Halogen (Cl, F) release during explosive, effusive, and intrusive phases of the 2011 rhyolitic eruption at Cordón Caulle volcano (Chile)

C Ian Schipper,Jonathan M Castro,Ben M Kennedy,Bruce W Christenson,Alessandro Aiuppa,Hugh Tuffen,Brent Alloway,Gilles Seropian,Pablo Forte

doi:10.30909/vol.02.01.7390

Abstract

We investigate sulphur, chlorine and fluorine release during explosive, effusive and intrusive phases of the 2011 Cordón Caulle eruption, with a focus on halogen devolatilization. Petrological analysis shows halogen release to have been promoted by isobaric crystallization in slowly-cooled magma that was emplaced in a lava flow and sub-vent intrusion. Fluorine in particular mobilized only after extensive groundmass crystallization and incipient devitrification. By 2017, the gas emitted from vent-proximal fumaroles had hydrothermal compositions, with HCl/HF ratios decreasing with decreasing temperature. We estimate that the eruption could eventually emit up to 0.84 Mt of SO2, 6.3 Mt of HCl, and 1.9 Mt of HF, but only ~7% and ~2% of total HCl and HF were emitted during explosive phases, and significant halogens are yet to be released from the intrusion. Halogen devolatilization and its associated hazards can persist long after the cessation of rhyolite eruptions with complex magma emplacement mechanisms.

Highlights

We investigate sulphur, chlorine and fluorine release during explosive, effusive and intrusive phases the 20112012 Cordón Caulle eruption, with a focus on the halogens
We examine the release of chlorine and fluorine, and sulphur, during different phases of the 2011–2012 rhyolite eruption at Cordón Caulle volcano (Chile), in order to establish the degree and timing of halogen output during explosive, effusive, and intrusive rhyolite volcanism
The compositions of gases discharged from active fumaroles on the Cordón Caulle edifice were analysed in December 2017

Summary

Introduction

Chlorine and fluorine release during explosive, effusive and intrusive phases the 20112012 Cordón Caulle eruption, with a focus on the halogens. Their release from ascending magma is not a simple consequence of decompression, and conditions of magma emplacement are important in controlling if and how they become mobile [Kilinc and Burnham 1972; Villemant and Boudon 1999; Edmonds et al 2002] They do not drive eruptions [e.g. like H2O and CO2: Cashman 2004], or provide -measured proxies for magmatic vitality [e.g. like sulphur species: Giggenbach 1996; Symonds et al 2001], they can significantly influence melt properties [e.g. The importance of slow isobaric crystallisation to Cl release manifests during eruptions as HCl emissions being weaker during explosive phases and stronger during effusive phases of chemically equivalent magma [Edmonds et al 2002]

Methods

Results

Conclusion