Secondary ferromanganese microconcretions in Proterozoic sandstones from Norway.

S. Morad

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Ferromanganese microconcretions (nodules, crusts and coatings) were found as reddish dark brown spots in dark grey and black sandstones of the Brottum formation (Upper Proterozoic; the Sparagmite region of southern Norway). The microconcentrations have been precipitated in vugs from percolating ground-water containing Mn2+ and Fe2+ which were leached from biotite and chlorite of the host-rocks. The surface texture of the microconcretions may be smooth (Mn/Fe ratio approx 0.8), reticulated (Mn/Fe ratio approx 2) or made of crystal boxwork (Mn/Fe approx 4). XRD studies indicate the presence of mainly todorokite, birnessite and goethite. (Author's abstract)-E.v.P.

Original languageBritish English
Pages (from-to)529-538
Number of pages10
JournalNeues Jahrbuch fur Mineralogie, Monatshefte
StatePublished - 1985


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