Multiple magma degassing sources at an explosive volcano

Persistent degassing of closed-conduit explosive volcanoes may be used to inspect and monitor
magmatic processes. After interaction with shallow hydrothermal fluids, volcanic gases collected at
surface can differ substantially from those exsolved from magma. We report here on an innovative
approach to identify and separate the contribution of variable magmatic components from fumarolic
gases, by processing the 30-year-long geochemical dataset from the Campi Flegrei caldera, Southern
Italy. The geochemical record shows periodic variations, which are well correlated with geophysical
signals. Such variations are interpreted as due to the time-varying interplay of two magma degassing
sources, each differing in size, depth, composition, and cooling/crystallization histories. Similar
multiple degassing sources are common at explosive volcanoes, with frequent ascent and intrusion
of small magma batches. Our innovative method permits the identification of those magma batches,
which contributes to the interpretation of unrest signals, forecasting and assessment of volcanic
hazards

Aiuppa, A., Moretti, R., Federico, C., Giudice, G., Gurrieri, S., Liuzzo, M., Papale, P.,
Shinohara, H., Valenza, M., 2007. Forecasting Etna eruptions by real-time
observation of volcanic gas composition. Geology 35 (12), 1115–1118.
Aiuppa, A., Bertagnini, A., Me´trich, N., Moretti, R., Di Muro, A., Liuzzo, M.,
Tamburello, G., 2010. A degassing model for Stromboli volcano. Earth Planet.
Sci. Lett. 295, 195–204.
Allard, P., Maiorani, A., Tedesco, D., Cortecci, G., Turi, B., 1991. Isotopic study of the
origin of sulfur and carbon in Solfatara fumaroles, Campi Flegrei caldera. J.
Volcanol. Geotherm. Res. 48, 139–159.
Arienzo, I., Moretti, R., Civetta, L., Orsi, G., Papale, P., 2010. The feeding system of
Agnano-Monte Spina eruption Campi Flegrei (Italy): dragging the past into
present activity and future scenarios. Chem. Geol. 270, 135–147.
Bachmann, O., Bergantz, G.W., 2006. Gas percolation in upper crustal silicic crystal
mushes as a mechanism for upward heat advection and rejuvenation of nearsolidus magma bodies. J. Volcanol. Geotherm. Res. 149, 85–102.
Baker, D.R., Moretti, R., 2011. Modeling the solubility of sulfur in magmas: a 50-
year old geochemical challenge. Rev. Min. Geochem. 58, 167–213.
Belonoshko, A.B., Shi, P., Saxena, S.K., 1992. SUPERFLUID: a FORTRAN 77 program
for calculation of Gibbs free energy and volume of C–H–O–N–S–Ar mixtures.
Comp. Geosci. 18, 1267–1269.
Berrino, G., 1994. Gravity changes induced by height–mass variations at the Campi
Flegrei caldera. J. Volcanol. Geotherm. Res. 61, 293–309.
Caliro, S., Chiodini, G., Moretti, R., Avino, R., Granieri, D., Russo, M., Fiebig, J., 2007.
The origin of the fumaroles of La Solfatara (Campi Flegrei, South Italy).
Geochim. Cosmochim. Acta 71, 3040–3055.
Chiodini, G., Cioni, R., Magro, G., Marini, L., Panichi, C., Raco, B., Russo, M., 1996.
Geochemical and isotopic variations of Bocca Grande fumaroles (Solfatara
volcano, Phlegrean Fields). Acta Vulcanol. 8, 228–232.
Chiodini, G., Allard, P., Caliro, S., Parello, F., 2000. 18O exchange between steam and
carbon dioxide in volcanic and hydrothermal gases; implications for the
source of water. Geochim. Cosmochim. Acta 64, 2479–2488.
Chiodini, G., Caliro, S., Caramanna, G., Granieri, D., Minopoli, C., Moretti, R.,
Perrotta, L., 2006. Geochemistry of the submarine gaseous emissions of
Panarea (Aeolian Islands, Southern Italy): magmatic vs. hydrothermal origin
and implications for volcanic surveillance. Pure Appl. Geophys. 163, 759–780.
