Active hydrothermal fluids circulation triggering small-scale collapse events: the case of the 2001–2002 fissure in the Lakki Plain (Nisyros Island, Aegean Sea, Greece)

Stefania Venturi*, Franco Tassi, Orlando Vaselli, Georges E. Vougioukalakis, Heba Rashed, Christos Kanellopoulos, Chiara Caponi, Francesco Capecchiacci, Jacopo Cabassi, Andrea Ricci, Luciano Giannini

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)

Abstract

In 2001–2002, two ground collapses occurred in the island of Nisyros (Aegean Sea, Greece), which formed a 600 m long and up to 5 m wide fissure in the vegetated central part of the Lakki Plain caldera. The fissure was alternatively ascribed to tensional stress release and hydrothermal alteration. In this study, we present original data of diffuse CO2 soil fluxes, soil temperatures, mineralogical and chemical composition of the caldera-filling deposits exposed on the fissure walls, and chemical and isotopic composition of interstitial soil gases collected from: the bottom of the fissure, the adjacent vegetated areas, the hydrothermal craters, and selected sites outside the caldera. The occurrence of intense hydrothermal alteration was shown by both mineralogical and chemical analyses of the fissure walls material. Typical mineral assemblage and enrichments in incompatible elements related to advanced argillic alteration, characterizing steam-heated hydrothermal environments, were recognized. Although the low-permeable sediment cover in the Lakki Plain concealed the underneath hydrothermal gas flow, preventing anomalous soil temperatures and CO2 fluxes, the chemical and isotopic composition of the interstitial soil gases revealed an active hydrothermal fluids circulation below the collapsed area, likely controlled by buried structural lineaments. Hydrothermal alteration can then be invoked as the most likely trigger mechanism for the 2001–2002 collapse event.

Original languageEnglish
Pages (from-to)601-626
Number of pages26
JournalNatural Hazards
Volume93
Issue number2
DOIs
Publication statusPublished - 1 Sept 2018

Bibliographical note

Funding Information:
This work was financially supported by a project between IGME-Athens and the Department of Earth Sciences of Florence, the laboratories of Fluid and Rock Geochemistry and Stable Isotope Geochemistry (Department of Earth Sciences of Florence) and the Institute of Geosciences and Earth Resources of the National Research Council of Italy (IGG-CNR Florence). Part of this work was presented as an oral contribution at the EGU General Assembly 2016 (Venturi et al. 2016). E. Calvi (CNR-IGG Pisa), E. Pecchioni (Department of Earth Sciences of Florence) and S. Ciattini (CRIST Florence) are warmly thanked for their help for the IRMS, XRD and XRF analysis, respectively. Many thanks are due to A. Gallorini and A. Raspanti for their help during the sampling campaign. The authors wish to thank two anonymous reviewers for their helpful comments that contributed to improve the first version of the manuscript.

Publisher Copyright:
© 2018, Springer Science+Business Media B.V., part of Springer Nature.

Other keywords

  • Fissuring
  • Ground collapse
  • Hydrothermal alteration
  • Hydrothermal fluid circulation
  • Nisyros Island
  • Volcanic-hydrothermal systems

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