Iceland geochemical anomaly: Origin, volcanotectonics, chemical fractionation and isotope evolution of the crust

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Abstract
Iceland is an oceanic plateau produced by channeled flow from the Iceland hotspot. The Icelandic rift system moves WNW relative to the hotspot. About magnetic anomaly 7 time the rift system overrode the hotspot from the east, and since that time the south segment of the Eastern Rift Zone of Iceland has kept position over the hotspot by the initiation of new spreading centers at its east margin. As a result, the volcanism across Mid‐Iceland reworks old crust of the hotspot trail. The Iceland geochemical anomaly is the result of magmatic processes within a chemically layered crust. That layering results from the kinematics of crustal accretion in the rift zones where material, hydrated in the zeolite facies, is brought down into the amphibolite facies where partial melts are formed and separated from the subsiding material. Assimilation of crust‐derived partial melts into ascending mantle‐derived olivine tholeiites is a feedback process resulting in the accumulation of large ion lithophile elements in the crust. That process is most extensive in silicic volcanic centers. The evolution of high 87Sr/86Sr ratios and low 143Nd/144Nd ratios in Iceland reflects long standing accumulation of Rb and light rare earth elements in the crust. The reworking of the hotspot trail, both along the southward propagation of the opening rift in south Iceland and along the eastward migration of the rift segment above the hotspot, involves regeneration of extinct volcanic centers. That process accounts for the observed increase in the 87Sr/86Sr ratio of intraplate centers as they are drifted away from their parental rift zones and for high ratios observed in silicic centers ahead of the propagating rift in south Iceland.