Superimposed Neoarchaean and Paleoproterozoic tectonics in the Terre Adélie Craton (East Antarctica): Evidence from Th–U–Pb ages on monazite and 40Ar/ 39Ar ages

Abstract

In order to understand the tectonic behaviour of a stabilized Neoarchaean continental crust during subsequent tectonic activity, we investigated the composite metamorphic basement along the Terre Adélie and George Vth Land coastline, also known as the Terre Adélie Craton (East Antarctica). Two domains are recognized: (1) a Neoarchaean basement, composed of granulite rocks to the east and overlain to the west by amphibolites, and (2) two Paleoproterozoic detrital basins overly the Neoarchaean crust and extend further west. New geochronological data from the Terre Adélie Craton define a tectonic evolution with three major peaks’ activity. Th–U–Pb electron probe analyses of monazite from the Neoarchaean granulites constrain the main structuration event at ca. 2.45 Ga in agreement with zircon ages from throughout the Neoarchaean domain. Local resetting together with low temperature recrystallization of monazites occurred at ca. 1.7 Ga along hydrated anastomozing metre-scale shear zones. New 40Ar/ 39Ar ages obtained by stepwise heating techniques on amphibole, biotite and muscovite from both the Neoarchaean basement and the Paleoproterozoic basins, illustrate the differential evolutions of basement and its sedimentary cover during the major 1.7 Ga transpressive event. A final event at ca. 1.55–1.50 Ga is only recognized close to the Mertz Shear Zone (145°E) bounding the Terre Adélie Craton to the East. The new data allow us to propose detailed geological pictures of the Terre Adélie Craton geodynamic evolution, from the Neoarchaean to the Mesoproterozoic.