Pervasive Pan-African reactivation of the Grenvillian crust and large igneous intrusions in central Dronning Maud Land, East Antarctica

Abstract

Abstract The geological history of central Dronning Maud Land (cDML) is described on the basis of age data, recent observations, and published data. The ages of both the protoliths of the metamorphic rocks of cDML and their primary metamorphism are Grenvillian (1200 to 1000 Ma). Following a long hiatus for which geochronological data are lacking, the Grenvillian crust of cDML was intruded by abundant Pan-African partly charnockitic granitoids and anorthosites of the Dronning Maud Land igneous province. These intrusions occurred predominantly in two Pan-African igneous episodes. The early igneous episode (about 600 Ma), in which the Grubergebirge anorthosite intruded, was followed by Pan-African high-grade metamorphism, intense ductile deformation and then medium-grade retrogression during later Pan-African events (570 to 520 Ma). The Grenvillian structures and metamorphic signature were pervasively overprinted or completely eradicated. The Pan-African metamorphism and tectonism were completed prior to the late Pan-African igneous episode (500 Ma), in which predominantly post-kinematic granitoids, as well as a small anorthosite, intruded. Thus, the present tectonic structure of the crust in cDML was formed during Pan-African events by overprinting of Grenvillian basement and intrusion of granitoids/syenites and anorthosites.