Magma reservoirs are thought to grow relatively slowly, assembling incrementally under volatile-saturated conditions. Eruptions may be triggered by injections of volatile-rich melt, or generation of over-pressure due to protracted crystallization. Here, we analyse fluorine, chlorine and water in apatite crystals trapped at different stages of magma evolution, and in melt inclusions from clinopyroxene and biotite crystals expelled during an explosive eruption of the Campi Flegrei caldera, Italy, about 4,000 years ago. We combine our geochemical analyses with thermodynamic modelling to reconstruct the evolution of magmatic volatile contents leading up to the explosive eruption. We find that the magma reservoir remained persistently water-undersaturated throughout most of its lifetime. Even crystals in contact with the melt shortly before eruption show that the magma was volatile-undersaturated. Our models suggest that the melt reached volatile saturation at low temperatures, just before eruption. We suggest that late-stage volatile saturation probably triggered the eruption, and conclude that ‘priming’ of the magma system for eruption may occur on timescales much shorter than the decadal to centennial timescales thought typical for magma reservoir assembly. Thus, surface deformation pulses that record magma assembly at depth beneath Campi Flegrei and other similar magmatic systems may not be immediately followed by an eruption; and explosive eruptions may begin with little warning.
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Roggensack, K., Hervig, R. L., McKnight, S. B. & Williams, S. N. Explosive basaltic volcanism from Cerro Negro Volcano: influence of volatiles on eruptive style. Science 277, 1639–1642 (1997).
Wilson, L. Relationships between pressure, volatile content and ejecta velocity in three types of volcanic explosion. J. Volcanol. Geotherm. Res. 8, 297–313 (1980).
Huppert, H. E. & Woods, A. W. The role of volatiles in magma chamber dynamics. Nature 420, 493–495 (2002).
Woods, A. W. & Koyaguchi, T. Transitions between explosive and effusive eruptions of silicic magmas. Nature 370, 641–644 (1994).
Tait, S., Jaupart, C. & Vergniolle, S. Pressure, gas content and eruption periodicity of a shallow, crystallising magma chamber. Earth Planet. Sci. Lett. 92, 107–123 (1989).
Blake, S. Volatile oversaturation during the evolution of silicic magma chambers as an eruption trigger. J. Geophys. Res. 89, 8237–8244 (1984).
Folch, A. & Martí, J. The generation of overpressure in felsic magma chambers by replenishment. Earth Planet. Sci. Lett. 163, 301–314 (1998).
Sparks, S. R. J., Sigurdsson, H. & Wilson, L. Magma mixing: a mechanism for triggering acid explosive eruptions. Nature 267, 315–318 (1977).
Arienzo, I., Moretti, R., Civetta, L., Orsi, G. & Papale, P. 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 (2010).
Isaia, R., D’Antonio, M., Dell’Erba, F., Di Vito, M. & Orsi, G. The Astroni volcano: the only example of closely spaced eruptions in the same vent area during the recent history of the Campi Flegrei caldera (Italy). J. Volcanol. Geotherm. Res. 133, 171–192 (2004).
Humphreys, M. C. S., Blundy, J. D. & Sparks, R. S. J. Shallow-level decompression crystallisation and deep magma supply at Shiveluch Volcano. Contrib. Mineral. Petrol. 155, 45–61 (2008).
Piccoli, P. & Candela, P. Apatite in felsic rocks; a model for the estimation of initial halogen concentrations in the Bishop Tuff (Long Valley) and Tuolumne Intrusive Suite (Sierra Nevada Batholith) magmas. Am. J. Sci. 294, 92–135 (1994).
Boyce, J. W. & Hervig, R. L. Magmatic degassing histories from apatite volatile stratigraphy. Geology 36, 63–66 (2008).
Scott, J. A., Humphreys, M. C. S., Mather, T. A., Pyle, D. M. & Stock, M. J. Insights into the behaviour of S, F, and Cl at Santiaguito Volcano, Guatemala, from apatite and glass. Lithos 232, 375–394 (2015).
McCubbin, F. M. et al. Fluorine and chlorine abundances in lunar apatite: implications for heterogeneous distributions of magmatic volatiles in the lunar interior. Geochim. Cosmochim. Acta 75, 5073–5093 (2011).
Boyce, J. W., Tomlinson, S. M., McCubbin, F. M., Greenwood, J. P. & Treiman, A. H. The lunar apatite paradox. Science 344, 400–402 (2014).
