Temporal and spatial evolution of the Neogene age Breiðdalur central volcano through 39Ar/40Ar and U-Pb age determination

Abstract The volcanic sequences in eastern Iceland provide a cross-section of magmatic activity from the Iceland rift system throughout the Miocene. This study focuses on a high precision age determination campaign of a single Miocene volcanic system, the Breiðdalur central volcano and associated dyke swarm, in order to quantify its evolution. The central volcano consists of: a lower flank of mafic lavas erupted onto a basement of plateau basalts; an upper flank of intermediate and mafic lavas; an 8–10 km wide caldera with associated infill formations; and a summit sequence of lavas and tuffs. This study indicates that the central volcano had a lifespan of around 1 My, from 10.2–9.1 Ma, and started with mafic magmatism. Intermediate magmatism began around 10.04 Ma and the caldera formed between 9.8 and 9.5 Ma, evolving via multiple nested-caldera collapses. Effusive silicic magmatism was predominantly in the youngest sequences between 9.5 and 9.1 Ma. After 9.1 Ma the activity at the central volcano effectively ceased. The volcano became buried by plateau basalt sequences predominantly derived from eruptions at the associated Breiðdalur dyke swarm. Activity on the dyke swarm began around 9.9 Ma and continued to until 7.8 Ma, an additional 1.3 My.