Grenville-age versus Pan-African magnetic anomaly imprints in western Dronning Maud Land, East Antarctica

In this article, we examine aeromagnetic data from a part of the western margin of the Pan-African East Antarctic Orogen. The East Antarctic Orogen represents the southern continuation of the East African Orogen that together formed during the collision of East and West Gondwana during late Neoproterozoic/Early Paleozoic times (at ca. 580-515 Ma). The western margin of the East Antarctic Orogen is exposed in Heimefrontfjella, western Dronning Maud Land, where the western front of this orogen crops out as the Heimefront Shear Zone. Crust west of the Heimefront Shear Zone has typical Mesoproterozoic to early Neoproterozoic (Grenville-age) K-Ar and Ar-Ar mineral cooling ages, and magnetic anomalies are broad, of high amplitude, elongate, and craton parallel with long wavelengths. East of the Heimefront Shear Zone, K-Ar and Ar-Ar mineral cooling ages range at between ca. 570 and 470 Ma, and the magnetic anomaly pattern is entirely different. Here, a large magnetic low persists, which is overprinted by small-scale anomalies that are oriented parallel to the regional Pan-African structural trends at a high angle to the Mesoproterozoic anomalies. Thus, the Pan-African tectono-thermal overprint has caused a fundamental redistribution of magnetic minerals. The data show that the combination of aeromagnetic mapping along with detailed fieldwork is a powerful method to delineate the extent of the East Antarctic Orogen in poorly exposed Antarctica.