Melting predictions in Geodynamic Models with emphasis in Edge-Driven Convection
- Doctoral Thesis
Rights / licenseCreative Commons Attribution 4.0 International
Intraplate volcanism is a widespread but poorly understood phenomenon because it is a process which is not readily explained by plate tectonics. In the Eastern Atlantic, several volcano groups are located near the continental margin, e.g. the Canaries, Cape Verde, etc; but the origin of this activity remains poorly understood. The two main hypotheses put forward to explain these islands involve mantle-plume activity and Edge-Driven Convection (EDC). One way to discriminate between these two models is the systematic exploration and analysis of geodynamic numerical models. Geodynamic models enable experimentation in the Geosciences at otherwise inaccessible temporal and spatial scales. To test and constrain these models, careful comparison of model predictions with geological, geochemical and geophysical observations is required. However, quantitative comparison of geochemical signatures remains restricted, because thermodynamic models such as pMELTS are not optimized for coupling with geodynamic codes. In turn, simplified and robust parameterizations of mantle melting so far are not designed to provide any output of magma geochemistry. In the following dissertation, I address two main research problems: (1) the suitability of EDC to generate major mantle melting and to support the formation of volcanic islands in the eastern Atlantic; and (2) the development of a melting parameterization that is capable of predicting melt major-element compositions in geodynamic models. The first question is addressed in chapters 2-4, while the second is developed in chapter 5. Using a comprehensive 2D modeling study, I find that EDC alone is insufficient to produce the magma volumes required to sustain major island-building volcanism. EDC occurs in all our models, in which a continental "edge" of lithospheric thickness is imposed. However, it remains highly transient and can feed only little-to-no melting at the base of mature oceanic lithosphere. To further understand the origin of major island-building volcanism near continental edges, we study the effect of EDC on mantle plumes (chapter 4). I find that EDC can deflect mantle plumes with small-to-moderate buoyancy flux and modify the magmatism generated. Indeed, the amount, geometry and chemistry of mantle melting are sensitive to the distance of the plume from the edge. However, they are also controlled by intrinsic plume properties such as temperature and buoyancy flux. Show more
External linksSearch via SFX
ContributorsExaminer: Tackley, Paul J.
Examiner: Ballmer, Maxim Dionys
Examiner: Gerya, Taras V.
Examiner: Gazel, Esteban
Examiner: Shorttle, Oliver
Organisational unit03698 - Tackley, Paul / Tackley, Paul
MoreShow all metadata