Lowenstern, J. B. in Magmas, Fluids, and Ore Deposits (ed. Thompson, J. F. H.) 71–89 (Mineralogical Society of Canada, 1995).
Smith, V. C., Isaia, R. & Pearce, N. J. G. Tephrostratigraphy and glass compositions of post-15 kyr Campi Flegrei eruptions: implications for eruption history and chronostratigraphic markers. Quat. Sci. Rev. 30, 3638–3660 (2011).
Peng, G., Luhr, J. F. & McGee, J. J. Factors controlling sulfur concentrations in volcanic apatite. Am. Mineral. 82, 1210–1224 (1997).
Nadeau, S. L., Epstein, S. & Stolper, E. Hydrogen and carbon abundances and isotopic ratios in apatite from alkaline intrusive complexes, with a focus on carbonatites. Geochim. Cosmochim. Acta 63, 1837–1851 (1999).
Webster, J. D., Goldoff, B., Sintoni, M. F., Shimizu, N. & De Vivo, B. C–O–H–Cl–S–F volatile solubilities, partitioning, and mixing in phonolitic–trachytic melts and aqueous-carbonic vapor ± saline liquid at 200 MPa. J. Petrol. 55, 2217–2248 (2014).
Marianelli, P., Sbrana, A. & Proto, M. Magma chamber of the Campi Flegrei supervolcano at the time of eruption of the Campanian Ignimbrite. Geology 34, 937–940 (2006).
Gualda, G. A. R., Ghiorso, M. S., Lemons, R. V. & Carley, T. L. Rhyolite-MELTS: a modified calibration of MELTS optimized for silica-rich, fluid-bearing magmatic systems. J. Petrol. 53, 875–890 (2012).
Fowler, S. J., Spera, F. J., Bohrson, W. A., Belkin, H. E. & De Vivo, B. Phase equilibria constraints on the chemical and physical evolution of the Campanian Ignimbrite. J. Petrol. 48, 459–493 (2007).
Cannatelli, C. Understanding magma evolution at Campi Flegrei (Campania, Italy) volcanic complex using melt inclusions and phase equilibria. Mineral. Petrol. 104, 29–42 (2012).
Bohrson, W. A. et al. Petrogenesis of the Campanian Ignimbrite: Implications for Crystal-Melt Separation and Open-System Processes from Major and Trace Elements and Th Isotopic Data (Developments in Volcanology, Elsevier, 2006).
Civetta, L., Carluccio, E., Innocenti, F., Sbrana, A. & Taddeucci, G. Magma chamber evolution under the Phlegraean Fields during the last 10 ka: trace element and isotope data. Eur. J. Mineral. 3, 415–428 (1991).
Cannatelli, C. et al. Geochemistry of melt inclusions from the Fondo Riccio and Minopoli 1 eruptions at Campi Flegrei (Italy). Chem. Geol. 237, 418–432 (2007).
Zollo, A. et al. Seismic reflections reveal a massive melt layer feeding Campi Flegrei caldera. Geophys. Res. Lett. 35, L12306 (2008).
De Siena, L., Del Pezzo, E. & Bianco, F. Seismic attenuation imaging of Campi Flegrei: evidence of gas reservoirs, hydrothermal basins, and feeding systems. J. Geophys. Res. 115, B09312 (2010).
Woo, J. Y. L. & Kilburn, C. R. J. Intrusion and deformation at Campi Flegrei, southern Italy: sills, dikes, and regional extension. J. Geophys. Res. 115, B12210 (2010).
Carroll, M. R. & Blank, J. G. The solubility of H2O in phonolitic melts. Am. Mineral. 82, 549–556 (1997).
Candela, P. A. Toward a thermodynamic model for the halogens in magmatic systems: an application to melt–vapor–apatite equilibria. Chem. Geol. 57, 289–301 (1986).
Signorelli, S. & Carroll, M. R. Solubility and fluid–melt partitioning of Cl in hydrous phonolitic melts. Geochim. Cosmochim. Acta 64, 2851–2862 (2000).
Webster, J. D. & De Vivo, B. Experimental and modeled solubilities of chlorine in aluminosilicate melts, consequences of magma evolution, and implications for exsolution of hydrous chloride melt at Mt. Somma-Vesuvius. Am. Mineral. 87, 1046–1061 (2002).
Woods, S. C., Mackwell, S. & Dyar, D. Hydrogen in diopside: diffusion profiles. Am. Mineral. 85, 480–487 (2000).
Danyushevsky, L. V., McNeill, A. W. & Sobolev, A. V. Experimental and petrological studies of melt inclusions in phenocrysts from mantle-derived magmas: an overview of techniques, advantages and complications. Chem. Geol. 183, 5–24 (2002).
