Crustal architecture of the composite East Antarctic craton between the Shackleton Range and Dronning Maud Land

The composite East Antarctic craton is the least understood craton on Earth. It contains cryptic records of 3 Bl years of Earth's history and is a keystone in the Nuna, Rodinia and Gondwana supercontinents. Here we focus on analysing recent aeromagnetic and gravity datasets acquired in a key sector of East Antarctica between the Shackleton Range and Dronning Maud Land. In the Shackleton Range 500 Ma ophiolites, high-P metamorphism, including eclogite facies rocks, and thrust faults suggest the existence of a major suture zone of Pan-African age that separates distinct cratonic blocks, the Coats Land Block and the Mawson Continent. Further north, the ca 1130 to 1040 Ga Maud Belt lies in between the Coats Land Block and the Grunehogna Craton and represents the Antarctic continuation of the Namaqua-Natal Orogen of South Africa. The 650-500 Ma East African-Antarctic Orogen reworked several Precambrian crustal domains in the study region and was responsible for the development of major shear zones.

Aeromagnetic anomaly patterns enable us to trace the extent of Grenvillian-age arc terranes and older Meso to Paleoproterozoic terranes exposed in the Shackleton Range in interior East Antarctica. They also reveal the subglacial extent of widespread rift-related Keweenawan-age (ca 1.1 Ga) igneous rocks exposed in Coats Land and which have been interpreted as related to the Mid-Continent Rift System of Laurentia. Our aeromagnetic and gravity images reveal that the Shackleton Range suture extends at least 500 km into the interior of East Antarctica where it changes orientation from E-W to ca N-S in the Recovery Lakes region. In this area, a major lithospheric boundary also separates thicker crust beneath the Tonian Oceanic Arc Superterrane of eastern Dronning Maud Land from the thinner crust of the Recovery block. Our new interpretation suggests the existence of a complex array of crustal-scale shear/suture zones of inferred Pan-African age that separate a mosaic of weaker and more rigid Precambrian lithospheric provinces in the East Antarctic craton.