Manganese mineralisation in the Mesoproterozoic Palapye Group of East-Central Botswana occurs as a thin, but laterally extensive Mn-rich bed hosted by a succession of very weakly metamorphosed sandstone and shale. The manganese minealisation is stratiform and of very shallow marine or fluvial origin. The mineralised sandstone is characterised by the occurrence of cm-sized carbonate oncoids and rip-up slasts. The manganiferous bed is affected by a distinct hydrothermal overprint. In the vicinity of large regional faults the average thickness of the manganiferous bed increases strongly as a result of hydrothermal alteration and the primary mineralogy is transformed to a complex assemblage of Mn silicates and Mn-carbonates, accompanied by considerable amounts of barite and other minerals of typically hydrothermal origin. Supergene alteration leads to the replacement of Mn carbonates and silicates by poorly crystalline Mn-oxihydroxides. The primary mineralogy of the manganese mineralsation remains unknown as the only unweathered sample material available for study was strongly hydrothermally altered.
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