Geologic evolution of the S?r Rondane Mountains, East Antarctica: Collision tectonics proposed based on metamorphic processes and magnetic anomalies

摘要

The S?r Rondane Mountains of eastern Dronning Maud Land, East Antarctica can be subdivided into two different crustal terranes: the NE-terrane and the SW-terrane. The former is underlain by basement rocks of amphibolite-facies (unit A) and granulite-facies (unit B), and the latter by granulite-facies (unit C) to greenschist-facies (units D and D') rocks. The metamorphic evolution of the NE-terrane exhibits a clockwise pressure-temperature-time (. P-T-t) path and the SW-terrane exhibits a counter-clockwise P-T-t path, and detrital zircon U-Pb ages are also different between the two terranes. The differences in the metamorphic evolution processes and detrital zircon provenance in these two regions can be explained by the collision of the NE-terrane and the SW-terrane which is constrained to have occurred at 600-650. Ma. The collision is interpreted to reflect convergence between the East Maud-East African orogen terrane and the Maud-Nampula terrane of the Kalahari Craton, which are bounded by the Main Tectonic Boundary and passes through the S?r Rondane Mountains. The RTP magnetic anomalies suggest this suture is cut by the subsequent collision boundary between the Kalahari Craton and the Rayner Belt, which is exposed in the Lützow-Holm region. This collisional belt is considered to have formed at approximately 520-580. Ma.