0000000000515226
AUTHOR
Sönke Brandt
Geochronological evidence for Archaean and Palaeoproterozoic polymetamorphism in the Central Zone of the Limpopo Belt, South Africa
Abstract The Central Zone of Limpopo Belt is a polymetamorphic and complexly deformed Precambrian terrane whose tectonic evolution is still uncertain because details on the timing of its evolution are not well established. We report zircon ages for newly discovered rocks in the Central Zone which document three distinct high-grade tectono-metamorphic events at 3.22, 2.62 and 2.02 Ga. The youngest of these has been well established, but the older two events were so far largely based only on rare zircon overgrowth rims. Most of our samples were collected from a large enclave in the 2.61 Ga Bulai pluton and constitute a strongly deformed, brecciated high-grade assemblage of supracrustal rocks,…
Pressure-temperature evolution during two granulite-facies metamorphic events (2.62 and 2.02 Ga) in rocks from the Central Zone of the Limpopo Belt, South Africa
Abstract The Central Zone of the Limpopo Belt in southern Africa is a classical example of a polymetamorphic terrane that experienced three metamorphic events at 3.22 Ga (M1), 2.66–2.61 Ga (M2) and 2.02 (M3). However, the geodynamic significance of these events is controversial as their P-T evolution was poorly constrained. We present new petrological and geochronological data for the M2 and M3 events. The Neoarchean M2 event is well-preserved in samples from a newly discovered enclave of supracrustal and magmatic rocks in the 2.612 Ga Bulai pluton that shielded the enclave against a Paleoproterozoic M3 overprint, which is dominant in rocks exposed outside the pluton. P-T pseudosection mode…
Comment on “Evolution of high-pressure mafic granulites and pelitic gneisses from NE Madagascar: Tectonic implications”. Tectonophysics, 662, 219–242 (2015) by Ishwar-Kumar et al.
Abstract Determining the possible tectonic regimes active during the Neoproterozoic is crucial for the knowledge of the evolution of the super-continent Gondwana. In Madagascar, that occupies a key position in Gondwana, there is an on-going debate regarding the location of possible suture zones and the implications in terms of paleo-geography. Recognizing high-pressure to ultra-high pressure conditions in mafic rocks is commonly viewed as a strong argument for paleo-subduction zones. Ishwar-Kumar et al. (2015) report unusual high pressure conditions (24 kbar) in Neoproterozoic to Cambrian rocks from North-Central Madagascar (Andriamena Complex). They propose a geodynamic model in which exhu…