Banded iron formation (?) at Grunehogna Craton, East Antarctica – Constraints from aeromagnetic data

Abstract

We report a strong magnetic high over the Giæverryggen at the Grunehogna craton in western Dronning Maud Land, East Antarctica. The anomaly was coarsely mapped by previous surveys. Recently acquired magnetic data (2012/13) better constrain its spatial extent and permit the estimate of a theoretical amplitude value of +4000 to +4200nT at bedrock surface. From the magnetic data, we estimated a minimum magnetic susceptibility in a spherical source body with a midpoint depth of ∼5.6km to be greater than 193×10−3SI, in the absence of relevant remanent magnetization. An exemplary 2.75-D forward modeling is carried out. Comparisons with neighboring magnetic highs in a plate tectonic reconstruction of western Dronning Maud Land and southern Africa reveal clear similarities to the magnetic signature of the Paleoproterozoic banded iron formation in the Mhlapitsi fold and thrust belt near Polokwane (formerly Pietersburg) in South Africa, suggesting a similar source for the Giæver Magnetic Anomaly and allow the interpretation that both regions were juxtaposed in Archaean and Paleoproterozoic times.