Intraplate settings almost uniquely host alkaline magmas and carbonatites. Although these magmas are spatially connected, the petrogenetic link between alkali magmas such as ocean island basalts (OIBs) and carbonatites is not well established. While previous studies have sought to identify the source origin of these magmas, the mechanisms behind their differentiation remain poorly understood. To constrain the evolution of alkalic magmas at mid-lithospheric depths, we performed high pressure-temperature, phase equilibria experiments on a hydrous, CO2 rich mantle-derived partial melt composition. The experiments were conducted at 1.5-2.0 GPa and 1200-1500 °C. The experimentally generated samples were studied using electron probe micro-analysis, where phase assemblage consisted of olivine + clinopyroxene + spinel + carbonated-silicate melt ± calcite ± vapor. As the melt composition undergoes evolution, the initial stages of crystallization generate alkalic OIB-like compositions, which subsequently transition towards natural calcio-magnesio carbonatite compositions. Our findings suggest that a single volatile-rich parental melt composition can give rise to OIBs and carbonatites at varying conditions.