Petrology Lunch - A new viscosity model for Colli Albani: study and implications of nanolites formation in the melt - Emanuele Fanesi

We are pleased to announce a Petrology Lunch with Emanuele Fanesi on the topic of: A new viscosity model for Colli Albani - study and implications of nanolites formation in the melt.

Abstract:

Explosive volcanic eruptions pose a significant threat, generating ash plumes up to 40 km in height and ejecting vast volumes of material (hundreds of km³) into the atmosphere. Recent eruptions highlight the critical need for robust volcanic hazard assessments. Magma rheology, primarily controlled by melt viscosity, dictates eruptive style. Relatively high viscosity limits outgassing, promoting magma fragmentation at depth thus explosive eruptions. Fe-Ti nanolite precipitation during ascent further increases viscosity by increasing melt polymerization and physically impeding flow. Viscosity models are crucial for understanding magma dynamics, enabling the estimation of melt viscosity at specific temperatures and compositions to model eruption behavior. However, the link between chemical composition and explosivity remains a subject of debate. Mafic-alkaline magmas are expected to erupt effusively, yet several volcanoes exhibit a history of mafic Plinian and Sub-Plinian eruptions. Here, we investigate the viscosity of tephri-phonolite magma from the Pozzolane Nere Plinian eruption (407 ± 4 ka) in the Colli Albani volcanic district. We propose a novel viscosity model for Colli Albani that incorporates the influence of Fe-Ti nanolite precipitation during magma ascent. Hydrous, nanolite-free glasses were synthesized from the Pozzolane Nere ignimbrite using a piston-cylinder apparatus. High-temperature viscosity measurements, Brillouin spectroscopy, and differential scanning calorimetry analyses were employed to parameterize the nanolite-free viscosity of Pozzolane Nere magma. Our findings indicate a lower viscosity for Pozzolane Nere magma at eruptive temperatures than previously thought, with important implications for magma ascent dynamics.

For Zoom link:

Meeting ID: 987 1824 7950

Passcode: 404131