High fO2 Metasomatism During Whiteschist Metamorphism, Zambezi Belt, Northern Zimbabwe |
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| Authors: | JOHNSON S P; OLIVER G J H |
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| Institution: | CRUSTAL GEODYNAMICS GROUP, SCHOOL OF GEOGRAPHY AND GEOSCIENCES, UNIVERSITY OF ST. ANDREWS, ST. ANDREWS KY16 9AL, UK |
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| Abstract: | The Kadunguri Whiteschists are a group of talc- and kyanite-bearinglithologies that occur in the Chewore Inliers from the ZambeziBelt of northern Zimbabwe. They crop out on the southern marginof the Chewore Ophiolite Terrane, a Mesoproterozoic ophioliteand island arc, as a 5 km x 1·5 km, southeasterly dipping,semi-continuous block, and contain the second known naturaloccurrence of yoderite. Major element analyses define the whiteschistswithin the relatively simple MFASH system. Major and trace elementanalyses indicate that the whiteschists originate from the metasomaticalteration of alkalic ocean-island-type metabasalts similarto those in the underlying Ophiolite Terrane. Synmetamorphicor metasomatic mineral parageneses indicate peak P–T conditionsof between 13 and 15 kbar at 550–600°C, and the highlyoxidizing nature of all reactions indicates the presence ofa high fO2 metasomatic fluid. The peak P–T conditionsrequire that this synmetamorphic, exotic metasomatic fluid wasavailable at depths near 55 km. The age of high-pressure metamorphismis constrained within the Pan African tectonothermal cycle at550–520 Ma. Tectonometamorphism in the Zambezi Belt isrelated to a period of extensive crustal thickening possiblyrelated to amalgamation of Gondwanaland. KEY WORDS: Congo Craton; high pressure; Kalahari Craton; metasomatism; whiteschist; Zambezi Belt |
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