Abstract

Abstract The time interval between the leptites and the intrusion of the urgranites was a period of strong volcanic action in the central and southern part of Sweden that was feed by the urgranite magma. The tuffs and lavas deposited were chiefly of quartzporphyritic composition. An exception is found in the Grythytte-Älvestorp syncline where rocks of this kind are lacking, probably on account of the absence of urgranite magma. This latter seems also to give an explanation of the very building of the syncline and the low grade of metamorphosis of the rocks in it. The biggest accumulation of quartzporphyrite material occurred in the present areas of migmatite gneiss.