First data on the composition and age of subglacial rock from a magnetic anomaly zone (Princess Elizabeth Land, East Antarctica)

During the 69th field season of the Russian Antarctic Expedition in 2023–2024, a joint Russian-Chinese subglacial drilling project was carried out in the northwestern part of the Princess Elisabeth Land. The drilling was meant to decipher the geological nature of a high-amplitude linear magnetic anomaly that runs parallel to the coast for more than 500 km from Princess Elizabeth Land to Mac. Robertson Land, crossing the rift zone of the Lambert Glacier. The nature of this anomaly has remained unknown, while this paper provides the first facts on the age and composition of the bedrock raised from beneath the 541-meter-thick мglacier. The findings show that mafic granulites formed on gabbroids are the source of this anomaly. The protolith of the granulites was formed in an island-arc environment at the turn of 920 million years ago. The rock underwent two stages of metamorphism in the 890–800 Ma period. Estimates of metamorphism parameters indicate stabilization of the region after the collision of Proto-India with Proto-Antarctica and the final assembly of the Rodinia supercontinent.