Eruptive history and 40 Ar / 39 Ar geochronology of the Milos volcanic 1 field , Greece 2 3

High-resolution geochronology is essential to determine the growth-rate of volcanoes, which is one of the key factors 7 to establish the periodicity of explosive volcanic eruptions. However, there are less high-resolution eruptive histories (>106 8 years) determined for long-lived submarine arc volcanic complexes than for subaerial complexes, since the submarine 9 volcanoes are far more difficult to observe than subaerial ones. In this study, high-resolution geochronology and major element 10 data are presented for Milos Volcanic Field (VF) in the South Aegean Volcanic Arc, Greece. The Milos VF has been active 11 for over 3 Myrs, and the first two million years of its eruptive history occurred in a submarine setting that has emerged above 12 sea level nowadays. The long submarine volcanic history of the Milos VF makes it an excellent natural laboratory to study the 13 growth-rate of a long-lived submarine arc volcanic complex. This study reports twenty-one new high-precision 40Ar/39Ar ages 14 and major element compositions for eleven volcanic units of the Milos VF. This allows us to refine the volcanic evolution of 15 Milos into nine phases and five volcanic quiescence periods of longer than 200 kyrs, on the basis of age, composition, volcano 16 type and location. Phase 1-5 (~3.34-1.60 Ma) contributed ~85% by volume to the Milos VF, whereas the volcanoes of Phase 17 6-9 only erupted small volumes (2-6 km3 in DRE) rhyolitic magmas. Although there are exceptions of the felsic cone volcanoes 18 of Phase 1-2, in general the Milos VF becomes more rhyolitic in composition from Phase 1 to Phase 9. In particular, the last 19 three phases (Phase 7-9) only contain rhyolites. Moreover, the high-resolution geochronology suggests that there are at least 20 three periods of different long term volumetric volcanic output rate (Qe). In the Milos VF, the Qe varies between 0.2 and 21 6.6Í10-5 km3.yr-1, 2-3 orders of magnitude lower than the average for rhyolitic systems and continental arcs. 22