Structures and ore genesis of the Grimsdalen deposits, southern Trondheim region, Norway.

Abstract

The central part of the Grimsdalen area of the southern Trondheim region is occupied by a sequence of metavolcanics with subordinate metasediments, termed the Folla Group, which are correlated with the Støren Group of the central and western parts of the region. The Folla Group is thrust above arkosic sparagmites and is itself overthrust by metasediments of the Mesæterhø Group. A tectonic model for the Grimsdalen area, which has been affected by two major phases of deformation, is presented. The sulphide deposits of the area occur in a single pyritite horizon within the Follo Group, and 4 ore types have been differentiated. The metamorphic evolution of the pyritite and the different generations of pyrite are discussed in relation to the structural and metamorphic history of the Folla Group sequence.