Early Proterozoic crust-mantle interaction at a continental margin in northern Sweden

Abstract

Abstract On the basis of recent geochemical and Sm-Nd isotopic data, alternative models for the early Proterozoic evolution of the Archaean craton of the Baltic Shield and its marginal areas in northern Sweden are discussed. Before the deposition of a craton cover and the subsequent Svecofennian orogenic activity, the Archaean areas probably formed a continuous domain. The 1.89-1.86 Ga old early Svecofennian granitoids found close to exposed Archaean rocks were created largely by the remobilization of Archaean crust. To the south of the Archaean Domain, however, chronologically equivalent granitoids are made up of matter with short crustal residence times. That area, the Skellefte district, represents a new addition to the continental crust of the Baltic Shield ∼1.90 Ga ago. The particulars of the crustal accretion process are still controversial. However, recent data indicate different tectonic developments in the Skellefte district and in the vicinity of the Archaean-Proterozoic boundary farther north. Apparently, the one-time edge of the Archaean craton was situated somewhere between these two areas, but appears to have had a rather more northerly position than previously assumed.