Publication: Modelización físico-numérica 2D y 3D de procesos de subducción. Influencia de las características de las placas superior e inferior y de la interacción con el flujo mantélico
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2013-05-27
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Universidad Complutense de Madrid
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Abstract
La dinámica del hundimiento de litosfera en las zonas de subducción ejerce un control importante en la evolución del sistema manto-placas tectónicas. En consecuencia, se han desarrollado durante las últimas décadas una gran cantidad de estudios centrados en diferentes tipos de observaciones, así como en modelización analítica, en laboratorio y numérica. Sin embargo, algunos aspectos importantes del proceso de subducción aún no se comprenden bien, como es el caso de la contribución relativa de los diferentes factores que causan la variabilidad observada en los ángulos de subducción. Por ejemplo, cabría esperar que la litosfera joven, y por tanto relativamente caliente y poco densa, causara una flotabilidad negativa pequeña y en consecuencia su buzamiento fuese menor. Sin embargo, esto contrasta con el elevado buzamiento de la litosfera joven de la placa de Cocos bajo Centroamérica. Además del torque gravitacional asociado a la flotabilidad de la laja (slab), interviene un torque de succión hidrodinámica generado por el flujo inducido en la cuña mantélica (entre el techo de la laja y la base de la placa superior). Este torque tiende a succionar la laja hacia arriba y disminuir su buzamiento. El balance entre estos torques controla el buzamiento resultante de la laja. Como punto de partida de este trabajo, se hipotetizó que el estado térmico de la placa superior debía ejercer un importante control sobre la estructura de viscosidad en esta cuña, y por tanto sobre el torque de succión hidrodinámica.
The dynamics of sinking lithosphere at subduction zones has a strong control on the evolution of plate-mantle system. Accordingly, a large number of studies focusing on observational data, as well as analytical, laboratory and numerical models have been developed during the last decades. However, some important aspects of subduction process remain poorly understood, such as the relative contribution of different factors causing the observed variability of slab dip. While the effects of overriding plate thickness on slab dip and on trench motion have been recently studied by means of 2D modeling, a systematic analysis of the effect of overriding plate thermal state has not been performed before this thesis. In the present study, 2D and 3D numerical thermo-mechanical modeling were developed to obtain a better understanding of the dynamics of subduction, and to explore different factors that might play an important role in controlling the geometry of the slab and associated mantle flow. The finite element method was applied to solve the coupled equations of mass, momentum and energy conservation for an incompressible fluid. In Chapters 3 and 4, 2D numerical models of kinematically-driven subduction using the commercial software Comsol Multiphysics were developed. Modeling results indicate that plates subducting underneath cold overriding plates are predicted to subduct with lower slab dip, and this effect is predicted to be more important and persistent than that of the subducting lithosphere age.
The dynamics of sinking lithosphere at subduction zones has a strong control on the evolution of plate-mantle system. Accordingly, a large number of studies focusing on observational data, as well as analytical, laboratory and numerical models have been developed during the last decades. However, some important aspects of subduction process remain poorly understood, such as the relative contribution of different factors causing the observed variability of slab dip. While the effects of overriding plate thickness on slab dip and on trench motion have been recently studied by means of 2D modeling, a systematic analysis of the effect of overriding plate thermal state has not been performed before this thesis. In the present study, 2D and 3D numerical thermo-mechanical modeling were developed to obtain a better understanding of the dynamics of subduction, and to explore different factors that might play an important role in controlling the geometry of the slab and associated mantle flow. The finite element method was applied to solve the coupled equations of mass, momentum and energy conservation for an incompressible fluid. In Chapters 3 and 4, 2D numerical models of kinematically-driven subduction using the commercial software Comsol Multiphysics were developed. Modeling results indicate that plates subducting underneath cold overriding plates are predicted to subduct with lower slab dip, and this effect is predicted to be more important and persistent than that of the subducting lithosphere age.
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Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Física de la Tierra, Astronomía y Astrofísica I (Geofísica y Meteorología) (Astronomía y Geodesia), leída el 30/01/2013