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Volcano-tectonic controls on magma evolution at Campi Flegrei, a long-lived caldera system

Fay M. Amstutz 1, Michael J. Stock1, Victoria C. Smith2, Roberto Isaia3, Stefano Vitale4, Elliot J. Carter1,5, Jacopo Natale6, Adrian Boyce7, David van Acken8, J. Stephen Daly8

  • Affiliations: 1Department of Geology, Trinity College Dublin, Dublin 2, Ireland; 2School of Archaeology, University of Oxford, Oxford, UK; 3Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Vesuviano, Naples, Italy; 4Dipartimento di Scienze della Terra, dell\'Ambiente e delle Risorse (DiSTAR), Università di Napoli Federico II, Italy; 5School of Geography, Geology and the Environment, Keele University, Staffordshire, UK; 6Dipartimento di Scienze della Terra e Geoambientali, Università degli Studi di Bari Aldo Moro, 70125 Bari, Italy; 7Scottish Universities Environmental Research Centre, Rankine Avenue, East Kilbride, UK; 8UCD School of Earth Sciences, University College Dublin, Dublin 4, Ireland.

  • Presentation type: Poster

  • Presentation time: Friday 16:30 - 18:00, Room Poster Hall

  • Poster Board Number: 201

  • Programme No: 3.10.7

  • Theme 3 > Session 10

Abstract

Campi Flegrei volcano (Italy) is one of the most hazardous volcanoes on Earth, having produced >70 eruptions in the past 15 kyr and currently showing signs of unrest within a densely populated region. Eruptions in the last 15 kyr span a range of eruptive styles and compositions, broadly correlating with different spatial/structural locations of vents within the larger caldera system. Variability in glass O, Sr, Nd, and Pb isotope composition of erupted products also correlates with vent structural setting: eruptions along caldera rim faults have isotopic compositions which deviate further from typical mantle source values than those from the central or western caldera. Rhyolite-MELTS thermodynamic modelling allowed identification of intensive variables (pressure, water content, oxygen fugacity) which best reproduce the liquid line of descent of glass data from post-15 ka Campi Flegrei eruptions. Our results are consistent with previous studies in failing to fully reproduce the compositional diversity of Campi Flegrei magmas through fractional crystallisation alone, highlighting the important role of country rock assimilation. Isotopic variation between eruptions, outside the range expected for typical mantle-derived magmas evolving through fractional crystallisation, attests to variations in the amount/type of assimilated material. Comparison with potential basement rocks suggests Palaeozoic metamorphic basement is the likely contaminant of eruptions from caldera rim faults whereas syenitic restite likely contaminates central and western caldera eruptions. Our results demonstrate a link between vents' spatial/structural locations and processes operating within the magmatic system, suggesting magmatic evolution at long-lived caldera systems is inherently tied to the volcano-tectonic setting of vents.