The evolution of Archean continental roots : An integrated study of crustal and mantle xenoliths and intracontinental high-pressure metamorphic belts of Tanzania

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The lower crustal and lithospheric mantle xenolith suites of the Archean Tanzanian craton show lithological variation from kyanite-bearing high-pressure granulite(rare eclogite) to garnet-bearing peridotites. An integrated study of garnet peridotite xenoliths indicates strongly depleted zone in the lithosphere root at depths of~ 130-145 km ; a few samples suggest an initial stabilization at depths of~ 160 km. Moreover, the study revealed that the cratonic root is pervaded by episodic metasomatic melts, which have interacted with lithospheric mantle beneath the Archean Tanzanian craton. This indicates a physicochemical stratification of the lithospheric mantle beneath the Tanzanian craton.