Single-zircon geochronology and Nd isotopic systematics of Proterozoic high-grade rocks from the Mozambique belt of southern Tanzania (Masasi area): implications for Gondwana assembly
The Mozambique belt of southern Tanzania is underlain by locally restricted 1100–950 Ma (late Kibaran) granitoid gneisses that were derived from remelting of Archaean continental crust, as suggested by Nd isotopic systematics. These rocks were deformed and metamorphosed during an intense Neoproterozoic (Pan-African) event at around 630 Ma together with tectonically interlayered and widespread 800–650 Ma granitoid gneisses and minor clastic metasediments. The 800–650 Ma granitoids were derived predominantly from Neoproterozoic juvenile melts. There is no evidence for pre-800 Ma deformation. The 630 Ma event led to extensive migmatization in all gneisses and caused local melting. Similarities in age and tectonometamorphic evolution between these rocks and similar gneisses in northern Mozambique and southern Malawi suggest a similar geological evolution. However, distinctly different ages for the peak of metamorphism in Tanzania, Malawi and Mozambique indicate diachronous high-grade events that may be associated with terrane accretion and continental collision during orogenesis and favour the view that East Gondwana was not a coherent block during formation of the Gondwana supercontinent.