Some aspects of the Precambrian in south-eastern Sweden in the light of a detailed geological study of the Lake Nömmen area

Abstract

The supracrustal rocks of the Lake Nömmen area of south-eastern Sweden comprise two groups, namely, the Lake Nömmen volcanic group and the sedimentary Björkö group. Both groups are included in the Vetlanda supergroup. The supracrustals were intruded by a complex of plutonic rocks dominated by granodiorites. The Rb/Sr isochron age of the granitoids is 1839 m.y. All these rocks are considered to be equivalent to the orogenic Svecofennian further north. The rocks belonging to the Småland plutonic and volcanic complexes are considerably younger. The geological evolution in this part of Sweden is discussed and five phases of deformation are proposed.