Tectono-thermal evolution of Gjelsvikfjella, Western Dronning Maud Land, Antarctica

Doctoral Thesis


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University of Cape Town

East Antarctica is dominated by the East Antarctic Craton, which consists of fragments of Archaean continental crust surrounded by polydeformed orogenic belts (e.g. Maud Belt). The Maud Belt in Dronning Maud Land preserves a high-grade polyphase tectono-thermal history. This belt has traditionally been interpreted as a Mesoproterozoic-age (1.3-0.9 Ga) mobile belt that was later affected by thermal overprint associated with little or no deformation during the Neoproterozoic (0.6-0.5 Ga). Therefore the Maud Belt has been used as a piercing point in Mesoproterozoic supercontinent reconstruction. However, with the growing number of geochronological data pointing to major structural reworking and not just a thermal overprint of the Mesoproterozoic crust during the Pan-African orogeny thereby challenging early models of Mesoproterozoic supercontinent reconstruction. Areas east and west of Gjelsvikfjella record major Pan-African reworking. Thus the outcrops of Gjelsvikfjella provide the linkage between the two areas. Yet, so far little data has been available for this crucial sector. Therefore, detailed fieldwork in the Gjelsvikfjella coupled with petrographic, geochemical and geochronogical data obtained from carefully selected samples reveal a complex tectono-thermal history for this part of the Maud Belt. The SHRIMP U-Pb zircon data obtained make it possible to differentiate between a series of magmatic and metamorphic events. The oldest event recorded is the formation of an extensive, 1140-1130 Ma, volcanic arc. This was followed by 1104 ± 8 Ma granitoids that might represent, together with so far undated mafic dykes part of a decompression melting-related bimodal suite. Only very few relics of late Mesoproterozoic granulite-facies metamorphism is constrained in 1070 Ma strain-protected domains.

Includes bibliographical references (leaves 99-117).