Vulcan’s Secret: what volcanic compositions tell us about upper mantle dynamics

Basaltic lavas can record the pressure and temperature conditions under which they formed. Incompatible trace element ratios, in particular, are mostly unaffected by secondary processes occurring during magma ascent, so that they can yield useful information about the source region. Using examples from western North America and Australia, I will show how we can exploit of these properties through inverse modelling to derive lithospheric thickness and mantle potential temperature beneath intraplate volcanic provinces. At the present-day, this geochemical tool can be cross-validated using seismic observations of the same mantle properties. Since volcanic rocks are preserved from throughout Earth’s history, this method also allows us to look back in time and track the spatial and temporal evolution of the lithosphere-asthenosphere system.