Chiodini, G., Caliro, S., Cardellini, C., Granieri, D., Avino, R., Baldini, A., Donnini, M.,
Minopoli, C., 2010a. Long-term variations of the Campi Flegrei, Italy, volcanic
system as revealed by the monitoring of hydrothermal activity. J. Geophys.
Res. 115, B03205, http://dx.doi.org/10.1029/2008JB006258.
Chiodini, G., Avino, R., Caliro, S., Minopoli, C., 2011. Temperature and pressure gas
geoindicators at the Solfatara fumaroles (Campi Flegrei). Ann. Geophys. 54, 2,
http://dx.doi.org/10.4401/ag-5002.
Chiodini, G., Caliro, S., De Martino, P., Gherardi, F., 2010b. Early signals of new
volcanic unrest at Campi Flegrei caldera? Insights from geochemical data and
physical simulations. Geology, 11, Q04005, http://dx.doi.org/10.1130/G33251.1.
D’Auria, L., Giudicepietro, F., Aquino, I., Borriello, G., Del Gaudio, C., Lo Bascio, D.,
Martini, M., Ricciardi, G.P., Ricciolino, P., Ricco, C., 2011. Repeated fluid transfer
episodes as a mechanism for the recent dynamics of Campi Flegrei caldera (1989–
2010). J. Geophys. Res. 116, B04313, http://dx.doi.org/10.1029/2010JB007837.
D’Auria, L., Giudicepietro, F., Martini, M., Lanari, R., 2012. The 4D imaging of the
source of round deformation at Campi Flegrei caldera (southern Italy). J.
Geophys. Res. 117, B08209, http://dx.doi.org/10.1029/2012JB009181.
De Siena, L., Del Pezzo, E., Bianco, F., 2010. Seismic attenuation imaging of Campi
Flegrei: evidence of gas reservoirs, hydrothermal basins, and feeding systems.
J. Geophys. Res. 115, B09312, http://dx.doi.org/10.1029/2009JB006938.
Di Renzo, V., Arienzo, I., Civetta, L., D’Antonio, M., Tonarini, S., Di Vito, M.A., Orsi, G.,
2011. The magmatic feeding system of the Campi Flegrei caldera: architecture
and temporal evolution. Chem. Geol. 281, 227–241.
Edmonds, M., Aiuppa, A., Humphreys, M., Moretti, R., Giudice, G., Martin, R., Herd, R.A.,
Christopher, T., 2012. Excess volatiles supplied by mingling of mafic magma at an
andesitic arc volcano. Geophys. Geochem. Geosyst. 40, 943–946.
Fabbrizio, A., Scaillet, B., Carroll, M.R., 2009. Estimation of pre-eruptive magmatic
water fugacity in the Phlegrean Fields, Naples, Italy. Eur. J. Mineral. 21, 27–116.
Giggenbach, W.F., 1987. Redox processes governing the chemistry of fumarolic gas
discharges from White Island New Zealand. Appl. Geochem. 2, 143–161.
Giggenbach, W.F., 1996. Chemical composition of volcanic gases. In: Scarpa, R.,
Tilling, R.I. (Eds.), Monitoring and Mitigation of Volcano Hazards. Springer,
New York, pp. 202–226.
Gottsmann, J., Folch, A., Rymer, H., 2006. Unrest and Campi Flegrei: a contribution to
the magmatic versus hydrothermal debate from inverse and finite element
modeling. J. Geophys. Res. 111, B07203, http://dx.doi:org/10.10292005JB003745.
Heidemann, R., Khalil, A., 1980. The calculation of critical points. AIChe J. 26, 769.
Hoefs, J., 2004. Stable Isotope Geochemistry. Springer-Verlag, Berlin Heidelberg.
(201 pp.).
Holloway, J.R., Blank, J.G., 1994. Application of experimental results to C–O–H
species in natural melts. Rev. Mineral. 30, 187–230.
