Structural and petrological data along a transect across the Caledonian Fjord Region Detachment Zone in Andreè Land, North-East Greenland

• Main Author: Hauge, Kristina
• Other Authors: Arild Andresen og Deta Gasser
• Format: Master Thesis
• Language: English
• Published: 2013
• Subjects: VDP::450; Greenland; Grejsdalen; Hagar Bjerg; Kong Oscar Fjord; East Greenland; Kong Oscar fjord
• Online Access: http://hdl.handle.net/10852/37130; http://urn.nb.no/URN:NBN:no-38375

Field work for this thesis was conducted in Andreè Land, North-East Greenland Caledonides (73,35 N, 26,15 W), a region dominated by the Hagar Bjerg-Niggli Spids Thrust Sheet. The thrust sheet is composed of three main lithotectonic units from base upwards; 1) Paleoproterozoic ortho- and paragneisses, 2) the Late Mesoproterozoic Krummedal Supracrustal sequence, and 3) Neoproterozoic Eleonore Bay Supergroup, Tillite Group and the Late Cambrian to Ordovician Kong Oscar Fjord Group. The Krummedal sequence is intruded by c. 950 Ma granitoids, whereas c. 430-425 Ma granites are common in both the Krummedal sequence and the Lower Part of the Eleonore Bay Supergroup. The purpose of the study is to describe the main rock types and deformation structures in a transect through parts of the thrust sheet (Rendalen – Djævelkløften - Grejsdalen). The transect includes the lower and upper part of the Krummedal sequence and the lower part of the Eleonore Bay Supergroup. Particular focus has been on the kinematic history of two regionally extensive east-dipping faults, Grejsdalen and Rendalen Faults respectively, which are interpreted as segments of the Fjord Region Detachment Zone. The Grejsdalen fault is clearly an extensional fault placing lower grade Eleonore Bay Supergroup rocks of the hanging wall in tectonic contact with the high grade paragneisses of the Krummedal sequence in the footwall. Evidence for top-to-the-East displacement is not that obvious in the Rendalen Fault where migmatites in the hanging wall are in tectonic contact with the non-migmatite psammitic rocks in the footwall, both units being part of the Krummedal sequence. The appearance of higher grade rocks in the footwall has previously been used to argue that the Rendalen Fault is a top-to-the-W thrust, later reactivated as a top-to-the-E normal fault. A combined structural and petrological study was undertaken to test this hypothesis. The structural results show evidence of top-to-the-northeast extensional movement and no signs of earlier thrusting. The petrological study show P values of c. 12,5-15 kbars and T values of c. 650-700 °C from the footwall and P values of c. 8-9,5 kbars and T values of c. 650-700 °C from the hanging wall.