New Data on the Geological Structure and Precambrian Evolution of the Mountain Framework of the Denman Glacier Western Side (East Antarctica): First Paleoarchean Age for Plagiogneisses

The mountain framework of the Denman Glacier is a poorly explored area. However, it is a key region of East Antarctica in the context of studying the Precambrian geological history and geodynamic evolution of the Archean protocratons of the Antarctic Shield and in their comparison with the Archean crust-forming events of other regions of the Earth. Original U–Pb isotope geochronology data from zircons of metamorphic and intrusive rocks sampled from the western side of the Denman Glacier are reported. A geotectonic interpretation of the data was carried out. The Paleoarchean age of crystallization (3355 ± 5.4 Ma) of the magmatic protolith of tonalitic orthogneisses of the Davis granite–gneiss complex was obtained for the first time in this sector of Antarctica. In the Archean time interval, the Davis Paleoarchean protocraton was affected by multistage polymetamorphism in the intervals ~3100–3000 and 2900–2800 Ma ago. A crustal extension associated with the late stage is indicated by syntectonic intrusion of ultramafic dikes and pyroxenite sills (2827 ± 6 Ma). The time when granite veins and subalkaline granitoid plutons formed corresponds to the time of tectono-thermal Pan-African activization in the interval of 550–510 Ma typical for the Rayner Province of East Antarctica. The terrane of Davis craton is similar to the Paleo-Mesoarchean protocratons of East Antarctica, India, and Australia for the time of formation and the evolution of geodynamic processes.