Abstract
Subduction zones are dynamic systems that host significant natural hazards, such as seismicity and volcanism. These geologic processes are largely dependent on the thermal structure of the subduction zone, which evolves both over time and along the width of the subduction zone. The most direct constraints on slab temperatures and their variation across subduction zones worldwide comes from the global record of exhumed metamorphic rocks. This record also offers insights into the properties of the plate interface, including its viscous and frictional strength, deformation, and fluid release. Despite their importance, the mechanisms that bring to the recovery of exhumed rock from great depths remain debated. The timing of recovery, often punctuated, also varies across subduction zones, adding to the uncertainty surrounding its controls. This dissertation presents geodynamic modeling studies investigating the variability of both slab thermal structure and exhumation within oceanic subduction zones. In Chapter 2, we use 3-D subduction models to investigate how the temperature varies over the width of a 3-D subduction zone during the evolution of subduction. We find that the plate center is cooler than the edge during the early stages, while this trend reverses for mature subduction, consistent with natural observations. In Chapter 3, we show that 2-D, time-dependent subduction models, in which convergence rate varies with time, can match the punctuated nature of oceanic rocks exhumation. We find that exhumation is a discontinuous process throughout a subduction zone’s lifetime, governed by transient velocity changes and the plate interface rheology. Chapter 4 summarizes the key findings and outlines directions for future research.