The crystalline rocks of Germania Land, Nordmarken and adjacent areas, North-East Greenland

Abstract

The crystalline rocks of Germania Land, Nordmarken and adjacent areas are dominated by grey, migmatitic quartzo-feldspathic orthogneisses with a complex history of emplacement and deformation. Ultramafites, eclogites and metasedimentary rocks are preserved as inclusions or trails of enclaves within the migmatitic orthogneisses. Later intrusive suites include metadolerite dykes, alkali feldspar metaporphyries and metagabbros. All these crystalline rocks have suffered thorough metamorphism and deformation, and three fabric events are recognised. Three systems of late mylonite zones are found: west of the study area in Hertugen af Orleans Land, along the east side of Stormlandet and Germania Land, and in northern Store Koldewey and Lille Koldewey. The region lies within the East Greenland Caledonian fold belt. Available isotopic data suggest the crystalline rocks include Archaean and Early Proterozoic suites. These have undergone variable degrees of later reworking on several occasions. It is unclear how much of the deformation history is Caledonian and how much pre-Caledonian. The latest fault displacements are post-Caledonian, as shown by local preservation of fault bounded outcrops of Carboniferous and Jurassic sedimentary rocks.