Constraining the influence of a LIP on the Neoproterozoic break-up of Baltica and Laurentia

The supercontinent Rodinia broke up in the late Neoproterozoic to form the oceans and margins separating paleocontinents such as Baltica, Avalonia and Laurentia, which in turn later collided to form the Caledonian - Appalachian mountain belts. Some of the geological products of the complex evolution from passive-margin- to break-up are presently found in nappe complexes within the Scandinavian Caledonides. The break-up was associated with emplacement of major dolerite dike complexes of Ediacaran age (c. 600 Ma), probably constituting a pre-Caledonian Large Igneous Province. The dominantly doleritic dike swarms intruded a thinned continental crust comprising both crystalline basement and marine sediments deposited in pre- to early syn-rift. During peak rifting a sheeted dike complex defining the ocean-continent transition (OCT) evolved. More than 100 Myr later, during early stages of plate convergence, distal parts of the margin and the OCT experienced high to ultra-high pressure metamorphism, before the remnants of the dike swarms and the OCT were finally thrusted onto Baltica as nappe complexes and are thus exposed in the Scandinavian Caledonides. The best-preserved parts provide a remarkable analogue to present day OCTs and adjacent areas that generally only is observable in seismic sections. In order to understand the dynamics of the continental break-up, we will investigate the exposed areas to better constrain the active mechanisms that eventually produced oceanic crust. This presentation reports on `research-in-progress' and we expect to present new results from systematic photogrammetry, including 3D model(s) of dike swarm geometries. Observations from the study area suggest that there are several generations of dikes, which possibly are related to an evolution of the stress field during magma emplacement. Detailed work in progress on the metamorphic petrology and geochronology (TIMS and SHRIMP) will be used to better constrain the P-T conditions during emplacement of the dikes as well as later eclogitization and to better characterize the Proterozoic basement rocks into which the break-up related dikes were emplaced.