Rapid emplacement of a Palaeogene silicic volcanic centre, Arran, western Scotland

The timing and duration of silicic magmatism at relatively small volcanic centres in the geological record remain poorly constrained but are vital for understanding the temporal evolution of magmatic provinces. The Palaeogene Central Arran Igneous Complex (CAIC), and the nearby North Arran Granite, show spatial and temporal relationships between silicic intrusions and intra-caldera volcanic deposits. High-precision UPb zircon geochronology, integrated with detailed field observations, allows a timeline of silicic magmatic activity on Arran to be constrained. Silicic magmatism in north and central Arran occurred as a very short-lived (∼0.5 Ma) ‘pulse’ during the protracted (>8 Ma) evolution of the British Palaeogene Igneous Province (BPIP). Evolution of the CAIC volcano from caldera collapse to eruption of the youngest preserved unit (including several phases of eruption punctuated by quiescent periods of land surface erosion and deposition of sediments) took no more than 185 ka. Silicic magmatism at the complex (volcanism followed by intrusion of granites) lasted no more than 330 ka, with the North Arran Granite was emplaced shortly prior to the CAIC. This evidence of a short magmatic pulse accompanied by drastic land-surface changes has major implications for our understanding of localised silicic magmatism in other igneous provinces, both in the geological record and the present day.