On the Timing and Nature of Magmatism in the North Atlantic Igneous Province: New Implications from Basaltic Rocks of the Faroe Islands

In this contribution we present novel radiometric 40Ar/39Ar ages representing a number of basaltic sills/lavas of the Faroe Islands, which themselves form part of the North Atlantic Igneous Province. Measured ages are utilised in an attempt to assess the local igneous history, where the new ages are contrasted against those of other local rocks of known ages as well as against those of comparable/neighbouring North Atlantic igneous regions. The novel ages presented in this contribution allow us to put new constraints on the timing of late stage magmatic activity and associated crustal extension of this part of the North Atlantic area. In this research we present new ages as young as ~50.5 Ma for some of the smallest Faroese sills and demonstrate that the larger and oldest local sills, grouped into the low-TiO2 Streymoy/Kvívík sills and the high-TiO2 Eysturoy/Sundini sills respectively (~55.5 Ma), likely formed immediately subsequent to the formation of the uppermost parts of the Enni Formation, which itself represent the latest stages of local surface magmatism at ~55.8 Ma. Gradually decreasing sill volumes coupled with successively younger ages point to systematic decrease of local igneous activity with increasing distances to active contemporaneous local rifting zones. Comparable scenarios recorded for other parts of the North Atlantic Igneous Province support our inferences regarding the nature of late-stage magmatic activity at some distances from zones of active seafloor-spreading. Comparisons between ages of Faroese igneous products versus those of e. g. central E Greenland point to a somewhat diachronous evolution pattern within this part of the North Atlantic Igneous Province subsequent to ~57.5 Ma. The lithosphere-asthenosphere boundary is commonly thought to be critical for the formation of basaltic magmas. Accordingly, the close spatial and temporal associations between many high-TiO2 and low-TiO2 Faroese rock suites are interpreted in the context of a regional version of this boundary.