The role of silicic magmas in crust formation: A case study of Iceland

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This project is carried out within the overall framework of "Iceland Cooperative Studies", a program which focuses on crustal formation as a result of interactions between the Iceland plume and the mid atlantic ocean. Our project addresses the role of silicic magmatism in the generation of Icelandic crust. We aim to determine the relative amounts of silicic and basaltic magma formed, and the origin of the silicic magmas (e.g., from magma differentiation and/or crustal remelting?). Our preliminary studies have found that the relative proportion of silicic magma erupted on Iceland has been significantly underestimated, primarily due to inadequate estimates of tephra volumes. The volume of silicic magma erupted at Iceland has major implications for determing local magma production rates and the amounts of residual plagioclase-rich cumulates within the Icelandic crust. We therefore plan to 1)reconstruct the volume and the history of silicic magmatism at Iceland since the Last Glacial period, 2) evaluate the relative importance of magmadifferentiation versus crustal remelting in local silicic magma generation, and 3) establish a relationship between tectonic setting and genesis of silicic rocks. We will use volcanological, petrological and geochemical methods to investigate represantative central volcanic systems on Iceland. We will focus on systems in differing tectonic settings, which are characterized by variable magma production rates and compositions.A compilation of the composition and volume of differentiated magmas erupted from each of these volcanic systems during the Holocene (the last 10.000 years) will be established through literature records of eruptions, local stratigraphic studies, and correlation of these with tephrostratigraphic records from the North Atlantic region. We will use these results to constrain average magma production rates for Iceland during the Holocene.