Hotspots, Large Igneous Provinces, and Melting Anomalies

Abstract

This chapter describes the progress that has been made over the past decades in understanding observations of large-scale melting anomalies that are not readily explained by plate tectonic theory. Fundamental observations include the volume and geochemistry of flood basalts and ocean island basalts, the age progression of volcano chains, the geometry of hotspot swells, and the seismic imaging of crust and mantle structures. Observations of a subset of melting anomalies can be explained by classical plume theory, in which buoyancy-driven upwellings rise through the entire mantle to cause massive flood basalt volcanism that is trailed by an age-progressive hotspot volcano chain. However, a range of observations call for significant extensions to classical theory, and some sites of excess volcanism are better explained by alternative mechanisms, such as small-scale convection or shear-driven upwelling, than by plume theory. Detailed studies of upwelling and melting can provide constraints for heat and material fluxes through the mantle and provide a better understanding of the long-term thermal and chemical evolution of the Earth's interior