Bonjour à tous,
Je vous annonce l’organisation d’un VolcaPot vendredi 21 octobre 2016 à 14h en salle de séminaire.
Nous accueillerons Sam Poppe du département de Géographie de Vrije Universiteit Brussel (VUB), Belgique.
Sa présentation portera sur : An unusual patient : imaging analogue experiments of volcanic intrusions using X-ray Computed Tomography
Magma plumbing systems below volcanic edifices are complex. They consist of diverse elements through which the magma is transported to its final position in the shallow crust as a magmatic intrusion, or to the surface to feed volcanic eruptions. Through field examples from the Comoros archipelago, we observe complex magmatic intrusion geometries in the shallowest part of eroded volcanic plumbing systems. Analogue experiments have been used to simulate intrusion processes in a laboratory environment, and study intrusion geometries, as well as model surface deformation. Nevertheless, we rely on volcano and laboratory monitoring techniques to constrain the ground surface deformation during natural or simulated magma intrusion events, and are physically incapable of directly observing the mechanics and dynamics of an ongoing injection of magma below the earth’s or model surface.
During recent years, X-ray computed tomography (XCT) has made important technological advances, making it possible to scan patient-size objects in less than one second at resolutions of few tens to hundreds of micrometers. In this presentation, we report a characterisation of the geomechanical properties of sand-filler mixtures, and show amongst others, that their behavior is rather complex compared to the purely brittle Mohr-coulomb behavior commonly desired by the dimensional scaling laws that govern the force balance in analogue geo-models. We then characterise the X-ray absorption for a range of rock and magma analogues. Finally, we demonstrate how such thorough characterisation methodology led to full 4D (3D + time) imaging of cone sheet intrusion experiments, allowing both to observe analogue intrusion growth and structural deformation in the model interior and surface.