Poly-phase alteration history of the kaolinitized 'Cava di Caolino' volcanics (Lipari Island, southern Italy)

S. Decrée, A. Bernard, J. Yans, Th De Putter

    Research output: Contribution to journalArticlepeer-review

    Abstract

    A 65 m thick altered volcanic profile was studied in the Cava di Caolino (Lipari Island) in order to (1) identify the alteration event(s), (2) model these events, and (3) propose estimates of the degree of chemical alteration (CIA, chemical index of alteration). Two mineral parageneses were identified: one comprising silico-aluminous phases, with well crystallized kaolinite (type 1), and the other comprising sulphates, with kaolinite as fracture infilling (type 2). The geochemistry of fluids analysed from a local hot spring (40°C, pH ε7 8) allowed modelling of the observed silico-aluminous paragenesis. A later fumarolic event is suggested to be responsible for the sulphate paragenesis. The main stage of hydrothermal alteration lasted for ∼50 ky, was marked by an increase in the CIA from the protolith (∼52) to the alterites (∼98), and resulted in the alteration of a 65 m thick series. Such data could be used to predict the alteration of volcanic rocks around underground nuclear waste repositories.

    Original languageEnglish
    Pages (from-to)153-165
    Number of pages13
    JournalClay Minerals
    Volume40
    Issue number2
    DOIs
    Publication statusPublished - 1 Jun 2005

    Keywords

    • Acid fluids
    • Alteration
    • Hydrothermal alkaline fluids
    • Italy
    • Kaolinite
    • Lipari Island
    • Radioactive waste repositories sulphates

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