Time and length scales of crust-magma interaction in rift settings

Abstract

Understanding the processes that lead to magma emplacement and differentiation in the crust is of fundamental importance to science and society, as these magma bodies are important components of crustal growth and erupted products. During magma emplacement and residence in the Earth’s crust, magma thermally and chemically evolves as a function of several complex nonlinear magmatic processes. This thesis work focuses on rift settings and quantifying the time and length scales involved in the thermal and compositional evolution of crustal magmas. In order to give quantitative constraints, this research utilizes a novel thermal-petrographic numerical model that solves for conservation of mass and energy in response to magma emplacement and extensional tectonic forces. In particular, this work tests the sensitivity of tectonic extension rates on crustal magma evolution. General trends of magma evolution are characterized in various rift systems. In particular, the numerical model is applied to Salton Sea Geothermal Field as a natural setting. This work delivers detailed insights to the interaction of magma and crust in extensional tectonic settings. The outcomes address important topics in volcanology including the timescales of generation of evolved magmas, and the thermal and compositional conditions that lead to the compositional diversity observed in diverse settings.