmagmatic sill under Mt VesuviusScience 294 1510ndash1512

Ayuso RA De Vivo B Rolandi G Seal II RR Paone A 1998 Geochemical andisotopic (NdndashPbndashSrndashO) variations bearing on the genesis of volcanic rocks fromVesuvius ItalyJ Volcanol Geotherm Res 82 (1ndash4) 53ndash78

Please cite this article as Dallai L et al Carbonate-derived CO2 purgiVesuvius Italy Earth Planet Sci Lett (2011) doi101016jepsl20110

Baker CK Black PM 1980 Assimilation and metamorphism at basalt-limestonecontact Tokatoka New ZealandMineral Mag 43 797ndash807

Barberi F Leoni L 1980 Metamorphic carbonate ejecta from Vesuvius plinianeruptions evidence of the occurrence of shallow magma chambersBull Volcanol43 107ndash120

Barnes C Prestvik T Sundvoll B Surratt D 2005 Pervasive assimilation of carbonateand silicate rocks in the Hortavaer igneous complex north-central NorwayLithos80 179ndash199

Bindeman IN Eiler JM Yogodzinski GM Tatsumi Y Stern CR Grove TLPortnyagin M Hoernle K Danyushevsky LV 2005 Oxygen isotope evidence forslab melting in modern and ancient subduction zonesEarth Planet Sci Lett 235480ndash496

Bohrson WA Spera FJ 2001 Energy-constrained open system magmatic processes IIapplication of energy-constrained assimilation-fractional crystallization (EC-AFC)model to magmatic systemsJ Petrol 42 1019ndash1041

Bohrson WA Spera FJ 2003 Energy-constrained open-system magmatic processesIV geochemical thermal and mass consequences of energy-constrained rechargeassimilation and fractional crystallization (EC-RAFC)Geochem Geophys Geosyst 4(2) 8002 doi1010292002GC000316

Boudreau AE 1999 PELE mdash a version of the MELTS software program for the PCplatformComput Geosci 25 201ndash203

Boynton WV 1984 Geochemistry of the rare earth elements meteorite studiesInHenderson P (Ed) Rare Earth Element Geochemistry Elsevier pp 63ndash114

Brocchini D Principe C Castradori D Laurenzi MA Gorla L 2001 Quaternaryevolution of the southern sector of the Campanian Plain and early Somma-Vesuviusactivity insights from the Trecase 1 wellMineral Petrol 73 67ndash91

Chadwick JP Troll VR Ginibre C Morgan D Gertisser R Waight TE DavidsonJP 2007 Carbonate assimilation at Merapi volcano Java Indonesia insights fromcrystal isotope stratigraphyJ Petrol 48 1793ndash1812

Chiba H Chacko T Clayton RN Goldsmith JR 1989 Oxygen isotope fractionationsinvolving diopside forsterite magnetite and calcite application to geothermome-tryGeochim Cosmochim Acta 53 2985ndash2995

Chiodini G Allard P Caliro S Parello F 2000 18O exchange between steam andcarbon dioxide in volcanic and hydrothermal gases implications for the source ofwaterGeochim Cosmochim Acta 64 2479ndash2488

Cioni R 2000 Volatile content and degassing processes in the AD 79 magma chamberat Vesuvius (Italy)Contrib Mineral Petrol 140 40ndash54

Cioni R Civetta L Marianelli P Metrich N Santacroce R Sbrana A 1995Compositional layering and syn-eruptive mixing of a periodically recentlled shallowmagma chamber the AD 79 Plinian eruption of VesuviusJ Petrol 36 739ndash776

ng magma at depth Influence on the eruptive activity of Somma-7013

12 L Dallai et al Earth and Planetary Science Letters 310 (2011) xxxndashxxx

Cioni R Marianelli P Santacroce R 1998 Thermal and compositional evolution ofthe shallow magma chambers of Vesuvius evidence from pyroxene phenocrystsand melt inclusionsJ Geophys Res 103 18277ndash18294

Cioni R Marianelli P Santacroce R 1999 Temperature of Vesuvius magmasGeology27 443ndash446

Cioni R Bertagnini A Santacroce R Andronico D 2008 Explosive activity anderuption scenarios at Somma-Vesuvius (Italy) towards a new classificationschemeJ Volcanol Geotherm Res 178 331ndash346

Civetta L DrsquoAntonio M de Lorenzo S Di Renzo V Gasparini P 2004 Thermal andgeochemical constraints on the lsquodeeprsquo magmatic structure of Mt Vesuvius JVolcanol Geotherm Res 133 1ndash12

