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Kibaran magmatism and Pan-African granulite metamorphism in northern Mozambique: Single zircon ages and regional implications

Abstract:

Single zircons from granitoid orthogneisses in the foreland of the Lurio Belt of northern Mozambique were dated by the evaporation method and yielded 207Pb/206Pb magmatic emplacement ages between 1040.1±0.4 and 1148.2±0.4 Ma. These data confirm previous Rb-Sr whole rock and SHRIMP zircon analyses and record a period of magmatic activity corresponding to the Kibaran event of east central Africa. A ∼1300 Ma old zircon xenocryst in one sample suggests the presence of still older crust in the region. Metamorphic zircons from a granulite-facies psammopelitic gneiss of the Mugeba klippe, which is derived tectonically from the Lurio Belt, were dated by evaporation, conventional techniques and SHRIMP at ∼615 Ma. This is interpreted as reflecting the peak of high-grade metamorphism in this rock and, by implication, in the Lurio Belt. It is concluded from this that the main metamorphism in the basement of northern Mozambique occured in Pan-African times, as is the case in adjacent regions of Tanzania and Malawi, and that this may be the result of collision between East and West Gondwana. © 1997 Elsevier Science Limited.