8 - HP and UHP eclogites and garnet peridotites in the Scandinavian Caledonides

Summary

Abstract

A review of the high and UHP eclogites and garnet peridotites from the Scandinavian Caledonides concerning models of their formation provides a background for individual descriptions of the various localities. The structure of the Scandinavian Caledonides is dominated by an assembly of thrust sheets transported eastward and finally emplaced on the Baltoscandian Platform during the Scandian Orogen in the Middle to Late Silurian. The tectonic units can conveniently be divided into five major complexes, the autochthon (and parautochthon), the lower, middle, upper and uppermost allochthons. Eclogites and eclogitic rocks are found within several of the tectono-stratigraphic levels of the Scandinavian Caledonides. Eclogites within the autochthon/parautocthon include rocks of the Proterozoic Western Gneiss Region, Traena Island, and the Lofoten-Vesterälen area. Eclogites within the Middle Allochthon include the Bergen Arcs and in the Hardangervidda-Ryfylke Nappe complex. The eclogites within the Upper Allochthon include the Seve Nappes. Eclogites within the Uppermost Allochthon are from the Tromsø Nappe Complex. Critical mineral assemblages are discussed for each locality along with known data on the age of metamorphism, and in some cases fluid inclusion studies provide new insights. Garnet peridotites within the Scandinavian Caledonides are present within Proterozoic basement Gneisses of the Western Gneiss Region of Norway and the Sev Nappe Complex in northern Sweden. Thermobarometric and geochronological data on occurrences of relict UHP mineral assemblages are given for Mg-Cr type peridotite bodies at a number of localities, mostly in the coastal region of the Western Gneiss Region.