Connolly C Muehlenbachs K 1988 Contrasting oxygen diffusion in nephelinediopside and other silicates and their relevance to isotopic systematics inmeteoritesGeochim Cosmochim Acta 52 1585ndash1591

Dallai L Freda C Gaeta M 2004 Oxygen isotope geochemistry of pyroclasticclinopyroxene monitors carbonate contributions to Roman-type ultrapotassicmagmaContrib Mineral Petrol 148 247ndash263

De Natale G Troise C Pingue F Mastrolorenzo G Pappalardo L 2006 The Somma-Vesuvius volcano (Southern Italy) structure dynamics and hazard evaluationEarthSci Rev 74 73ndash111

Deegan FM Troll VR Freda C Misiti V Chadwick JP Mc Leod CL Davidson JP2010 Magmandashcarbonate interaction processes and associated CO2 release atMerapi volcano Indonesia insights from experimental petrologyJ Petrol 511027ndash1051

Dioh E Beziat D Gregoire M Debat P 2009 Origin of rare earth element variationsin clinopyroxene from plutonic and associated volcanic rocks from the FouldeBasin northern Kedougou Inlier Senegal West AfricaEur J Min 21 (5)1029ndash1043

Di Renzo V Di Vito MA Arienzo I Carandente A Civetta L DrsquoAntonio MGiordano F Orsi G Tonarini S 2007 Magmatic History of Somma-Vesuvius onthe Basis of New Geochemical and Isotopic Data from a Deep Borehole (CamaldolidellaTorre) J Petrol 48 753ndash784

Dixon JE Stolper EM 1995 An experimental study of water and carbon dioxidesolubilities in mid-ocean ridge basaltic liquids Part II applications to degassingJPetrol 36 (6) 1633ndash1646

Eiler JM Farley KA Valley JW Hauri E Craig H Hart SR Stolper EM 1997Oxygen isotope variations in ocean Island basalt phenocrystsGeochim CosmochimActa 61 2281ndash2293

Farver JR 2010 Oxygen and hydrogen diffusion in mineralsIn Zhang Y Cherniak DJ(Eds) Diffusion inMinerals andMelts Reviews inMineralogyandGeochemistry 72Mineral Soc Am Chelsea pp 447ndash507

Freda C Gaeta M Misiti V Mollo S Dolfi D Scarlato P 2008 Magmandashcarbonateinteraction an experimental study on ultrapotassic rocks from Alban Hills (CentralItaly)Lithos 101 397ndash415

Freda C Gaeta M Giaccio B Marra F Palladino DM Scarlato P Sottili G 2010CO2-driven large mafic eruptions the Pozzolane Rosse case study from the ColliAlbani Volcanic District (Italy)Bull Volcanol doi101007s00445-010-0406-3

Frezzotti ML De Astis G Dallai L Ghezzo C 2007 Coexisting calc-alkaline andultrapotassic magmatism at Monti Ernici Mid Latina Valley (Latium central Italy)Eur J Miner 19 (4) 479ndash497

FrezzottiML Peccerillo A PanzaG2009 CarbonatemetasomatismandCO2 lithospherendashasthenosphere degassing beneath the Western Mediterranean an integrated modelarising from petrological and geophysical dataChem Geol 262 108ndash120

Fulignati P Kamenetsky VS Marianelli R Sbrana A Mernagh TP 2001 Meltinclusion record of immiscibility between silicate hydrosaline and carbonatemelts applications to skarn genesis at Mount VesuviusGeology 29 1043ndash1046

Gaeta M Freda C Christensen JN Dallai L Marra F Karner DB Scarlato P 2006Time-dependent geochemistry of clinopyroxene from the Alban Hills (Central Italy)clues to the source and evolution of ultrapotassic magmasLithos 86 330ndash346

Gaeta M Di Rocco T Freda C 2009 Carbonate assimilation in open magmaticsystems the role of melt-bearing skarns and cumulate forming processesJ Petrol50 361ndash385

Gasperini D Blichert Toft J Bosch D Del Moro A Macera P Albareacutede F 2002Upwelling of deep mantle material through a plate window evidence from thegeochemistry of Italian basaltic volcanicsJ Geophys Res 107 (B12) 2367

Gilg HA Lima A Somma R Belkin HE De Vivo B Ayuso RA 2001 Isotopegeochemistry and fluid inclusion study of skarns from VesuviusMineral Petrol 73145ndash176

Goff F Love SP Warren RG Counce D Obenholzer J Siebe C Schmidt SC 2001Passive infrared remotesensing evidence for large intermittent CO2 emissions atPopocatepetl volcano MexicoChem Geol 177 133ndash156

