Frontier exploration and the North Atlantic Igneous Province: new insights from a 2.6 km offshore volcanic sequence in the NE Faroe-Shetland Basin

摘要

The Lagavulin exploration well 217/15-1Z penetrated a c. 2.6 km thick volcanic sequence dominated by extrusive basaltic rocks spanning the Paleocene-Eocene boundary in the NE Faroe-Shetland Basin. The well comprises one of the thickest drilled sequences through the North Atlantic Igneous Province. Integrated analysis of drill cuttings and wireline-log data reveals key volcanic lithofacies: (1) tabular lava flows; (2) compound lava flows; (3) hyaloclastite; (4) volcaniclastic rocks. The volcanic facies reveal two major sub-aqueous to subaerial sequences consistent with lava delta progradation. These sequences are separated by a volcanic hiatus represented by extensive reddened soils, which preceded the re-submergence of the area. Emergence followed by submergence of the first lava delta is interpreted to record an intra-T40 transient uplift event near the Paleocene-Eocene boundary. Basalts from the lower c. 1.3 km have low TiO2 (<1.5 wt%) and low Zr/Y (2-3), with olivine-phyric picrites towards the base (Mg# 70-82; olivine Fo(85-91)). The hiatus correlates precisely with a change to high-TiO2 (2.5-3.2 wt%), high-Zr/Y (>4) compositions, which dominate the upper sequence. The associated change in lava geochemistry, transient uplift and volcanic hiatus appears consistent with a transient pulse of hot buoyant plume material passing beneath the area.