Excessive magmatism in the North Atlantic area in Early Paleogene times (especially from ~62 Ma to ~50 Ma) generated vast expanses of mainly “flood basalts” in wide geographical areas [1] . Current manifestations of this magmatism are evident in areas including West Greenland (Disco and neighbouring areas), East Greenland (Scoresby Sund - Kangerlussuaq - Blosseville Coast areas), NW parts of the British Isles (NW Ireland and in the Inner Hebrides), submerged areas off West Norway (Vøring and Møre highs areas), submerged areas of the Rockall Plateau (mostly western parts) and the Faroe Islands. Collectively, these regions are most often referred to as the North Atlantic Igneous Province (NAIP) [2] [3] .

The pre-rift North Atlantic area consisted of an ancient crust, which to a large degree represented terranes residual from the closure of the Iapetus Ocean, some of which originated from different settings from either side of the closing ocean being more or less juxtaposed. In the course of complex and discontinuous extension/rifting, segments of this crust became isolated on all sides and now occur as sunken sub-oceanic micro-continents or terranes, which in places are overlain by Early Paleogene basaltic crust. Current offshore areas in the North Atlantic known to harbour such ancient “sunken” continental crust in the North Atlantic include the “Faroe Islands - Rockall Plateau micro-continent” [4] - [6] , the “Jan Mayen micro-continent” [7] , terranes beneath the Vøring- and Møre highs offshore West Norway [8] and possibly also a micro-continent below present-day Icelandic basalts [9] .

Accordingly, initial melts, which gave rise to Early Paleogene basaltic magmas of the NAIP travelled from their sources in the upper mantle and ascended through materials comprised of either basaltic oceanic crust or through more silica-rich continental crust of various thicknesses according to geographical location, while en-route to the Earth’s surface. In the latter case, contamination of basaltic magmas with continental crustal materials can sometimes be detected geochemically, thus enabling researchers to ascertain geochemical compositions of crustal contaminants to some degree. However, relatively small amounts of crustal contaminants in basaltic melts are often hard or impossible to detect geochemically. In such cases, measurements using isotopes such as Strontium (Sr), Neodymium (Nd) or Lead (Pb) can sometimes reveal even small crustal contaminants in basaltic magmas, as these occur in much larger concentrations in parts of the continental crust, when compared to sources to basaltic magmas in the upper mantle [10] .

In this study, Pb isotopic compositions (²⁰⁶Pb, ²⁰⁷Pb and ²⁰⁸Pb normalised against ²⁰⁴Pb) in Early Paleogene basaltic rocks from a few sills of the Faroe Islands are contrasted against basaltic materials from the NW fringes of the Hatton Bank of similar ages and against continental materials from more silica-rich and much older basement materials of the Rockall Bank, in order to assess if isotopic relationships exist between any of these.

The Faroe Islands Basalt Group (FIBG), which forms a relatively central part of the NAIP, rests on an up to ~30 km thick stretched continental basement (a sunken micro-continent) [4] . The Early Paleogene Faroese lava pile, which had an original thickness of ~6.6 km or more can be grouped into 7 formations of various thicknesses and makeup [12] . The 3 uppermost formations of these are intruded by a few basaltic saucer-shaped sills of various sizes ( Figure 1 ). Some of the latter can be grouped according to similarities in geochemical compositions, isotopic make-up and similarities in ages [11] [13] . Examples include the two segments of the Streymoy Sill and the Kvívík Sill, the two segments of the Eysturoy Sill and the Sundini Sill, while other intrusions such as the Morskranes Sill display distinct ages, geochemical and isotopic compositions.

Parts of the Rockall Plateau are covered by widespread Early Paleogene basaltic lavas, which have been emplaced from large central igneous complexes and widespread fissures. Continental basement rocks crop out in relatively restricted parts of the Rockall Bank and the Hatton Bank [6] . The latter is thought to be made up of metamorphic terranes (gneisses and slates) overlain by sandstones and shale in places [6] , while more detailed investigations of the geochemistry and petrography of selected basement materials from the Rockall Bank have revealed that these were of granulitic and granitic compositions [14] .

