Aragonite, as an inclusion in olivine from a leucitite lava flow, provides evidence for high-pressure crystallization and carbonatitic activity beneath the geophysical lithosphere in Calatrava, Spain. The aragonite occurs as a single crystal within olivine (Fo87), interpreted to have crystallized from a carbonated silicate melt at mantle depths. Experimental data constrain the stability of aragonite to depths of >100 km at CO2-H2O-bearing mantle solidus temperatures. This is the first documented evidence of magmatic aragonite crystallized in the mantle. Entrained as xenocrysts, the olivines have not crystallized from the carrier melts, which must have formed deeper within the mantle. Lead isotope data of the leucitite and carbonate inclusions indicate that the source melts show isotopic enrichment relative to mid-oceanic ridge basalt and most ocean island basalt. Our evidence strengthens the argument for direct and deep mantle-derived volcanic carbonatite in alkaline volcanic provinces containing maar-type volcanism, such as Calatrava.