Fergus McNab , Patrick Ball

Quantifying the depths and temperatures from which igneous rocks are derived is an important step in understanding volcanic, magmatic and mantle processes. We present meltPT, a Python package that allows users to apply twelve published whole-rock thermobarometers within a consistent framework, as well as combine thermobarometric results and geothermal models to estimate mantle potential temperatures. We apply meltPT to basaltic rocks from mid-ocean ridges and the Hawai'ian Islands. We find mid-ocean ridge basalts equilibrate between 1-2 GPa and 1275-1475 oC, corresponding to an ambient mantle potential temperature of ~1400 oC. We estimate that the Hawai'ian plume has an excess temperature of ~150 oC. Hawai'ian melt-equilibration depths increase from 1-3 GPa to 2.5-5 GPa through each island's life cycle. Our results indicate that multiple lithologies are present within the plume, and that transient plume reconfiguration in response to changing plate velocity is a viable mechanism for generating Hawai'i's two geochemically distinct plume tracks.