Synopsis
Highly crystalline manganiferous blocks consisting mainly of manganite and pyrolusite occur in a supraglacial flow till. Field evidence indicates that mineralization, which is of high chemical purity and notably free of iron, occurred
in situ.
The segregation of manganese from iron probably occurred as a result of selective dissolution of manganese in waterlogged organic-rich soil or sediment. Manganese and associated barium may have been transported by groundwater to its present location largely in the form of colloidal hydrous manganese dioxide. Initial deposition appears to have been localized by impersistent clay bands, with further deposition being catalysed by previously deposited manganese oxides. Local topography and depth of the clay bands relative to a fluctuating water table were probably critical in localizing the mineralization.
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