Bulletin of Volcanology

, Volume 68, Issue 2, pp 118–134

Geochemical monitoring of the 2002–2003 eruption at Stromboli volcano (Italy): precursory changes in the carbon and helium isotopic composition of fumarole gases and thermal waters

Authors

  • G. Capasso
    • Istituto Nazionale di Geofisica e Vulcanologia
  • M. L. Carapezza
    • Istituto Nazionale di Geofisica e Vulcanologia
    • Istituto Nazionale di Geofisica e Vulcanologia
  • S. Inguaggiato
    • Istituto Nazionale di Geofisica e Vulcanologia
  • A. Rizzo
    • Istituto Nazionale di Geofisica e Vulcanologia
Research Article

DOI: 10.1007/s00445-005-0427-5

Cite this article as:
Capasso, G., Carapezza, M.L., Federico, C. et al. Bull Volcanol (2005) 68: 118. doi:10.1007/s00445-005-0427-5

Abstract

Significant changes in the helium and carbon isotopic composition of shallow thermal waters vs. gas and a crater fumarolic gas have been recorded at Stromboli prior and during the 2002–2003 eruption. The3He/4He ratios corrected for air contamination (Rc/Ra), and δ13C of fumarolic gases gradually increased from May to November 2002 before the eruption onset. These variations imply early degassing of a gas-rich magma at depth that likely fed both the intense Strombolian activity and small lava overflows recorded during that period. The lava effusion of late December 2002 was shortly preceded by a marked Rc/Ra decrease both in water and fumarolic gases. Comparison of He/CO2 and CH4/CO2 ratios in dissolved gas and with\({\rm \delta }^{13} {\rm C}_{{\rm CO}_2 }\) values rules out the Rc/Ra decrease due to an increasing input of radiogenic4He. The Rc/Ra decrease is attributed to the He isotope fractionation during rapid magma ascent and degassing. A new uprising of 3He-rich magma probably occurred in January to February 2003, when Rc/Ra ratios displayed the highest values in dissolved gases ever measured before (4.56 Rc/Ra). The increase in He/CO2 and CH4/CO2 ratios and decrease in δ13C of dissolved CO2 was recorded after the 5 April 2003 explosive paroxysm, likely caused by enhanced gas-water interaction inducing CO2 dissolution. No anomalous Rc/Ra values were recorded in the same period, when usual Strombolian activity gradually resumed.

Keywords

StromboliEruptionGeochemistryHeliumIsotopesMagma ascentDissolved gases

Copyright information

© Springer-Verlag 2005