TheTransscandinavian Igneous Belt (Swedish:Transskandinaviska magmatiska bältet), abbreviated TIB, is one of the majorlithological units of theBaltic Shield. It consists of a series ofbatholiths inSweden andNorway forming a ca. 1400 km long belt running fromLofoten, Norway, in the north toBlekinge, Sweden, in the south. The Transscandinavian Igneous Belt and its rocks solidified from magma between 1810 and 1650million years ago during theMesoproterozoic. The Transscandinavian Igneous Belt was likely formed in anAndean-type geological environment, implying it was once parallel to adestructive plate boundary.[1] The belt was first identified in the 1980s and was referred as the "Transscandinavian Granite-Porphyry Belt". The current name was first applied in 1987.[2]
The Transscandinavian Igneous Belt occurs as a ca. 1400 km long belt running fromLofoten in the north toBlekinge in the south.[3][4] The northern parts of the belt are partly covered byCaledoniannappes but crop out inwindows (e.g. Rombak, Nasafjället). In addition to this some Caledonian nappes are made up of Transscandinavian Igneous Belt rocks.[1] Beneath theEast European Platform the belt continues across the Baltic Sea to northeast Poland andKaliningrad Oblast.[5]
Theplutons of the belt formed variously between 1810 and 1650million years ago (Mya)[3] the oldest rocks overlapping in age with the rocks of theSvecofennian orogeny and the youngest overlapping in age with thedeformation andmetamorphism of theGothian orogeny.[6] Three separate periods of igneous activity are recognised in the Transscandinavian Igneous Belt; TIB 1 (1813–1766 Mya), TIB 2 (1723–1691 Mya) and TIB 3 (1681–1657 Mya). This grouping is not perfect as it excludes the youngest units formed 1450 million years ago.[4]
Hundreds of millions of years after the Transscandinavian Igneous Belt was formed it was subject to the particular deformation, tectonics and metamorphism of theSveconorwegian orogeny about 1100 to 990 million years ago.[3]
Characteristically thegranites and similar rocks of the Transscandinavian Igneous Belt are rich inalkali elements (e.g.sodium andpotassium) and haveporphyritictextures. Not all rocks of the Transcandinavian Igneous Belt have a pure alkaline character, some display chemistries tending to thecalc-alkaline magma series.[6] In addition to the above-mentioned rocks lesser amounts ofmaficintrusives are also part of the belt.[2]
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