As no continental basement is exposed onshore the Faroe Islands, the one way to detect geochemical or isotopic compositions of such materials is by means of basaltic rocks, the initial melts of which may have been contaminated by the sub-basaltic continental crust they traversed, while ascending to the local lava successions from the upper mantle. A few silica-rich “presumably contaminated” basaltic horizons within the Faroese lava successions with silica (SiO₂) contents of 53 - 54 weight percent (Faroese basaltic rocks display silica contents of ~49 weight percent on average), which also appear to be much enriched in Sr, Nd and Pb isotopes, have been reported previously [15] [16] . As such, these could potentially be utilised to assess the geochemical and/or isotopic make-up of the Faroese sub-basaltic basement, as has indeed been attempted earlier [13] . However, preliminary results from recent own investigations (unpublished) seem to suggest that these samples could in reality be sedimentary specimen originating from within the local basaltic rocks, thus rendering them unsuitable for the actual purpose. Other possibilities include Faroese sills ( Figure 1 ), which are not noticeably enriched geochemically, but which do display moderate isotopic diversities [13] . Here, the geochemically and temporally identical high-TiO₂ Eysturoy and Sundini sills, the geochemically and temporally identical low-TiO₂ Streymoy and Kvívík sills and the LREE depleted Morskranes Sill in particular are of noticeable significance.

In this contribution, selected isotopes representing these 3 Faroese sill groups are compared/contrasted against continental basement samples reported for the Rockall Bank [14] and Early Paleogene basalts reported for the NW fringes of the Hatton Bank [17] [18] ( Figure 2 ). To be more detailed, Pb isotopes representing

5 basement samples from the Rockall Bank, 12 basaltic samples from the NW fringes of the Hatton Bank and 11 samples from 5 Faroese sills combined, are utilised in order to assess potential mutual relationships between any of these ( Figure 3 ). As there are no noticeable differences between configurations of ages corrected back to Early Paleogene times versus actual measured lead isotope data, measured data are used in this work.

When it comes to Pb isotopes for basaltic samples of the NE fringes of the Hatton Bank, the noticeable spread within these may suggest moderate heterogeneities within their mantle source(s) in general, while the substantial overall elongated configurations of the plotted samples combined towards larger ²⁰⁷Pb values strongly point to contamination with a crustal continental source enriched in ²⁰⁷Pb isotopes, potentially with Pb isotopic characteristics comparable to some of those measured for the Rockall Bank, or with a specific Hatton Bank basement even more enriched in ²⁰⁷Pb ( Figure 3 ). Researchers from an earlier isotopic study on the Hatton Bank basalts came to roughly similar conclusions [18] .

With respect to the actual Faroese basaltic materials, the 2 samples from the geochemically identical Eysturoy and Sundini sills display identical Pb isotope compositions despite being sampled ~10 km apart, indicating a homogeneous common mantle source for both of these, but also suggesting insignificant or no crustal contamination. The geochemically identical Streymoy and Kvívík sills, which were collected a few kilometres apart, differ chiefly in their ²⁰⁷Pb isotope contents, indicative of either slight heterogeneities in their mantle source(s) or (more likely) of crustal contamination. In the latter case, a sub-basaltic basement contaminant, displaying Pb isotope compositions broadly similar to some of those measured for the Rockall Bank, would be an obvious candidate ( Figure 3 ). The 7 samples representing the Morskranes Sill, which were mostly collected a few tens to a few hundred metres apart, display clear evidences of crustal contamination with respect to their ²⁰⁷Pb isotopes. Sub-basaltic basement contaminants, displaying Pb isotope compositions broadly similar to some of those measured for the Rockall Bank would be obvious candidates. Alternatively, sub-basaltic crustal contaminants even more enriched in ²⁰⁷Pb isotopes than the crust of the Rockall Bank, perhaps a potential specific Hatton Bank type basement, could be invoked as a candidate for the ²⁰⁷Pb enrichments of Faroese basaltic rocks. After all, many of the Hatton Bank basaltic samples display a more or less direct continuation from samples of the Faroese Morskranes Sill when it comes to their ²⁰⁷Pb isotope compositions ( Figure 3 ).

In this short contribution (Review Paper), emphasis has been put on the detection of potential relationships between various rock suites of the North Atlantic area, including Early Paleogene basaltic rocks of the Faroe Islands versus contemporaneous basaltic rocks of the Hatton Bank area (i.e. on the Rockall Plateau) and Faroese sub-basaltic continental crust versus continental crust exposed on the Rockall Bank (i.e. on the Rockall Plateau). In order to achieve both of these objectives, lead isotopes, measured previously for these regions, have been employed. The results are twofold: i. The results point to a potential relationship between Faroese basaltic rocks in general and those measured for the Hatton Bank, ii. the lead isotopic composition of one of the selected contaminated Faroese sills in particular suggests a likely link/connection between the Faroese sub-basaltic continental crust and continental crust of the Rockall Bank and hence the Rockall Plateau.

The Faroese isotope data stem partly from a PhD project carried out at Durham University, United Kingdom (Defended primo January 2012), financed by BP, Chevron og Geysir Petroleum, while the rest of Faroese lead isotope data were financed privately.

The author declares that there are no conflicts of interests involved in the production of this “review” paper.