Prolonged storage of supervolcanic magma revealed by titanium diffusion in plutonic K-feldspar

Supereruptions, which discharge >450 km3 of magma, are among Earth’s most extreme volcanic events. Although their eruptive phases are brief (days to years), the buildup and storage of silicic magma reservoirs can span millions of years. These reservoirs typically exist as crystal-rich mushes that may be thermally reactivated, sustaining long-term eruption potential. However, direct constraints on their longevity, especially from intrusive records, remain scarce, limiting our ability to assess the long-term volcanic hazards. Here, we constrain the minimum lifespan of a silicic magma reservoir by modeling titanium (Ti) diffusion in K-feldspar megacrysts from early Eocene quartz monzonites linked to the Pangduo supereruption in the southern Tibetan Plateau. X-ray fluorescence mapping and trace element analyses reveal reverse Ti zoning indicative of mafic recharge. Diffusion chronometry constrains the interval between the final pre-eruptive recharge and reservoir solidification to >100−1000 k.y. Thermal modeling demonstrates that recharge-induced reheating can maintain upper-crustal magma temperatures (>800 °C) over comparable durations. These findings provide direct evidence from plutonic rocks that near-eruption silicic reservoirs can persist for hundreds of thousands of years, thereby bridging short-term volcanic signals with long-term storage inferred from intrusive records.