The Rb—Sr age of the Ursand granite on the boundary between the Åmål and “Pregothian” mega-units of southwestern Sweden

Abstract

The Rb-Sr age of the Ursand granite massif is 1250 ± 50 m.y. Within the limits of experimental error, this is identical with the Rb—Sr age of the Hästefjorden massif, situated close to the central axis of the Åmål mega-unit in south-western Sweden. The age determination confirms that granites of the Hästefjorden group transgress the limits between the Åmål and “Pregothian” mega-units. It also suggests that this event of granite formation has regional significance in parts of the south-western Baltic Shield.