Origin and Evolution of Precambrian High-Grade Gneiss Terranes, with Special Emphasis on the Limpopo Complex of Southern Africa
High-pressure and ultrahigh-temperature granulite-facies metamorphism of Precambrian high-grade terranes: Case study of the Limpopo Complex
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Published:February 01, 2011
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Toshiaki Tsunogae, Dirk D. van Reenen, 2011. "High-pressure and ultrahigh-temperature granulite-facies metamorphism of Precambrian high-grade terranes: Case study of the Limpopo Complex", Origin and Evolution of Precambrian High-Grade Gneiss Terranes, with Special Emphasis on the Limpopo Complex of Southern Africa, Dirk D. van Reenen, Jan D. Kramers, Stephen McCourt, Leonid L. Perchuk
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We report new petrological data for granulites from the Central Zone of the Limpopo Complex, southern Africa, and construct a prograde P-T path that traverses from high-pressure granulite-facies metamorphism to peak ultrahigh-temperature (UHT) metamorphism by rapid decompression, which was followed by further decompression and cooling. Mg-rich (X Mg ~0.58) staurolite enclosed within poikiloblastic garnet in an Mg-Al-rich rock from the Beit Bridge area is rarely mantled by a sapphirine + quartz corona, suggesting the progress of the prograde dehydration reaction: staurolite + garnet → sapphirine + quartz + H2O. The symplectic sapphirine + quartz developed around staurolite probably implies decompression from P >14 kbar toward the stability of sapphirine + quartz at T ~1000 °C along a clockwise P-T path. The orthopyroxene + sillimanite + quartz assemblage mantled by cordierite aggregates in a pelitic granulite from the same area also suggests extreme metamorphism and subsequent further decompression. Various corona textures such as kyanite + sapphirine, sapphirine + cordierite, and orthopyroxene + cordierite were probably formed as a result of decompression cooling events. The prograde high-pressure metamorphism and the following UHT event relate to the collisional tectonics of the Zimbabwe and Kaapvaal Cratons, which are associated with the amalgamation of microcontinents during the Neoarchean.
- aenigmatite group
- Africa
- Archean
- chain silicates
- cordierite
- decompression
- electron probe data
- facies
- garnet group
- granulite facies
- high pressure
- high-grade metamorphism
- Kaapvaal Craton
- Limpopo Belt
- metamorphism
- mineral assemblages
- mineral composition
- Neoarchean
- nesosilicates
- orthopyroxene
- orthosilicates
- P-T-t paths
- petrography
- Precambrian
- pressure
- prograde metamorphism
- pyroxene group
- ring silicates
- sapphirine
- silicates
- sillimanite
- Southern Africa
- staurolite
- tectonics
- temperature
- terranes
- ultrahigh temperature
- Zimbabwe Craton