South-East Greenland forms part of the North Atlantic Craton and is characterized by migmatitic orthogneisses, narrow bands of mafic granulite, ultramafic and possible meta-sedimentary rocks, and alkaline-carbonatitic intrusive rocks. Mafic granulite, meta-sedimentary and ultramafic rocks form the basement for the emplacement of granitic intrusions at ca. 2865Ma that lasted episodically until ca. 2790Ma and continuously during 2750-2700Ma. The area is structurally complex with evidence of at least seven deformation events including reclined and mushroom-like fold interference patterns. An older (>2790Ma) foliation formed in granitic rocks and the basement during the Timmiarmiut Orogeny (D T). Deformation associated with the ca. 2790-2700Ma Skjoldungen Orogeny folded this early foliation, and is associated with a penetrative foliation that is refolded progressively in a northeast-southwest oriented stress field. The orientation of the stress field progressively rotated into a northnorthwest-southsoutheast orientation during the last stages of the orogeny. The orogeny is also characterized by syn-deformational anatexis at granulite-facies (at approximately 800°C and 5-8kbar, ca. 2790-2740Ma), which decreased to the amphibolite-facies at ca. 2730Ma. The late- to post-tectonic granite and alkaline rocks assigned to the Skjoldungen Alkaline Province intruded the central-northern part around 2710. Ma. This was followed by north-south extensional deformation during the Singertat Stage forming discrete shear-zones at greenschist-facies grades, which is coeval with the emplacement of pegmatite, ijolite, and carbonatite emplacement during ca. 2680-2650. Ma. Similar lithology and tectonic processes in the Tasiusarsuaq Terrane of southern West Greenland and the Lewisian Complex in Scotland suggest a possibly large Archaean terrane at that time, which, taking the present size, at least covered around 500-600. km in an east-west direction and approximately 200. km in a north-south direction.
- Programområde 4: Mineralske råstoffer