Collaborative Research: Magma-Host Rock Interaction Processes of Assimilation in the Mid-Crustal Hortavaer Intrusive Complex, North Central Norway

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The 456 Ma Hortavar intrusive complex is part of the Caledonian-age Bindal Batholith in north-central Norway. It consists of alkaline rocks emplaced as hundreds or thousands of dike-like bodies into diverse host rocks (migmatite, quartzite, marble, and calc-silicate gneiss). The range of the igneous rocks, from olivine gabbro through syenite, their chemical variation, and their carbon isotope signatures indicates that the magmas assimilated calc-silicate and silicate rocks in situ. Recognition of in situ assimilation at Hortavar makes it an ideal place to address the mechanisms that control interactions between magmas and their host rocks in the middle crust: Are host rocks assimilated en masse? Or are solids assimilated according to their ability to dissolve in the magma undergoing contamination? Alternatively, are host rocks partly melted first, with only the melt component assimilated? We will use integrated field and microanalytical methods to test the hypothesis that carbonate + silicate assimilation was important during early magma evolution, but that silicate assimilation dominated later evolution. Because carbonate assimilation in a closed system is ineffectual, we will also test the likelihood that such assimilation occurred in an open system. The research will involve an international team of faculty and students. It will provide all participants with a rich, collaborative venture in new cultural and academic environments. It will also involve collaboration with scientists and students from the Norwegian Geological Survey and the Norwegian University of Science and Technology, and a local middle school teacher and amateur geologist.