Lasaga, A., 1998. Kinetic Theory in the Earth Sciences. Princeton University Press,
Princeton.
Longo, A., Vassalli, M., Papale, P., Barsanti, M., 2006. Numerical simulation of
convection and mixing in magma chambers replenished with CO2-rich magma.
Geophys. Res. Lett. 33, L21305, http://dx.doi.org/10.1029/2006GL027760.
Mangiacapra, A., Moretti, R., Rutherford, M., Civetta, L., Orsi, G., Papale, P., 2008.
The deep magmatic system of the Campi Flegrei caldera (Italy). Geophys. Res.
Lett. 35, L21304, http://dx.doi.org/10.1029/2008GL035550.
Marini, L., Moretti, R., Accornero, M., 2011. Sulfur isotopes in magmatic-hydrothermal
systems, melts, and magmas. Rev. Mineral. Geochem. 73, 423–492.
Maddox, R., Lilly, L., 1990. Gas Conditioning and Processing, vol. 3, Computer
Applications and Production/Processing Facilities. Campbell Petroleum Series.
Michelsen, M., Heidemann, R., 1981. Calculation of critical points from cubic twoconstant equation of state. AIChE J., 27.
Moretti, R., 2005. Polymerisation, basicity, oxidation state and their role in ionic
modelling of silicate melts. Ann. Geophys. 48, 583–608.
Moretti, R., Papale, P., Ottonello, G., 2003. A model for the saturation of C–H–O–S
fluids in silicate melts. In: Oppenheimer, C., Pyle, D.M., Barclay, J. (Eds.), Volcanic
Degassing, 213. Geological Society London Special Publication, pp. 81–101.
Moretti, R., Papale, P., 2004. On the oxidation state and volatile behavior in
multicomponent gas-melt equilibria. Chem. Geol. 213, 265–280.
Moretti, R., Ottonello, G., 2005. Solubility and speciation of sulfur in silicate melts:
the Conjugated-Toop-Samis-Flood-Grjotheim (CTSFG) model. Geochim. Cosmochim. Acta 69, 801–823.
Moretti, R., Baker, D.R., 2008. Modeling of the interplay of fO2 and fS2 along the
FeS–Silicate Melt equilibrium. Chem. Geol. 256, 286–298.
Moretti, R., Arienzo, I., Civetta, L., Orsi, G., D’Antonio, M.The deep plumbing system
of the Ischia island: a physico-chemical window on the fluid-saturated and
CO2-sustained Neapolitan volcanism (Southern Italy). J. Petrol., http://dx.doi.
org/10.1093/petrology/egt002, in press.
Mormone, A., Piochi, M., Bellatreccia, F., De Astis, G., Moretti, R., Della Ventura, G.,
Cavallo, A., Mangiacapra, A., 2011. A CO2-rich magma source beneath the
Phlegraean Volcanic District (Southern Italy): evidence from a melt inclusion
study. Chem. Geol. 287, 66–80.
Newhall, C.G., Dzurisin, D., 1988. Historical unrest at large calderas of the world.
U.S. Geological Survey Bulletin, 2nd vol.
Oppenheimer, C., Moretti, R., Kyle, P., Eschenbacher, A., Lowenstern, J., Hervig, G,
Dunbar, N., 2011. Mantle to surface gas trigger of the alkalic intraplate Erebus
volcano, Antarctica. Earth Planet. Sci. Lett. 306, 261–271.
Orsi, G., de Vita, S., Di Vito, M.A., 1996. The restless, resurgent Campi Flegrei nested
caldera (Italy): constraints on its evolution and configuration. J. Volcanol.
Geotherm. Res. 74, 179–214.
Orsi, G., Civetta, L., Del Gaudio, C., de Vita, S., Di Vito, M.A., Isaia, R., Petrazzuoli, S.,
Ricciardi, G., Ricco, C., 1999. Short-term ground deformations and seismicity in
the nested Campi Flegrei caldera (Italy): an example of active block resurgence
in a densely populated area. J. Volcanol. Geotherm. Res. 91, 415–451.
