Contrasting P-T-t loops from southern East Africa, natal and East Antarctica

Thermobarometric data are compared with the ∼1100 to ∼500 Ma polyphase mobile belts from three separate areas of Africa and Antartica, which originally lay in close proximity within Gondwana. These areas are all characterized by high-grade gneiss terranes formed at ∼1100 Ma (Grenvillian), which were subsequently reworked to a greater or lesser extent at ∼500 Ma (Pan-African). In Zambia, Malawi, Zimbabwe and western Dronning Maud Land peak metamorphic conditions at high temperatures and pressures were attained betwee 1100 and 850 Ma, followed by isothermal decompression (ITD). In Natal and Mozambique, voluminous collision-related granitoid intrusions emplaced between 1200 and 1000 Ma gave rise to high-temperature, moderate pressure metamorphism, with subsequent near-isobaric cooling (IBC). The tectonic setting of these two distinct P-T-t paths can be interpreted as thrust-related uplift in a collisional setting in the case of ITD and as magmatic accretion, subsequent to collisional orogeny, in the case of IBC paths.