The Icelandic plume and its influence on the evolution of the NE Atlantic

The papers printed below were contributed by scientists who attended the second Arthur Holmes European Research Meeting held in Reykjavik, Iceland in early July 1994. The igneous rocks produced by mantle plumes and at seafloor spreading-centres provide a powerful probe for investigating the state of the mantle beneath the lithosphere. Iceland is a particularly good window into the convecting mantle because the North Atlantic spreading-centre crosses directly above the mantle plume: the plate divergence allows decompression melting to occur to depths as shallow as 15 km below the surface. In other mantle plumes, such as Hawaii, the thick lithospheric lid above the plume prevents the convecting mantle rising shallower than the base of the lithosphere which lies at a depth of many tens of kilometres. A further feature of the NE Atlantic is that decompression melting beneath the spreading centres adjacent to Iceland samples the asthenospheric mantle consistently at all distances from the mantle plume: this allows the spatial and temporal extent and variability of the plume to be investigated. The Arthur Holmes meeting was held early July 1994 in Reykjavik, Iceland, fittingly enough at a location almost on top of the European-North American plate boundary, and directly above the Iceland plume. The presentations covered six main themes: melt generation; the relative importance of plume, depleted mid-ocean ridge basalt and other magma sources; breakup processes and effects on marginal basins; the timing and expression of volcanic and tectonic events; and geochemical and geophysical manifestations of the plume through space.