Orsi, G., Di Vito, M.A., Isaia, R., 2004. Volcanic hazard assessment at the restless
Campi Flegrei caldera. Bull. Volcanol. 66, 514–530.
Orsi, G., Di Vito, M.A., Selva, J., Marzocchi, W., 2009. Long-term forecast of eruption
style and size at Campi Flegrei caldera (Italy). Earth Planet. Sci. Lett. 287, 265–276.
Parfitt, E.A., Wilson, L., 2008. Fundamentals of Physical Volcanology. Blackwell
Publishing, Oxford.
Papale, P., Moretti, R., Barbato, D., 2006. The compositional dependence of the
saturation surface of H2OþCO2 fluids in silicate melts. Chem. Geol. 229,
78–95.
Peluso, F., Arienzo, I., 2007. Experimental determination of permeability of
Neapolitan Yellow Tuff. J. Volcanol. Geotherm. Res. 160, 125–136.
Richet, P., Bottinga, Y., Javoy, M., 1977. A review of H, C, N, O, S and Cl stable
isotope fractionation among gaseous molecules. Annu. Rev. Earth Planet. Sci.
Lett. 5, 65–110.
Roach, A.L., 2005. The Evolution of Silicic Magmatism in the Post-Caldera
Volcanism of the Phlegrean Fields, Italy. Ph.D. Thesis. Brown University.
Selva, J., Orsi, G., Di Vito, M.A., Marzocchi, W., Sandri, L., 2012. Probability hazard
map for future vent opening at the Campi Flegrei caldera, Italy. Bull. Volcanol.
74, 497–510
Shinohara, H., 2008. Excess degassing from volcanoes and its role on eruptive and
intrusive activity. Rev. Geophys. 46, RG4005.
Symonds, R.B., Gerlach, T.M., Reed, M.H., 1991. Magmatic gas scrubbing: implication for volcano monitoring. J. Volcanol. Geotherm. Res. 108, 303–341.
Todesco, M., Berrino, G., 2005. Modeling hydrothermal fluid circulation and gravity
signals at the Phlegraean Fields caldera. Earth Planet. Sci. Lett. 240, 328–338.
Todesco, M., Rinaldi, A.P., Bonafede, M., 2010. Modeling of unrest signals in
heterogeneous hydrothermal systems. J. Geophys, Res. 115, B09213, http://d
x.doi.org/10.1029/2010JB007474.
Trasatti, E., Bonafede, M., Ferrari, C., Giunchi, C., Berrino, G., 2011. On deformation
sources in volcanic areas: modeling the Campi Flegrei (Italy) 1982–84 unrest.
Earth Planet. Sci. Lett. 306, 175–185.
Turi, B., Taylor, J.H.P., Ferrara, G., 1991. Comparison of 18O/16O and 87Sr/86Sr in
volcanic rocks from the Pontine Islands, M. Ernici, and Campania with areas of Italy. In: Taylor, H.P., O’Neil, J.R., Kaplan, I.R. (Eds.), Stable Isotope
Geochemistry: A tribute to Samuel Epstein, vol. 3. Geochemical Society Special
Publication, pp. 307–324.
Woo, J.Y.L., Kilburn, C.R.J., 2010. Intrusion and deformation at Campi Flegrei,
southern Italy: sills, dikes, and regional extension. J. Geophys. Res. 115,
B12210, http://dx.doi.org/10.1029/2009JB006913.
Zhao, Z.-F., Zheng, Y.-F., 2003. Calculation of oxygen isotope fractionation in
magmatic rocks. Chem. Geol. 193, 59–80.
Zheng, Y.F., 1993. Calculation of oxygen isotope fractionation in anhydrous silicate
minerals. Geochim. Cosmochim. Acta 57, 1079–1091.
Zollo, A., Maercklin, N., Vassallo, M., Dello Iacono, D., Virieux, J., Gasparini, P., 2008.
Seismic reflections reveal a massive melt layer under Campi Flegrei volcanic
field. Geophys. Res. Lett. 35, L12306, http://dx.doi.org/10.1029/2008GL034242.