Petrogenesis of metemorphosed manganese deposits and the nature of the precursor sediments

This paper reviews the current concepts on petrogenesis of metamorphosed manganese-rich sedimentary rocks with the aim to identify the processes, their various controls and the possible progenitors. On the basis of mineralogical composition, five distinct rock types have been identified which show 21 mineral assemblages in total. Mineralogical, textural and chemical data on naturally occurring phases of these five rock types are also presented. These data, together with the results of experimental studies are used to interpret the metamorphic evolution of the different rock types. Finally, an attempt has been made to determine the possible precursor sediment types