Structural Studies in the Western Part of the Skellefte District, Northern Sweden

Abstract

Structural studies in the W part of the Skellefte district have given some new facts about the orogenic movements in this area. There are at least two generations of cleavage in the Kristineberg area caused by stresses perpendicular to them. The direction of stress has turned through 30° in a clockwise direction between the two folding stages. A third stage of deformation connected with the Revsund granite and with a stress almost at right angles to the stresses of the former stages is probable but signs of it are rarer.

Dragfolds at the contacts of the Rudtjebäcken ore show that the ore was intruded in a highly viscous state moving towards SE in relation to the wall rocks above and below. The ore emanations were evidently dewatered and concentrated during their ascent upwards in the dome. At the time of emplacement the ore was a mixture of sulphide crystals and a hydrothermal solution which acted as a lubricant. Drag-folds on the flanks of the dome indicate that it formed by cross folding. The angle between the stresses of the first and last deformations is almost a right angle in this area, too.