Plume-Ridge Interaction: a Geochemical Perspective from the Reykjanes Ridge

Plume–ridge interaction in the Reykjanes Ridge and Icelandregion is graphically demonstrated by several V-shaped ridgessurrounding the spreading axis, indicating mantle flow awayfrom Iceland. It also has significant geochemical effects. Regionally,incompatible element concentrations increase northwards coincidingwith decreasing depth and increasing crustal thickness, depthof melting and proximity to Iceland. Major and trace elementdata show that isolated magma bodies feed individual volcanicsystems along the ridge. Fractionation within these systemsincreases towards 60–61°N, where it coincides withthe intersection of a V-shaped ridge, thicker crust and moreabundant seamounts. Trace element, Nd and Sr isotopic data revealdynamic melting and mixing within a southward-thinning, heterogeneousmantle wedge beneath the Reykjanes Ridge. Melting is variableand locally enhanced at 58°N, 59°N, 60°N and 61°N.A total of six mantle components are identified. Some are specificto Iceland whereas others are found only beneath the ridge axis.The geographical distribution of these components reflects theirorigin within the deep upper and lower mantle and subsequenttranslation by plume outflow along the entire length of theridge. KEY WORDS: plume–ridge interaction; Iceland; Reykjanes Ridge; dynamic mantle mixing and melting