Title of the talk: Bulldozering dykes in the ductile crust – Observations from Sarek national park in northern Sweden.
For a volcano to erupt, magma must propagate through the earth’ crust from a magma reservoir at depth to the surface. The most fundamental pathway for transport of magma is through sheet intrusions referred to as dykes. These sheet intrusions are generally thought to propagate like a fracture by tensile opening of their tips and elastic bending of the host rock. A growing number of observations in the geological rock record, however, suggest that other mechanisms contribute to how sheet intrusions are emplaced. One such mechanism assumes that the tip of the sheet intrusion pushes the host rock, which in turn deforms by inelastic processes. This mechanism appears to be particularly important where the host rock is weak. To document the contribution from inelastic processes during dyke emplacement we conducted fieldwork in Sarek national park in Sweden, which displays a now eroded deep section of a rifted Ocean-Continental transition intruded by hundreds of dykes. This presentation will show observations from fresh outcrops in high alpine glacial cirques, which provide nearly 100% exposure over relatively large distances of the dyke complex and its host rock. The contact between the sheet intrusions and the host has been mapped in detail at several localities and for different types of host rock and show that the host rock is locally deformed in a manner which is non-compatible with large scale regional deformation trends.
Short bio: Hans Jørgen is a researcher specializing in volcanic plumbing systems at Njord, University of Oslo (UiO). He earned his Ph.D. from the Center for Earth Evolution and Dynamics (CEED) at UiO in 2019, where he explored the exposed deep sections of an ancient magma-rich rifted continental margin. During his Ph.D. fieldwork, he had the opportunity to study a dyke complex emplaced at the brittle-ductile transition in the crust, analyzing how igneous intrusion geometries were affected by the hot ambient conditions during emplacement. His current research builds partially on the results from his Ph.D., focusing on dyke emplacement in the ductile crust.
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