Baker, D. R., Freda, C., Brooker, R. A. & Scarlato, P. Volatile diffusion in silicate melts and its effects on melt inclusions. Ann. Geophys. 48, 699–717 (2005).
Brenan, J. Kinetics of fluorine, chlorine and hydroxyl exchange in fluorapatite. Chem. Geol. 110, 195–210 (1993).
Bodnar, R. J. et al. Quantitative model for magma degassing and ground deformation (bradyseism) at Campi Flegrei, Italy: implications for future eruptions. Geology 35, 791–794 (2007).
Tonarini, S., D’Antonio, M., Di Vito, M. A., Orsi, G. & Carandente, A. Geochemical and B–Sr–Nd isotopic evidence for mingling and mixing processes in the magmatic system that fed the Astroni volcano (4.1–3.8 ka) within the Campi Flegrei caldera (southern Italy). Lithos 107, 135–151 (2009).
Schmidt, B. C. & Behrens, H. Water solubility in phonolite melts: Influence of melt composition and temperature. Chem. Geol. 256, 259–268 (2008).
Blake, S. Volcanism and the dynamics of open magma chambers. Nature 289, 783–785 (1981).
Guidoboni, E. & Ciuccarelli, C. The Campi Flegrei caldera: historical revision and new data on seismic crises, bradyseisms, the Monte Nuovo eruption and ensuing earthquakes (twelfth century 1582 AD). Bull. Volcanol. 73, 655–677 (2011).
Chiodini, G. et al. Evidence of thermal-driven processes triggering the 2005–2014 unrest at Campi Flegrei caldera. Earth Planet. Sci. Lett. 414, 58–67 (2015).
Annen, C., Blundy, J. D. & Sparks, R. S. J. The genesis of intermediate and silicic magmas in deep crustal hot zones. J. Petrol. 47, 505–539 (2006).
Chaussard, E. & Amelung, F. Regional controls on magma ascent and storage in volcanic arcs. Geochem. Geophys. Geosyst. 15, 1407–1418 (2014).
Druitt, T. H., Costa, F., Deloule, E., Dungan, M. & Scaillet, B. Decadal to monthly timescales of magma transfer and reservoir growth at a caldera volcano. Nature 482, 77–80 (2012).
Biggs, J. et al. Global link between deformation and volcanic eruption quantified by satellite imagery. Nature Commun. 5, 3471 (2014).
Parks, M. M. et al. Evolution of Santorini Volcano dominated by episodic and rapid fluxes of melt from depth. Nature Geosci. 5, 749–754 (2012).
Stormer, J. C. Jr, Pierson, M. L. & Tacker, R. C. Variation of F and Cl X-ray intensity due to anisotropic diffusion in apatite. Am. Mineral. 78, 641–648 (1993).
Stock, M. J., Humphreys, M. C. S., Smith, V. C., Johnson, R. D. & Pyle, D. M. New constraints on electron-beam induced halogen migration in apatite. Am. Mineral. 100, 281–293 (2015).
Goldoff, B., Webster, J. D. & Harlov, D. E. Characterization of fluor-chlorapatites by electron probe microanalysis with a focus on time-dependent intensity variation of halogens. Am. Mineral. 97, 1103–1115 (2012).
Humphreys, M. C. S., Kearns, S. L. & Blundy, J. D. SIMS investigation of electron-beam damage to hydrous, rhyolitic glasses: implications for melt inclusion analysis. Am. Mineral. 91, 667–679 (2006).
This research was funded by a NERC studentship NE/K500811/01 awarded to M.J.S. and a NERC Edinburgh Ion Microprobe Facility grant (IMF519/0514). M.C.S.H. was supported by a Royal Society University Research Fellowship. M.C.S.H. and V.C.S. acknowledge funding from NERC grant NE/K003852/1. This work has benefited from discussions with R. Brooker, J. Riker and P. Candela. The review of W. Bohrson significantly improved the manuscript. We are grateful to R. Hinton and N. Charnley for assistance with SIMS and SEM analysis, respectively. We also thank D. Harlov for providing synthetic apatite standards for SIMS calibration and R. van Elsas for technical support during mineral separation.
The authors declare no competing financial interests.
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Stock, M., Humphreys, M., Smith, V. et al. Late-stage volatile saturation as a potential trigger for explosive volcanic eruptions. Nature Geosci 9, 249–254 (2016) doi:10.1038/ngeo2639
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