The norito-granitic zone of Puntervoll-Lia (Rogaland anorthosite province, S. Norway): evolution of a genetic model

The norito-granitic zone is a thin septum of highly deformed banded rocks squeezed between two anorthosite massifs, the Egersund-Ogna (EGOG) and the Håland massifs. The dominant lithologies are a norito-anorthosite association gradationally passing into a norito-granitic association. A first genetic model was proposed in which a norite intruded in the foliated margin of the EGOG anorthosite was migmatitized and metasomatically transformed into an anorthosite. This model was not confirmed by later studies and finally the norito-anorthosite association was considered as a particular facies of the anorthosite margin. New studies of the Glypstad septum between EGOG and the Bjerkreim-Sokndal layered intrusion reveal that the norito-granitic association results from the deformation of a magma in which anatectic melts were mingled with a high-alumina basalt, parental to the EGOG anorthosite.