Age of the Krossnes Granite, West Norway

Abstract

Rb-Sr isotope whole-rock dating of the Krossnes Granite has yielded an isochron age of 430 \u00B1 6 Ma with I.R. = 0.07066 \u00B1 0.0005, interpreted as the age of intrusion. This age is close to that of the Håkre Granite of the Sunnhordland Batholith, to which the Krossnes Granite is probably related. The age indicates that the Krossnes Granite probably intruded during the period of deposition of the Ashgillian-Llandoverian sediments of the Ulven and Holdhus Groups, Major Bergen Arc. It also demonstrates that strong ductile deformation of rocks in the Major Bergen Arc occurred during the Ordoviician or close to the transition from the Ordovician to the Silurian periode.