Geochemical Stratigraphy and Correlation within the Faroe Islands Basalt Group: Temporal and Spatial Evolution of Mantle Sources during Continental Rupture

The geochemical signatures recorded during periods of Large Igneous Province (LIP) volcanism provide important evidence as to mantle sources and magmatic evolution through time. Our understanding of the temporal development of these provinces relies on both accurate stratigraphical sampling constraints of flood basalt sequences along with the integration of available age-dating methods. In this contribution we present new major, trace and mineralogical element data for the Faroe Islands Basalt Group (FIBG), NE Atlantic. The FIBG records a near continuous ~6.6km composite eruptive succession of the Palaeogene aged North Atlantic Igneous Province. All the data is stratigraphically constrained within a GIS database and has been compared to biostratigraphic and sedimentary inter-bed geochemical data which allows high resolution inference into the timing of eruption events during continental rupture. Distinct mantle source variations occur at a number of intervals through the stratigraphy including N-MORB-like and enriched ‘Icelandic’ sources. The integration of the new flow by flow data for the lower Beinisvørð and upper Enni Formations helps constrain the timing and the nature of these transitions. A distinct transition from Nb-depleted N-MORB-like to a Nb-enriched ‘Icelandic’ source is recorded in the last few flows of the first major phase of FIBG volcanism. This transition immediately precedes the regional hiatus recorded by the Prestfjall Formation before renewed N-MORB-like source volcanism. The timing of this hiatus, directly after the short lived onset of ‘Icelandic’ source volcanism implies a potential link between magma plumbing and tectonic reorganisation at the time. The Enni Formation at the top of the FIBG encompasses at least two inter-digitating flow fields sourcing separate high-TiO₂ enriched sources and a low-TiO₂ MORB-like source. The distribution of distinct geochemical lava groups on the Faroe Islands are demonstrated to overlap both in space and time. The present results have important implications to correlation attempts involving lava geochemistry on both the local and regional scale.