Basement control on volcanic edifice stability

: application to Mount Etna

Abstract

Volcanic edifices are commonly unstable, and Mount Etna presents instability located in its eastern and southern sector. The basement of Mount Etna is characterized by sedimentary formations tectonically deformed during the Africa-Europe collision, structurally dissected by several active fault systems and subjected to magmatic conditions. This PhD thesis is based on laboratory investigations with the aim of answering two main questions. 1) What is the influence that temperature and water have on carbonate terms belonging to the African plate? Carbonate rock samples belonging to the African plateau in subduction under the volcanic edifice were chosen as representative of the carbonate lithologies making up the basement and tested under relevant triaxial conditions. The results demonstrate how sensitive the rock is to the thermal treatment applied to mimic temperature gradient induced by dyke intrusion and to the presence of water (e.g. deep hydrothermal conditions). 2) What is then the frictional strength of Etnean gouges? The fault systems are indeed juxtaposing different lithologies and, to date, there are no information collected on the frictional properties of the Etnean lithologies projected to be there. With the aim of investigating the response of the Etnean gouges in static and dynamic friction of Etnean, a novel direct shear rig has been designed to suit the triaxial apparatus used in this research project. The direct shear holders proved to be a valuable technique to investigate the frictional properties of the gouges. Of the selected lithologies, the frictional strength is showing a dependence on clay content (e.g. decreasing frictional strength at increasing clay content), and an overall strain hardening behaviour.

Date of Award	2020
Original language	English
Awarding Institution	University of Leicester
Supervisor	Richard Walker (Supervisor), Philip Benson (Supervisor) & Audrey Ougier-Simonin (Supervisor)