| dc.description.abstract | The Earth’s mantle transition zone (MTZ), located between approximately 410-660 km depth, can store an amount of water equivalent to 2-10 oceans of water, which is transported into the deep mantle by subducting oceanic lithosphere. The presence of water is likely to reduce the viscosity of mantle rocks and has the potential to generate melting in the upper mantle that could promote the occurrence of intraplate volcanism (IPV). Therefore, water within the Earth’s interior impacts mantle convection dynamics, plate tectonics and could alter the chemical and thermal evolution of the planet. Despite its importance, the amount and spatial distribution of water within the mantle, and its effect on the origin of volcanism far from plate boundaries, are poorly constrained. Previous modeling studies have estimated rates and volumes of water subducted into the deep mantle based on plate tectonic reconstructions that track the history of subduction through time. In this work, I extend this approach to model the spatial and temporal heterogeneity of water in the MTZ during the past 400 million years (Myr) and compare the predicted regions of wet and dry MTZ with the locations of past and present IPV. I conduct a parametric study where I vary the residence time of water in the MTZ, the slab sinking rate, and the delay period between water in the MTZ and IPV occurrence. Despite the uncertainties associated with the plate tectonic reconstructions and IPV dataset, my models show a remarkable agreement between the hydrated regions of the MTZ and locations of IPV. I find a statistically significant correlation at the 95% confidence level for models where 60-89% of IPV locations occur above wet regions of the MTZ during the past 250 Myr. This confirms the hypothesis that water is transported to the MTZ by subducting slabs and, consequently, causes spatial and temporal mantle heterogeneities. Furthermore, my results show that the MTZ water residence time significantly impacts the distribution of water, with the best fits obtained for residence times of 100 Myr or longer. This implies that MTZ water reservoirs caused by the dehydration of stagnating slabs can remain stable for time periods much longer than the sinking time of a slab. In contrast, the effect of varying the vertical descent rate of slabs and the IPV delay period is modest. However, a delay of 10-50 Myr between water in the MTZ and intraplate eruptions better predicts IPV locations than accounting for no delay. Overall, these findings suggest a link between the formation of volcanism far from plate boundaries and water within the MTZ. | eng |