Comparación de los Complejos Intrusivos de Jörn y Viterliden en el distrito minero de Skellefte, norte de Suecia

Abstract

The Skellefte Mining District is located in the northern Sweden, in an early Proterozoic (1.90-1.87 Ga) volcanic arc province in the Baltic Shield. It is composed by a complex submarine volcanosedimentary succession named Skellefte Group overlain by shallow- to deep-marine sedimentary rocks and mafic volcanics named the Vargfors Group, at the top occurs a subaerial felsic volcanic succession named the Arvidsjaur Group (Allen et al., 1996). Among the intrusions in the area, the Jörn Granitoid Complex (JGC) and the Viterliden Intrusive Complex (VIC) are the most significant and crops out in the central and westernmost area of the Skellefte district respectively. Both complexes emplaced at similar ages and igneous rocks are similar in bulk composition. Also, they show similar relationships with the Skellefte volcanics, as in both cases early plutonic phases are coeval with volcanics whereas late plutonism postdates the Skellefte group. In contrast, JGC and VIC markedly differ in deformation and metamorphic style. We show that the metamorphism in the JGC is mainly static, whereas the VIC is related to regional deformation producing intense ductile deformation. Also, a number of mineral phases, including amphiboles, distinctly differ in composition from the Jörn to the VIC area. We conclude that metamorphism in the VIC and the JGC occurred in contrasting tectonic settings