Structure and metamorphism of the Tången—Inviken area, Seve Nappes, Central Scandinavian Caledonides

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Abstract
The Tången-Inviken area extends across the whole width of the Seve Nappes. In the Seve Nappes two major units have been recognized, corresponding to the Central and Eastern Belts described elsewhere. The metamorphic grade of the Central Belt is upper amphibolite-to granulite-facies; that of the Eastern Belt is lower/middle amphibolite facies. A tectonic contact is inferred to be present separating these units. Eclogitc bearing gneisses are found in the Central and Eastern Belts; they form megascopic lenses which are bounded on each side by inferred tectonic contacts. One of these contacts is truncated by the overlying basal Köli thrust, indicating several stages of thrusting. The metamorphic evolution of the eclogitc-bearing tectonic lenses, in both the Central and Eastern Belts, differs from that of the sequences elsewhere in the Seve Nappes: (1) In the tectonic lenses high pressure mineral assemblages are converted into intermediate pressure mineral assemblages during virtually isothermal uplift. (2) Outside the tectonic lenses the early metamorphic evolution of the rock sequences is solely characterized by intermediate-pressure mineral assemblages. A palinspastic reconstruction of the high pressure Seve rock units supports depression of the Baltic plate underneath the Greenlandian plate during a Himalaya type of continent-continent collision.