Eruptive history and ⁴⁰Ar∕³⁹Ar geochronology of the Milos volcanic field, Greece

Abstract

High-resolution geochronology is essential for determining the growth rate of volcanoes, which is one of the key factors for establishing the periodicity of volcanic eruptions. However, there are less high-resolution eruptive histories (> 106 years) determined for long-lived submarine arc volcanic complexes than for subaerial complexes, since submarine volcanoes are far more difficult to observe than subaerial ones. In this study, high-resolution geochronology and major-element data are presented for the Milos volcanic field (VF) in the South Aegean Volcanic Arc, Greece. The Milos VF has been active for over 3 Myr, and the first 2 × 106 years of its eruptive history occurred in a submarine setting that has been emerged above sea level. The long submarine volcanic history of the Milos VF makes it an excellent natural laboratory to study the growth rate of a long-lived submarine arc volcanic complex. This study reports 21 new high-precision 40Ar/39Ar ages and major-element compositions for 11 volcanic units of the Milos VF. This allows us to divide the Milos volcanic history into at least three periods of different long-term volumetric volcanic output rate (Qe). Periods I (submarine, ∼ 3.3–2.13 Ma) and III (subaerial, 1.48 Ma–present) have a low Qe of 0.9 ± 0.5 × 10−5 and 0.25 ± 0.05 × 10−5 km3 yr−1, respectively. Period II (submarine, 2.13–1.48 Ma) has a 3–12 times higher Qe of 3.0 ± 1.7 × 10−5 km3 yr−1. The Qe of the Milos VF is 2–3 orders of magnitude lower than the average for rhyolitic systems and continental arcs.