WHEN WAS THE LIMPOPO OROGENY

The term "Limpopo Orogeny" refers to the common high-grade metamorphic and tectonic event that affected the Archaean rocks of the Central and Southern Marginal Zones of the Limpopo Belt and its influence on the adjacent portions of the Kaapvaal Craton. Available geochronological data from muscovite-kyanite prograde metamorphic assemblages, zircon in igneous charnoenderbite and enderbite, muscovite in syntectonic pegmatite bodies formed in shear zones, partial melts and syn- and post-tectonic plutons of granodiorite and granite indicate that this orogeny occurred during the time interval from approximately 2700 Ma ago to approximately 2650 Ma ago. The retrograde phase of this orogeny, from the onset of the response phase (M2) until the rocks were subjected to rehydration (M3), was very rapid, probably lasting approximately 7 Ma from approximately 2671 Ma to approximately 2664 Ma ago. Similar but limited data from the Northern Marginal Zone and adjacent portions of the Zimbabwe Craton suggest that rocks there were subjected to a more recent interval of high-grade metamorphism and tectonism, extending from approximately 2600 Ma until approximately 2550 Ma.