Haynes WM 2010 CRC Handbook of Chemistry and Physics (Internet Version 2010)91st Edition CRC PressTaylor and Francis Boca Raton FL

Iacono Marziano G Gaillard F Pichavant M 2007 Limestone assimilation and theorigin of CO2 emissions at the Alban Hills (Central Italy) constraints fromexperimental petrologyJ Volcanol Geotherm Res 166 91ndash105

Iacono Marziano G Gaillard F Pichavant M 2008 Limestone assimilation by basalticmagmas an experimental re-assessment and application to Italian volcanoesCon-trib Mineral Petrol 155 719ndash738

Iacono-Marziano G Gaillard F Scaillet B Pichavant M Chiodini G 2009 Role ofnon-mantle CO2 in the dynamics of volcano degassing the Mount VesuviusexampleGeology 37 319ndash322

Ingrin J Pacaud L Jaoul O 2001 Anisotropy of oxygen diffusion in diopsideEarthPlanet Sci Lett 192 347ndash361

Lvov BV 2002 Mechanism and kinetics of thermal decomposition of carbona-tesThermochim Acta 386 1ndash16

Please cite this article as Dallai L et al Carbonate-derived CO2 purgVesuvius Italy Earth Planet Sci Lett (2011) doi101016jepsl20110

Landi P Bertagnini A Rosi M 1999 Chemical zoning and crystallizationmechanismsin the magma chamber of the Pomici di Base plinian eruption of Somma-Vesuvius(Italy)Contrib Mineral Petrol 135 179ndash197

Loucks R 1996 A precise olivine-augite MgndashFe-exchange geothermometerContribMineral Petrol 125 140ndash150

Marianelli P Meacutetrich N Santacroce R Sbrana A 1995 Mafic magma batches atVesuvius a glass inclusion approach to the modalities of feeding stratovolcanoes-Contrib Mineral Petrol 120 159ndash169

Marianelli P Meacutetrich N Sbrana A 1999 Shallow and deep reservoirs involved inmagma supply of the 1944 eruption of VesuviusBull Volcanol 61 48ndash63

Marianelli P Sbrana A Meacutetrich N Cecchetti A 2005 The deep feeding system ofVesuvius involved in recent violent Strombolian eruptionsGeophys Res Lett 32L02306 doi1010292004GRL021667

Mattey D Lowry D Macpherson C 1994 Oxygen isotope composition of mantleperidotiteEarth Planet Sci Lett 128 (3ndash4) 231ndash241

Matthews A Stolper EM Eiler JM Epstein S 1998 Oxygen isotope fractionationamongmelts minerals and rocks1998 Goldschmidt Conference Toulouse MineralSoc Lon pp 971ndash972

Mollo S Gaeta M Freda C Di Rocco T Misiti V Scarlato P 2010 Carbonateassimilation in magmas a reappraisal based on experimental petrologyLithos 114503ndash514

Morgan DJ Blake S Rogers NW De Vivo B Rolandi G Macdonald RHawkesworth CJ 2004 Time scales of crystal residence and magma chambervolume from modelling of diffusion profiles in phenocrysts Vesuvius 1944EarthPlanet Sci Lett 222 933ndash946

Morgan DJ Blake S Rogers NW De Vivo B Rolandi G Davidson JP 2006 Magmachamber recharge at Vesuvius in the century prior to the eruption of AD79Geology 34 845ndash848

Muehlenbachs K Kushiro I 1974 Oxygen isotope exchange and equilibrium ofsilicates with CO2 or O2Geophysical Laboratory Igneous petrology Experimentaland Field Studies Volatiles in Ultrabasic and Derivative Rock Systems 73 CarnegieInstitute of Washington Yearbook Washington pp 232ndash236

Nabeleck PI 2007 Fluid evolution and kinetics of metamorphic reactions in calc-silicate contact aureoles mdash from H2O to CO2 and backGeology 35 927ndash930

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Patacca E Scandone P 2007 Geological interpretation of the CROP-04 seismic line(Southern Apennines Italy)BollSocGeolIt (ItalJGeosci) Spec (7) 297ndash315

Peccerillo A 1999 Multiple mantle metasomatism in central-southern Italygeochemical effects timing and geodynamic implicationsGeology 27 315ndash318

Peccerillo A Lustrino M 2005 Compositional variation of Plio-Quaternary magma-tism in the circum-Tyrrhenian area Deep versus shallow mantle processes InFoulger GR Natland JH Presnall DC Anderson DL (Eds) Plates plumes andparadigms Geol Soc Am Special Paper 338 421ndash434

