Intraplate magmatism, serpentinization and hydrothermal venting in the ultra-slow spreading setting of the Eurasia Basin, Arctic Ocean

The Eurasia Basin, one of two major oceanic basins of the Arctic Ocean, is composed of the Amundsen and Nansen basins, which were created due to the slow and ultra-slow seafloor spreading at the mid-oceanic Gakkel Ridge initiated during the Paleocene-Eocene transition (53-56 Ma). Since the beginning of the current millennia the Gakkel Ridge and the Eurasia Basin have been subject of marine geological and geophysical studies leading to the collection of diverse datasets including rock samples, seismic, and potential-field datasets. New marine seismic data has become available in the western Eurasia Basin in the very last years, including data acquired by the Norwegian Petroleum Directorate in the context of the UN Law of the Sea, together with seismic lines gathered by Norwegian research institutions and partners. During October-November 2022 the first High Arctic GoNorth marine expedition collected new seismic reflection and refraction, as well as gravity and magnetic datasets. It is considered that this polar region may hold important clues for the understanding of global processes such as passive margin formation, and the complex links between plate tectonics and climate. Volcanic additions have been suggested within the flanks of the Eurasia Basin during different stages in the Cenozoic. Existing hypotheses further postulate corridors of exhumed mantle formed across the western Eurasia Basin because of the magmatic segmentation imposed by the Gakkel Ridge. Consequently, the oceanic basement of this area should be prone to deformation, hydrothermal alteration and serpentinization. However, little is known about the relationships between such processes with the sedimentary units above, or whether such processes occur away from the ridge and to what extent.

The new compilation of multi-channel seismic reflection profiles provides an image of the sedimentary structure and the upper crust, within the oceanic crust and the continent-ocean transition (COT) between northern Svalbard margin and Eurasia Basin. The preliminary analysis of these datasets indicates that the sediments and basement structures within the southwestern corner of the Eurasia Basin have been modified in a unique manner due to an underlying geothermal anomaly beneath the lithosphere. This is expressed as focused late Miocene (< 20 Ma) to recent sill intrusion events resulting in basement and sediment deformation, and intense hydrothermal and sediment evacuation features. We present unique examples of hydrothermal venting on seismic reflection data and discuss implications of the post-rift NE Atlantic and Arctic setting, including the role of breakup magmatism, post-breakup intraplate volcanism, and sheared/passive margin development during the Cenozoic.