Estudio de los mecanismos que controlan la transición explosiva a efusiva de las erupciones de domo del complejo Teide-Pico Viejo.

Abstract

The Teide-Pico Viejo (PT-PV) stratovolcanoes constitute one of the major potentially active volcanic complexes in Europe. Traditionally, they have been considered to be non-explosive but recent studies have revealed that explosive activity of phonolitic magmas, including plinian and subplinian eruptions and generation of pyroclastic density currents, have also been significant. This explosive activity is mostly related to satellite dome vents, like the one studied in this work, Pico Cabras. Dome-forming eruptions usually present sudden transitions between explosive and effusive activity. A better knowledge of this type of eruptions and the main factors that controls these changes in eruptive styles are required to undertake a comprehensive volcanic hazard assessment of Tenerife Island. In this study, we conduct a petrological and mineral characterization of the different eruption phases of Pico Cabras with the aim of identifying the factors that control these changes in the volcanic activity. Using geothermobarometers, geohygrometers and comparing the results with experimental petrology data we present a model of a compositionally stratified magma chamber at 1 kbar±0.5kbar in which the differences in the eruptive styles are controled by the temperature and the amount of volatiles dissolved in the melt. The explosive phase is related to the upper part of the magma chamber at 725ºC±25ºC and 3,5-5 wt% H2O and the effusive phase with the main body of the chamber at 880ºC±30ºC and 2,5-3 wt% H2O. Also, we report for the first time the present of sodalite, a Cl-rich mineral, in recent PT-PV magmas. This mineral is an indicator of a significant amount of halogen gases within the fluid phase. The release of this kind of volatiles into the atmosphere (specially Cl and Br) have a direct impact on the ozone layer depletion.