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Authors: Spang, Arne
Advisor: Kaus, Boris
Title: Thermomechanical modeling of magmatic systems
Online publication date: 17-Aug-2022
Language: english
Abstract: Magmatic systems and their volcanoes shape the lives of hundreds of millions of people around the globe. As these transcrustal systems cannot be directly observed, their structure and internal processes can only be inferred by modeling them and comparing the results to surface observations. Limited by computational cost, traditional models had to neglect structural complexity, magma buoyancy and realistic rheologies. This results in an inability to enhance the understanding of the large scale dynamics and evolution of magmatic systems. Estimating the onset, duration, magnitude or type of volcanic eruptions remains unfeasible. This thesis introduces new numerical modeling approaches to magmatic system research to tackle the existing challenges and utilize the growing number of surface observations more effectively. That includes a new parameterization for complex three- dimensional (3D) shapes which facilitates treating the initial model geometry as a flexible input parameter. With this approach, uncertainties of constraints on the initial geometry of the geological setting can be taken into account and the sensitivity of different observations to the initial geometry can be tested. By combining the new parameterization with a massively parallel thermomechanical model, gravity forward modeling, petrological modeling and a set of different surface observations, the large scale geodynamics of the Altiplano-Puna magma system in the central Andes are investigated. The study includes a complex-shaped partially molten zone (magma body), magma buoyancy and visco-elasto-plastic rheology as it is observed in real rocks. Average density, melt content and geometry of the magma body are constrained alongside the key material parameters that govern the dynamics of the system. While traditional models attribute surface uplift to intrusion, this model demonstrates that it can also be caused by buoyancy-driven material transport within the magma body. The last part of the thesis investigates the effect of the presence of pre-exsolved volatiles on syn-eruptive subsidence. A scaling law is derived that predicts subsidence as a function of volatile density, volume and depth as well as crustal rigidity. Applying the derived scaling law to the 2015 eruption of the Chilean stratovolcano Calbuco shows that about 20% of the observed syn-eruptive subsidence can be attributed to the release of pre-exsolved volatiles. This thesis tackles several of the existing challenges that are associated with numerical modeling of magmatic systems. Structural complexity is addressed by utilizing a new parameterization for 3D shapes and high resolution models. Considering realistic, nonlinear rheologies and using high resolution, 3D models is facilitated by high- performance computing and a massively parallel thermomechanical software. The often neglected buoyancy of magma and volatiles in particular is incorporated as a driving mechanisms for magma dynamics. Finally, a joint interpretation of different surface observables provides much improved constraints on non-unique, sub-surface structures and processes.
DDC: 004 Informatik
004 Data processing
500 Naturwissenschaften
500 Natural sciences and mathematics
550 Geowissenschaften
550 Earth sciences
Institution: Johannes Gutenberg-Universität Mainz
Department: FB 09 Chemie, Pharmazie u. Geowissensch.
Place: Mainz
URN: urn:nbn:de:hebis:77-openscience-61081398-2925-4d89-b63a-f206d84b845c6
Version: Original work
Publication type: Dissertation
License: CC BY-SA
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Extent: xv, 117 Seiten, Illustrationen, Diagramme
Appears in collections:JGU-Publikationen

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