Geodynamical simulations underpin our understanding of upper-mantle
processes, but their predictions require validation against
observational data. Widely used geophysical datasets provide limited
constraints on dynamical processes into the geological past, whereas
under-exploited geochemical observations from volcanic lavas at Earth's
surface constitute a valuable record of mantle processes back in time.
Here, we describe a new peridotite-melting parameterization, BDD21, that
can predict the incompatible-element concentrations of melts within
geodynamical simulations, thereby providing a means to validate these
simulations against geochemical datasets. Here, BDD21's functionality is
illustrated using the Fluidity computational modelling framework,
although it is designed so that it can be integrated with other
geodynamical software. To validate our melting parameterization and
coupled geochemical-geodynamical approach, we develop 2-D single-phase
flow simulations of melting associated with passive upwelling beneath
mid-oceanic ridges and edge-driven convection adjacent to lithospheric
steps. We find that melt volumes and compositions calculated for
mid-oceanic ridges at a range of mantle temperatures and plate-spreading
rates closely match those observed at present-day ridges. Our
lithospheric-step simulations predict spatial and temporal melting
trends that are consistent with those recorded at intra-plate volcanic
provinces in similar geologic settings. Taken together, these results
suggest that our coupled geochemical-geodynamical approach can
accurately predict a suite of present-day geochemical observations.
Since our results are sensitive to small changes in upper-mantle thermal
and compositional structure, this novel approach provides a means to
improve our understanding of the mantle's thermo-chemical structure and
flow regime into the geological past.