Petrogenesis of post-glacial basalts from Snaefellsjökull, Iceland

Iceland is a unique geologic environment, lying at the intersection of mid-ocean ridge and a mantle plume. Large volumes of lavas are generated at rift zone, which are usually the focus of studies in Iceland. However, generous volumes of lavas are also generated away from rift zones, at flank zones, including the Snaefellsnes Peninsula in Iceland. Little decompressional melting occurs at flank zones, which are located away from the suggested plume center, so the mechanism for melt generation and transport has yet to be elucidated. The enriched component of the mantle is often preferentially tapped at the flank zones, so Snaefellsnes’s distance from the rift zones (40-170 km) and the suggested center of the plume (220-330 km) make it ideal to characterize the enriched component at Iceland. The Snaefellsnes flank zone is defined by three volcanic systems from east to west: Ljósufjöll, Lysuskard, and Snaefellsjökull. Broad east to west trends have previously been defined across the peninsula. This study presents new isotopic data, combined with previously published and unpublished elemental data, on lavas from Snaefellsnes, Iceland to provide new constraints on the composition and heterogeneity of the enriched mantle component beneath Iceland. New data from this study highlights important differences in the trace element composition between lavas from the Snaefellsjökull-Lysuskard and Ljósufjöll systems. Differences between Snaefellsjökull-Lysuskard and Ljósufjöll systems emphasize regional-scale heterogeneity in the enriched component beneath Snaefellsnes. Additionally, correlations of stable (oxygen) isotopes with radiogenic (Pb-Sr-Nd-Hf) isotopes and trace elements help to distinguish the source of the unique signature of Snaefellsjökull basalts.