P–T–fluid evolution in the Mahalapye Complex, Limpopo high-grade terrane, eastern Botswana |
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| Authors: | K HISADA L L PERCHUK T V GERYA D D VAN REENEN B K PAYA |
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| Institution: | Institute of Experimental Mineralogy, Russian Academy of Sciences, Chernogolovka, Moscow District, 142432 Russia (); Department of Petrology, Geological Faculty, Moscow State University, Moscow, 119899, Russia (); Department of Geology, Rand Afrikaans University, PO Box 524, Auckland Park 2006, Johannesburg, South Africa; Geological Survey of Botswana, Private Bag 14, Lobatse, Botswana |
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| Abstract: | Metapelites, migmatites and granites from the c. 2 Ga Mahalapye Complex have been studied for determining the P–T–fluid influence on mineral assemblages and local equilibrium compositions in the rocks from the extreme southwestern part of the Central Zone of the Limpopo high‐grade terrane in Botswana. It was found that fluid infiltration played a leading role in the formation of the rocks. This conclusion is based on both well‐developed textures inferred to record metasomatic reactions, such as Bt ? And + Qtz + (K2O) and Bt ± Qtz ? Sil + Kfs + Ms ± Pl, and zonation of Ms | Bt + Qtz | And + Qtz and Grt | Crd | Pl | Kfs + Qtz reflecting a perfect mobility (Korzhinskii terminology) of some chemical components. The conclusion is also supported by the results of a fluid inclusion study. CO2 and H2O ( = 0.6) are the major components of the fluid. The fluid has been trapped synchronously along the retrograde P–T path. The P–T path was derived using mineral thermobarometry and a combination of mineral thermometry and fluid inclusion density data. The Mahalapye Complex experienced low‐pressure granulite facies metamorphism with a retrograde evolution from 770 °C and 5.5 kbar to 560 °C and 2 kbar, presumably at c. 2 Ga. |
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| Keywords: | fluid inclusions fluid infiltration granulite-facies Limpopo high-grade terrane metasomatism migmatization |
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