Icelandia

Iceland, which is essentially unique on Earth, has more to offer than simply the opportunity to add detail to already existing theories. Iceland has long been interpreted in terms of a mantle high-temperature anomaly producing excess magmatism that happens to have a mid-ocean ridge passing through it. Many data cannot be easily interpreted in terms of this model, however. Perhaps the most persuasive evidence is that magma source temperatures fall well short of those necessary to generate the 30-40 km thick crust that, in the standard model, is assumed to be entirely magmatic. A plethora of other curious observations can only be explained in an ad hoc manner in the traditional model. We propose that the only way in which the observations can be easily and naturally accounted for is if the Icelandic lower crust is not predominantly magmatic but instead is magma-inflated, stretched, continental mid- and lower crust. This material has been emplaced by continuation of the process of continental volcanic margin formation that built the margins of the NE Atlantic ocean at the time of continental breakup. This process continued for an exceptionally long time at the latitude of Iceland and still has not yet completed. In our presentation we will summarize the evidence for this radical new idea and its extension to propose that stretched continental crust is widespread around Iceland and should be recognized as a new sunken continent called Icelandia. The theory has important implications for the study of volcanic margin formation because it implies that this process is currently ongoing in Iceland. If correct, it means that Iceland may be the only place on Earth where active volcanic margin formation can be studied. The theory is in need of evaluation through the collection of new, independent datasets that can test its predictions.