Abstract This research paper investigates the thermo-tectonic history of the north Mozambican basement subsequent to the Pan-African metamorphism. Six 40 Ar/ 39 Ar hornblende, three 40 Ar/ 39 Ar biotite and 25 titanite fission-track data place new constraints on the earliest timing of rifting in the central sector of Gondwana, and demonstrate a close linkage between the geometric rift configuration and the ductile metamorphic basement fabrics during the initial dispersal of the supercontinent. The 40 Ar/ 39 Ar hornblende and biotite ages range from c . 542 to 456 Ma and from c . 448 to 428 Ma, respectively. These data record slow basement cooling after the latest Pan-African metamorphism at rates of c . 7–11 °C Ma −1 between Early and Late Ordovician times. Locally, syn- to post-tectonic granitoid emplacements around 500–450 Ma delayed basement cooling to Late Ordovician–Early Silurian times. The titanite fission-track (TFT) ages fall into two age groups of c . 378–327 Ma and c . 284–219 Ma. The older TFT ages record very slow cooling from the Late Ordovician–Early Silurian to below 275±25 °C in the Late Devonian–Early Carboniferous at slow rates of less than 1 °C Ma −1 . This slow cooling is related to decreasing denudation in association with the establishment of pre-Karoo peneplains in central Gondwana. The younger TFT ages record denudation due to rift flank uplift in the context of initial Gondwana disintegration in the Mozambican sector. Corresponding Early–Late Permian crustal extension proceeded obliquely to a NW–SE tensional palaeo-stress field and was associated with a brittle reactivation of easterly trending ductile basement fabrics. In total, up to ≤9–12 km of denudation is deduced from the TFT results since Permo-Carboniferous times.

Abstract Titanite and apatite fission-track ages from Gjelsvikfjella and the eastern Mühlig–Hofmann Mountains, East Antarctica, range between 516±50 and 323±30 Ma and 366±16 and 186±9 Ma, respectively. The thermochronological data set indicates differential cooling of two tectonic blocks (Hochlinfjellet–Festninga and Risemedet). Inverse modelled time–temperature paths suggest that the Hochlinfjellet–Festninga block cooled at first below 60 °C during the mid-Palaeozoic, whereas the Risemedet block cooled during the earliest Triassic. Differential cooling is most probably related to physical separation along active faults, which is associated with Gondwana-wide intracontinental rifting. This tectonic activity shaped the landscape in the study area along structures running perpendicular to the continental margin of Dronning Maud Land. A rift locus was possibly located along the Penck–Jutul graben west of the study area. In contrast to other parts of Dronning Maud Land, Jurassic magmatism and initial break-up between East Africa and East Antarctica did not influence the apatite FT data. Modelled apatite fission-track data indicate the onset of final cooling since the Early Cretaceous, suggesting post-Cretaceous unroofing of the palaeosurfaces in eastern Dronning Maud Land.

Abstract Dronning Maud Land contains a fragment of an Archaean craton covered by sedimentary and magmatic rocks of Mesoproterozoic age, surrounded by a Late Mesoproterozoic metamorphic belt. Tectonothermal events at the end of the Mesoproterozoic and in Late Neoproterozoic–Cambrian times (Pan-African) have been proved within the metamorphic belt. In western Dronning Maud Land a juvenile Mesoproterozoic basement was accreted to the craton at c. 1.1 Ga. Mesoproterozoic rocks were also detected by zircon SHRIMP dating of gneisses in central Dronning Maud Land, followed by a long hiatus for which geochronological data are lacking, an amphibolite to granulite facies metamorphism and syntectonic granitoid emplacement of Pan-African age have been dated. During this orogeny older structures were completely overprinted in a sinistral tranpressive deformation regime, leading to the mainly coast-parallel tectonic structures of the East Antarctic Orogen. Putting Antarctica back in its Gondwana position, the East Antarctic Orogen continues northward in East Africa as the East African Orogen, whereas a connection to the marginal Ross Orogen at the Pacific margin of East Antarctica is suggested along the Shackleton Range. The East Antarctic-East African Orogen resulted from closure of the Mozambique Ocean and collision of West and East Gondwana, i.e. western Dronning Maud Land was part of West Gondwana. During this collision the lithospheric mantle probably delaminated, allowing the asthenosphere to underplate the continental crust and producing heat for the voluminous, typically anhydrous, Pan-African granitoids of central Dronning Maud Land.

Abstract The East African–Antarctica Orogen resulted from the continent–continent collision of East and West Gondwana, or parts thereof, during the Pan-African event at c . 650–510 Ma. The collision overprinted large areas of older, mainly Mesoproterozoic, crust up to granulite facies grade in East Antarctica. The collision history is well documented by folding and thrusting, isothermal decompression and metamorphic zircon growth at c . 580–560 Ma (Pan-African I). The convergence was succeeded by an extensional phase, probably representing orogenic collapse. This Pan-African II event at c . 530–510 Ma is characterized by large-scale extensional structures, finally resulting in the post-tectonic intrusion of voluminous A2-type granitoids. In central Dronning Maud Land the Pan-African II event started with the intrusion of syntectonic igneous rocks within an overall extensional setting. Two new SHRIMP data from gabbro zircons of the Zwiesel Gabbro give ages of 521±5.6 and 527±5.1 Ma. These ages are interpreted as crystallization ages and confirm the interpretation that the gabbro was emplaced early during the Pan-African II event. The gabbro was intruded by a network of leucogranite dykes and veins. Whereas the gabbro appears entirely undeformed, the leucogranite dykes are strongly mylonitized along extensional shear zones, indicating pronounced strain partitioning of the gabbro complex. Within the leucogranite mylonites, large tension gashes developed during mylonitization, indicating very high strain rates. Quartz c-axis orientations from quartz of the tension gashes show a distinct cross-girdle that formed during pure shear deformation. Fluid inclusion data from the leucogranite mylonites and the associated tension gashes mainly reveal recrystallization-related intracrystalline CO 2 -dominant inclusions with relatively low densities of < 1 g cm −3 . The fluid inclusion data are interpreted to represent the last stages of a retrograde P–T path that is characterized by simultaneous cooling and decompression during extensional exhumation, probably succeeding the collapse of overthickened crust. A comparable orogenic collapse of the East African–Antarctic Orogen is reported from other parts of the orogen, such as from western Madagascar and the northern Arabian–Nubian Shield.