The South, Central, and North Atlantic margins are dominated by volcanic passive margins, which in turn constitute major portions of large igneous provinces (LIPs). The voluminous magmatism in each of these Atlantic segments is commonly attributed to mantle plumes: the Tristan, CAMP, and Iceland plumes respectively. However, despite the popularity of the plume concept, its validity is currently debated (www.mantleplumes.org). We are sceptical to a number of plume aspects and have investigated the possible relationship between Atlantic volcanic passive margins and reactivation of pre-existing late Neoproterozoic/Phanerozoic fold belts (referred to as Phanerozoic hereafter). The Atlantic margins are the least complicated passive margins to investigate for this purpose. A relationship has already been proposed between the Caledonian suture and the anomalous melt production at Iceland (Foulger, 2002). We have found evidence of a similar correlation for the greater Atlantic margins. Atlantic volcanic margin segments developed along reopened Phanerozoic sutures, while non-volcanic margins formed where: a) cratons were separated, b) Phanerozoic fold belts were transacted at a high angle, or c) Archean mobile belts were followed. Thus, it appears that the natural outcome of the Wilson Cycle, when applied to the reactivation of Phanerozoic belts, is volcanic passive margins.

It appears possible that the process behind volcanic margin development is strongly influenced by the protolith, perhaps more so than by spreading rates or elevated temperatures in mantle plumes as previously suggested (e.g. Bown & White, 1995, White & McKenzie, 1989). Remnants of eclogitized orogenic roots (Ryan & Dewey, 1997; Ryan, 2001) may provide a fertile source for melt generation (Yaxley, 2000). Tectonically unroofed eclogites, from lower portions of the Caledonian Orogen, are well known in the Western Gneiss Region, SW Norway (e.g. Austrheim, 1987). Eclogites are found throughout the Caledonian-Appalachian Orogen (e.g. Steltenpohl et al., 2003) as well as in the Mauritanides, and more sparsely in the Pan-African fold belts. Other factors that can be of importance for the volcanic margin development are build-up of heat beneath the Pangean supercontinent prior to break-up, and edge-driven convection (King & Anderson, 1998).

A Middle Cretaceous LIP also characterizes the Arctic, where significant magmatism is well documented in the Sverdrup Basin, North Greenland, Svalbard, and Franz Josefs Land (Maher, 2001). Although we lack seismic refraction or reflection data from the margins of the Canada Basin, it appears plausible that its margins are volcanic. The c. 38 km thick oceanic crust of the Alpha Ridge (Weber & Sweeney, 1990) may be a subaerial volcanic construction. Bathymetric and magnetic data from the Arctic suggest that the Mendelev Ridge may be a complementary ridge to the Alpha Ridge. Together the two resemble the Greenland – Faroes Ridge. The Canada Basin can be argued to have utilized the Early Carboniferous Ellesmerian fold belt. Break-up of the non-volcanic Tertiary Eurasia Basin, on the other hand, was dictated by the strength of the pre-existing Canada Basin, and followed its shear margin (cf. Grantz et al., 1990). The Eurasia Basin does not appear to have cut across a major Phanerozoic fold belt, but rifted off a thin continental sliver (the Lomonosov Ridge) from the northern edge of the Barents Sea - Kara Sea Platform. Thus, it appears that the suggested relationship in the Atlantic also holds true in the Arctic.

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