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

Plume-ridge interaction in the Reykjanes Ridge and Iceland region is graphically demonstrated by several V-shaped ridges surrounding the spreading axis, indicating mantle flow away from Iceland. It also has significant geochemical effects. Regionally, incompatible element concentrations increase northwards coinciding with decreasing depth and increasing crustal thickness, depth of melting and proximity to Iceland. Major and trace element data show that isolated magma bodies feed individual volcanic systems along the ridge. Fractionation within these systems increases towards 60-61°N, where it coincides with the intersection of a V-shaped ridge, thicker crust and more abundant seamounts. Trace element, Nd and Sr isotopic data reveal dynamic melting and mixing within a southward-thinning, heterogeneous mantle wedge beneath the Reykjanes Ridge. Melting is variable and locally enhanced at 58°N, 59°N, 60°N and 61°N. A total of six mantle components are identified. Some are specific to Iceland whereas others are found only beneath the ridge axis. The geographical distribution of these components reflects their origin within the deep upper and lower mantle and subsequent translation by plume outflow along the entire length of the ridge.