This body of research uses numerical models to investigate the dynamics of melt generation in the asthenosphere, accumulation at the base of the lithosphere by porous flow and subsequent infiltration into the lithosphere by dike propagation. Chapter 1 uses numerical models of melt migration in a viscously compacting matrix together with synthetic receiver function to show that the onset of melting in the asthenosphere can produce a seismic velocity gradient capable of generating a converted phase. To explain observed phases attributed to melting onset in regions with significant water in the mantle source, either (1) water is entrained as an initially dry plume passes through a hydrated transition zone or (2) the dependence of seismic velocity on melt fraction is much stronger than the standard relationship used in this study. Chapter 2 formulates a model for dike propagation from a partially molten boundary layer at the base of the lithosphere. Dikes propagate a short height into the lithosphere before freezing and a quasi-steady state boundary layer of high melt fraction can persist at the base of the lithosphere above regions of melt production. Chapter 3 investigates how melt intruding at the base of the lithosphere may influence the thermal and mechanical evolution of the lithosphere. Basal heating of the lithosphere by intruding dikes can rapidly thin the lithosphere on the order of tens of km/Myr, concentrating stress and triggering extension in the remaining lithosphere with little to no evidence of magmatic influence. The predicted time between extension onset and mantle lithosphere erosion matches the observed time over which strain accommodation in rift basins transfers from extension along border faults to magmatic accommodation. The calculated 2-D melt distributions seems consistent with the hypothesis that the negative velocity gradient observed near the base of the lithosphere in volcanic and extensional regions is caused by melt accumulating at its solidus.
Havlin, Christopher John,
"Dynamics of Melt-Lithosphere Interaction"
Earth, Environmental and Planetary Sciences Theses and Dissertations.
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