Zu Hülle, Inhalt, Gefüge und Alter des Alkaligesteinsvorkommen von Norra Kärr im südlichen Mittelschweden

Abstract

An earlier published paper by the writer dealing with the alkali rock occurence of Norra Kärr has been commented on by v. Eckermann. Some misunterpretations and misunderstandings in his remarks will be discussed here. Some recent and clarifying data on the composition (four chemical rock analyses), the petrofabrics and age relations of the surrounding rocks are presented. The mineralogy, petrofabrics and tectonics of grennaite, the dominating alkali rock of the district is described in some detail. The persistent s and B fabrics of the grennaite are compared to those of the surrounding rocks, and the question of “Einströmungs-gefüge” or “Amplatzgefüge” is considered. The K-Ar-ages of grennaite and “surrounding Gothian acid rocks” given by v. Eckermann are discussed with regard to field relations.