Synchronized Mascarene volcanism reveals 400 kyr cycles in melt supply from the Réunion plume

Many hotspots display evidence of fluctuating magmatism through time, at periods of 1-20 Myr, reflecting variations in melt production and/or extraction within mantle plumes. Here we show that the Réunion hotspot exhibits ~10 times shorter fluctuations of magmatic activity. Using fieldwork, K-Ar geochronology, and geomorphology, we reconstruct the volcanic histories of Réunion and Mauritius, the youngest expressions of the Réunion hotspot. Our results reveal coeval phases of volcanic activity and repose on both islands over the past 3 Ma, with an average recurrence interval of 370 ± 202 kyr. Given the ~230 km separation between the islands and the heterogeneity of the underlying lithosphere, this large-scale volcanic synchronization is most consistent with quasi-periodic modulation of melt supply at mantle depths. The ~400 kyr timescale resembles the eruptive tempo of the Deccan Traps, suggesting that such short-period cyclicity may represent a long-lived characteristic of the Réunion hotspot.