Caledonian migmatization in central Nordaustlandet, Svalbard

On the island of Nordaustlandet, northeastern Svalbard, a Grenvillian-age basement complex is overlain by Neoproterozoic to Cambrian sedimentary rocks. Both early Neoproterozoic (c. 950 Ma) and Caledonian (c. 410 Ma) granites have been recognised in the area. Migmatites, spatially associated with the granites, have been variously interpreted to be of Precambrian or Caledonian age. New studies of the stratigraphy, structure, metamorphism and migmatization show that the intensity of Caledonian tectonothermal activity increases from west to east across Nordaustlandet. Migmatization of the lowermost metasedimentary units of the Neoproterozoic Murchisonfjorden Supergroup occurred in the vicinity of Innvika and was followed shortly thereafter by intrusion of Caledonian granites. Ion-microprobe (NORDSIM) analyses of zircons in two neosome samples of the migmatites indicate Caledonian migmatization.