Paleoproterozoic tectonics in the Terre Adélie Craton (East Antarctica)

Abstract

This paper describes the deformation that occurred in the Paleoproterozoic terrains of the Terre Adélie Craton (East Antartica) at ca. 1.69 Ga. The structural pattern is marked by sub-vertical deformation zones, trending N340–360°, that rework sub-horizontal fabrics. Both types of structures developed under similar partial melting conditions (thermal and pressure peaks around 700–750 °C and 500–600 MPa, respectively) and are in part coeval. Vertical zones show kinematic indicators of dextral transpression. Strike-slip components appear to increase in intensity from W to E, toward the contact between Paleoproterozoic terrains and Archaean blocks located to the East. Flat-lying foliations bear stretching lineations, which strike N340–360°, at low-angle to the transpressional shear zones and to the boundaries between major units. Structural and metamorphic signatures are consistent with a model in which hot and weak continental domains converge toward a stiffer craton. Horizontal shortening was accommodated along vertical transpressional zones. Thickening combined with significant magmatic input might have triggered gravity-driven horizontal crustal flow at high angle to the convergence direction.