TY - BOOK

T1 - Thermochemical structure of the Earth's mantle and continental crust

T2 - Insights from a multidisciplinary approach involving seismological, mineral physics, geodetic and petrological constraints

AU - Guerri, Mattia

N1 - Ph.d.-grad opnået ved mundtligt forsvar 9. september 2016

PY - 2016/8/1

Y1 - 2016/8/1

N2 - A detailed knowledge of the Earth's thermal structure and chemical composition is fundamental in order to understand the processes driving the planet ormation and evolution. The inaccessibility of most of the Earth's interior makes the determination of its thermo-chemical conditions a challenging task. In this thesis, I adopt a multidisciplinary approach geared towards the unification of geochemical and geophysical constraints within a framework provided by theoretical and experimental mineral and rock physics. In the first part, I focus on the Continental crust, assessing the relations between elastic properties and chemical composition taking into account the thermal and pressure effects. I found that even small amounts of H2O have an extremely high impact on the elastic properties of crustal rock. In addition, I show the potential that modifications in the stable mineralogical assemblage have in determining crustal seismic discontinuities. In the second chapter, I deal about the possibility to disentangle the dynamic and isostatic contribution in shaping the Earth's surface topography. Dynamic topography is directly linked to mantle convection driven by mantle thermo-chemical anomalies, and can be therefore used as a constraint regarding the mantle thermo-chemical structure. In the thesis I highlight thefact that the modelling of the isostatic component of topography is affected by uncertainties large enough to hamper a clear detection of the dynamic effects. Furthermore, residual topography maps (obtained as the difference between observed topography and computed isostatic component) and dynamic topography maps (computed through mantle flow modelling), that theoretically should both represent the effect of mantle convection on surface topography, present instead a low correlation coefficient. I argue therefore that our understandings of the lithosphere density structure, needed to determine the isostatic topography, and of the mantle density and viscosity, required to compute the dynamic topography, are still too limited to allow a robust determination of mantle convection effects on the Earth's topography.

AB - A detailed knowledge of the Earth's thermal structure and chemical composition is fundamental in order to understand the processes driving the planet ormation and evolution. The inaccessibility of most of the Earth's interior makes the determination of its thermo-chemical conditions a challenging task. In this thesis, I adopt a multidisciplinary approach geared towards the unification of geochemical and geophysical constraints within a framework provided by theoretical and experimental mineral and rock physics. In the first part, I focus on the Continental crust, assessing the relations between elastic properties and chemical composition taking into account the thermal and pressure effects. I found that even small amounts of H2O have an extremely high impact on the elastic properties of crustal rock. In addition, I show the potential that modifications in the stable mineralogical assemblage have in determining crustal seismic discontinuities. In the second chapter, I deal about the possibility to disentangle the dynamic and isostatic contribution in shaping the Earth's surface topography. Dynamic topography is directly linked to mantle convection driven by mantle thermo-chemical anomalies, and can be therefore used as a constraint regarding the mantle thermo-chemical structure. In the thesis I highlight thefact that the modelling of the isostatic component of topography is affected by uncertainties large enough to hamper a clear detection of the dynamic effects. Furthermore, residual topography maps (obtained as the difference between observed topography and computed isostatic component) and dynamic topography maps (computed through mantle flow modelling), that theoretically should both represent the effect of mantle convection on surface topography, present instead a low correlation coefficient. I argue therefore that our understandings of the lithosphere density structure, needed to determine the isostatic topography, and of the mantle density and viscosity, required to compute the dynamic topography, are still too limited to allow a robust determination of mantle convection effects on the Earth's topography.

UR - https://soeg.kb.dk/permalink/45KBDK_KGL/fbp0ps/alma99121975943005763

M3 - Ph.D. thesis

BT - Thermochemical structure of the Earth's mantle and continental crust

PB - Department of Geosciences and Natural Resource Management, Faculty of Science, University of Copenhagen

ER -