From May 2018 to the end of 2021, Mayotte (Comoros Archipelago) experienced an important volcanic event that emitted 6.5 km³ of almost aphyric (<5 wt. % crystals) evolved basanitic magma, leading to the construction of an offshore volcanic edifice (Fani Maoré), 50 km east of Mayotte. Thermobarometric constraints, using olivine and clinopyroxene crystals, suggest that the eruption was fed by two reservoirs located at relatively deep mantle conditions (≥37 km); these being in close agreement with the depths of the volcano-tectonic seismicity recorded during the eruption. The evolved basanite exhibits a dominant mineral assemblage consisting of magnesian olivine (Fo70) and titanomagnetite, seemingly formed at sub-surface levels. Yet few crystals are characterized by reversal zoning (Fo55 to Fo70) and ilmenite cores mantled by titanomagnetite, their presence suggesting interaction of the main basanite with an evolved magma at 17±6km. These constraints point to a plumbing system characterized by magma storage at varying depths. However, thermobarometric estimates have large uncertainties in terms of pressure (100–400 MPa) and temperature (±50°C). Based on these observations, we conducted crystallization experiments using a piston-cylinder apparatus at 0.65–1.3 GPa and 1050–1100°C to explore magma storage depths and intensive conditions (H2O + CO2, ƒO2) of Mayotte basanite. The experimental olivine compositions (Mg/Fe ratio) confirm a strong dependence on pressure and temperature, allowing us to model storage conditions. The dominant mineralogy is best reproduced at 1075°C and P≤0.65-1 GPa (≤20-30 km), with H2O content >1.5 wt. % under reduced conditions (FMQ buffer). However, the ferrous olivines imply either a lower temperature (<1050°C) or a decreased water content to be formed at high pressure. Our experimental results, compared to thermobarometric constraints, indicates a main crystallization episode at deeper conditions (≤30 km) rather than a near-surface episode, providing key constraints on the magmatic plumbing system that fed this volcanic crisis.