Geodynamic evolution of eastern Dronning Maud Land based on research highlights from an international geological-geophysical approach

Wilfried.Jokat [ at ]


East Antarctica formed by amalgamation of a number of cratons along distinct Ediacaran mobile belts. They include the ca. 600-500 Ma old East African-Antarctic Orogen (EAAO) and the Kuunga Orogen, which seem to converge in the region of Dronning Maud Land. In central Dronning Maud Land, the major Forster Magnetic Anomaly separates rocks with Grenville-age protolith ages (ca. 1130-1000 Ma) to the West from rocks with Early Neoproterozic protolith ages (ca. 1000-930 Ma) to the East. The Forster Magnetic Anomaly is therefore interpreted as a suture between these two provinces. New field work during three recent international expeditions, Geodynamic Evolution of East Antarctica (GEA) I to III, and first geoscientific results reveal a complex tectonic architecture between central Dronning Maud Land and Sør Rondane in eastern Dronning Maud Land. East of the Forster Magnetic Anomaly, the magnetic anomaly pattern changes significantly and typical Maud-type crust is apparently lacking. Particularly, the GEA II campaign targeted a range of previously unvisited nunataks between Sør Rondane and central Dronning Maud Land (from Blåklettane and Bergekongen in the East to Urna and Sørsteinen in the West). These nunataks are dominated by medium- to high-grade metasedimentary and metavolcanic rocks of possibly Neoproterozoic age, including abundant marble and graphite schists. Sør Rondane in eastern Dronning Maud Land, on the other hand, is dominated by two distinct blocks separated by the dextral Main Shear Zone. The northwestern block appears as part of the EAAO or the Kuunga Orogen, where new SHRIMP zircon data from metamorphic rims provide ages of ca. 560 Ma. The southeastern block is made up of a TTG terrane, which provides 12 new zircon crystallization ages ranging from 1000-930 Ma. The TTG terrane has predominantly oceanic affinities and the wide range of ages might indicate long-lasting accretionary tectonics. The TTG terrane shows in part limited tectonic overprint and could be the southeastern foreland of the EAAO or the Kuunga Orogen. Close to the contact of the two blocks, grey gneisses and augen-gneisses gave zircon crystallization ages of ca. 750 Ma. Such ages were previously unknown from the EAAO. The Forster Magnetic Anomaly therefore separates distinctly different parts of the EAAO. These are (i) a reworked, mainly Grenville-age crust to the West representing the overprinted margin of the Kalahari Craton, and (ii) a part of the orogen dominated by Neoproterozoic accretionary tectonics to the East. This difference is also reflected in the geochemistry of voluminous late-tectonics granitoids across the whole belt.

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Conference (Talk)
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GeoFrankfurt 2014, 21 Sep 2014 - 24 Sep 2014, Frankfurt.
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Läufer, A. , Jacobs, J. , Elburg, M. , Clark, C. , Kleinhanns, I. , Andersen, T. , Mieth, M. , Ruppel, A. , Estrada, S. , Damaske, D. , Lucka, N. , Lisker, F. and Jokat, W. (2014): Geodynamic evolution of eastern Dronning Maud Land based on research highlights from an international geological-geophysical approach , GeoFrankfurt 2014, Frankfurt, 21 September 2014 - 24 September 2014 .

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