The Mesoproterozoic cratonization of Baltica - New age constraints from SW Sweden
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Comparable early Mesoproterozoic tectonic histories resulted in the formation of 1.71-1.62 Ga Labradorian and 1.75-1.55 Ga Gothian crust in Laurentia and Baltica respectively, along a postulated contiguous margin. New U-Pb geochronology in southwest Sweden has constrained the timing of three consecutive stages of the Gothian Orogeny. Calc-alkaline magmatism, presumably related to subduction, occurred as late as 1587 ± 3 Ma, indicating convergence and consumption of oceanic crust until this time. These magmas intruded terranes of previously accreted arcs, thus providing a minimum age for their juxtaposition and accretion. The age of the latest stage of Gothian migmatization is constrained between 1555 ± 2 and 1553 ± 2 Ma, synchronous with the transition from ductile to brittle conditions at the presently exposed erosional level. This transition permitted the emplacement of a suite of mafic-felsic 1555-53 Ma intrusions during an extensional regime that may have coincided with the post-deformational collapse of the Gothian Orogen. These age refinements in southwest Sweden indicate that the final stage of the Gothian Orogeny in Baltica occurred considerably later than that of the Labradorian Orogeny in Laurentia. The preservation of Gothian-aged titanite from southwest Sweden indicates that post-Gothian metamorphism, including that of Sveconorwegian-Grenvillian age, was not penetrative in this region.
|Book series||Geological Society Special Publication|
|Number of pages||13|
|Publication status||Published - 1996|