Pressure–temperature evolution of retrogressed kyanite eclogites, Weinschenk Island, North–East Greenland Caledonides

Caledonian eclogites and associated high-pressure rocks are present in a 400×100-km long belt along the coast of North–East Greenland. Kyanite and clinozoisite eclogites on Weinschenk Island (77°54′N, 21°17′W) occur as lenses within amphibolite facies, quartzofeldspathic gneisses. The eclogites have been extensively overprinted by lower pressure assemblages and exhibit a variety of coronitic and symplectitic reaction textures that record the exhumation path of the rocks. Textural relationships and mineral composition data indicate that the initial high-pressure, plagioclase-free assemblage was garnet+omphacite±kyanite±clinozoisite+rutile. Compositional growth zoning in garnet, together with distribution of mineral inclusions within it, record a prograde evolution from epidote–amphibolite facies progressing into the eclogite facies. Post-peak pressure reaction textures include clinopyroxene–plagioclase intergrowths after omphacite; the replacement of kyanite by sapphirine–plagioclase, spinel–plagioclase and corundum–plagioclase symplectites; and resorption of garnet by amphibole–plagioclase kelyphites. The replacement textures indicate that post-eclogite facies decompression took place while the rocks remained at elevated temperatures (upper amphibolite/granulite facies conditions). The metamorphic evolution of the eclogites is in agreement with eclogite formation by thick-skinned crustal imbrication and subhorizontal shortening of the Laurentian margin during Caledonian collision, exhumation to amphibolite facies by emplacement of the eclogite-bearing thrust sheet on the Laurentian margin and accompanying erosion, and final exhumation to the surface by post-Caledonian crustal thinning.