A large explosive silicic eruption in the British Palaeogene Igneous Province

• Published in: Scientific Reports
• Main Authors: Troll, Valentin R., Emeleus, C. Henry, Nicoll, Graeme R., Mattsson, Tobias, Ellam, Robert M., Donaldson, Colin H., Harris, Chris
• Format: Article in Journal/Newspaper
• Language: English
• Published: Nature Research 2019
• Subjects: North Atlantic
• Online Access: http://eprints.gla.ac.uk/174634/; http://eprints.gla.ac.uk/174634/1/174634.pdf

Large-volume pyroclastic eruptions are not known from the basalt-dominated British Palaeogene Igneous Province (BPIP), although silicic magmatism is documented from intra-caldera successions in central volcanoes and from small-volume ash-layers in the associated lava fields. Exceptions are the Sgùrr of Eigg (58.7 Ma) and Òigh-sgeir pitchstones in the Inner Hebrides (>30 km apart), which have been conjectured to represent remnants of a single large silicic event. Currently available major element data from these outcrops differ, however, creating a need to test if the two pitchstones are really related. We employ a systematic array of methods ranging from mineralogy to isotope geochemistry and find that samples from the two outcrops display identical mineral textures and compositions, major- and trace elements, and Sr-Nd-Pb-O isotope ratios, supporting that the two outcrops represent a single, formerly extensive, pyroclastic deposit. Available isotope constraints suggest a vent in the Hebridean Terrane and available radiometric ages point to Skye, ~40 km to the North. A reconstructed eruption volume of ≥5km3 DRE is derived, suggesting a VEI 5 event or larger. We therefore argue, contrary to long-held perception, that large-volume silicic volcanism and its associated climatic effects were likely integral to the BPIP during the opening of the North Atlantic.