Peccerillo A Dallai L Frezzotti ML Kempton PD 2004 Decoupling of geochemicaland SrndashNdndashO-isotopic signatures in the evolution of the Alicudi Volcano (Aeolianarc Italy) implications for the style of magma-crust interaction and for mantlesource compositionLithos 78 (1ndash2) 217ndash233

Peccerillo A Federico M Barbieri M Brilli M Wu TW 2010 Interaction betweenultrapotassic magmas and carbonate rocks evidence from geochemical andisotopic (Sr Nd O) compositions of granular lithic clasts from the Alban HillsVolcano Central ItalyGeochim Cosmochim Acta 74 2999ndash3022

Piochi M Ayuso RA De Vivo B Somma R 2006 Crustal contamination and crystalentrapment during evolution at Mt Somma-Vesuvius volcano Italy geochemicaland Sr isotopic evidenceLithos 86 303ndash329

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Santacroce R Cioni R Marianelli P Sbrana A Sulpizio R Zanchetta GDonahue DJ Joron JL 2008 Age and whole rock-glass compositions ofproximal pyroclastics from themajor explosive eruptions of Somma-Vesuvius areview as a tool for distal tephrostratigraphyJ Volcanol Geotherm Res 1771ndash18

Savelli C 1967 The problem of rock assimilation by Somma-Vesuvius Magma IComposition of Somma and Vesuvius lavasContrib Mineral Petrol 16 328ndash353

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Scandone R Giacomelli L Fattori Speranza F 2008 Persistent activity and violentstrombolian eruptions at Vesuvius between 1631 and 1944J Volcanol GeothermRes 170 167ndash180

Sharp ZD 1995 Oxygen isotope geochemistry of the Al2SiO5 polymorphsAm J Sci295 1058ndash1076

Sigurdsson H Cornell W Carey S 1990 Influence of magma withdrawal oncompositional gradients during the AD 79 Vesuvius eruptionNature 345 519ndash521

Spera FJ Bohrson WA 2001 Energy-constrained open-system magmatic processesI general model and energy-constrained assimilation and fractional crystallization(EC-AFC) formulationJ Petrol 42 999ndash1018

Stanmore BR Gillot P 2005 Review mdash calcination and carbonation of limestoneduring thermal cycling for CO2 sequestrationFuel Process Technol 86 1707ndash1743

Stolper E Epstein S 1991 An experimental study of oxygen isotope partitioningbetween silica glass and CO2 vaporIn Taylor Jr HP et al (Ed) Stable IsotopeGeochemistry A Tribute to Samuel Epstein The Geochemical Society SpecialPublication 3 pp 35ndash51

ing magma at depth Influence on the eruptive activity of Somma-7013

13L Dallai et al Earth and Planetary Science Letters 310 (2011) xxxndashxxx

Sulpizio R Mele D Dellino P La Volpe L 2005 A complex Subplinian-type eruptionfrom low viscosity phonolitic to tephri-phonolitic magma the Pollena eruption ofSomma-Vesuvius (Italy)Bull Volcanol 67 743ndash767

Sulpizio R Cioni R Di Vito MA Mele D Bonasia R Dellino P La Volpe L 2010 TheAvellino eruption of Somma-Vesuvius (38 ka BP) part I stratigraphy chemistryand eruptive mechanismsBull Volcanol 72 539ndash558

Tiepolo M Bottazzi P Palenzona M Vannucci R 2003 A laser probe coupled withICP-double-focusing sector-field mass spectrometer for in situ analysis ofgeological samples and UndashPb dating of zirconCan Mineral 41 259ndash272

Please cite this article as Dallai L et al Carbonate-derived CO2 purgiVesuvius Italy Earth Planet Sci Lett (2011) doi101016jepsl20110

Wenzel T Baumgartner LP Brugmann GE Konnikov EG Kislov EV 2002 Partialmelting and assimilation of dolomitic xenoliths bymafic magma the Ioko-Dovyrenintrusion (North Baikal Region Russia)J Petrol 43 2049ndash2074

Wyllie PJ Boettcher AL 1969 Liquidus phase relations in the system CaOndashO2ndashH2O to40 kilobars pressure with petrological applicationsAm J Sci 267-A 4E9-50E

Ying JF Zhang HF Kita N Morishita Y Shimoda G 2006 Nature and evolution ofLate Cretaceous lithospheric mantle beneath the eastern North China CratonConstraints from petrology and geochemistry of peridotitic xenoliths from JuumlnanShandong Province ChinaEarth Planet Sci Lett 244 622ndash638

ng magma at depth Influence on the eruptive activity of Somma-7013