New detailed aeromagnetic and geological data of eastern Dronning Maud Land: Implications for refining the tectonic and structural framework of S?r Rondane, East Antarctica

摘要

The S?r Rondane Mountains (SRM) in eastern Dronning Maud Land (DML) are located in an area, where two apparent Pan-African (650–520 Ma) orogenic mobile belts appear to intersect, the East African-Antarctic Orogen and the Kuunga Orogen. Hence, a better understanding of the tectonic structure of the S?r Rondane region is an important key for unravelling the complex geodynamic evolution of the eastern DML and adjacent regions of East Antarctica during the Late Neoproterozoic/Early Palaeozoic amalgamation of Gondwana. The SRM were recently (2011–2012) aerogeophysically investigated with a5kmflightlinespacing,coveringatotalareaof～140,000km~2. The aeromagnetic data are correlated with ground-based magnetic susceptibility measurements and geological field data and allow to project tectonic terranes and individual structures into ice-covered areas. Magnetic anomalies and basement foliation trends are collinear in areas dominated by simple shear deformation, whereas an area of largescale refolding correlates with a subdued small-scale broken magnetic anomaly pattern. The latter area can be regarded as a distinct tectonic domain, the central S?r Rondane corridor. It magnetically separates the SRM into an eastern, a central, and a western portion. This subdivision is presumably related to late Pan-African extensional tectonics and suggests that such a tectonic regime may play a larger role than previously assumed. Voluminous late Pan-African granitoids, which are mainly undeformed, correlate with positive magnetic anomalies between +30 and +80 nT, while a strong magnetic high (+680 nT) near the granitic intrusion at Dufekfjellet is caused by a highly magnetised enigmatic body. The recently discovered prominent magnetic anomaly province of southeastern DML continues into the southern part of the S?r Rondane region, where only a few outcrops are exposed. Findings at these westernmost nunataks of the SRM indicate that the subdued magnetic anomaly pattern of this southeastern DML province is most likely caused by the predominance of metasedimentary rocks of yet unknown age.