Samples of ferromanganese nodules and encrustations embedded in Ammonitico Rosso from two supposed seamounts and one supposed basin setting in the Bakony mountains, have been examined texturally, mineralogically and chemically in order to compare them with modern marine manganese nodules and crusts as an aid in their palaeoenvironmental reconstruction. The deposits are richer in CaCO3 than modern ferromanganese oxide deposits, reflecting their microscopically observed intimate association with foraminiferal remains. Mineralogically they consist mainly of calcite and goethite with subordinate todorokite, and some pyrolusite in cores consisting of Mn-impregnated interclasts. Post-depositional diagenetic changes appear to have been minimal. Chemically the deposits exhibit highly variable Mn/Fe ratios, are low in Cu and intermediate in Ni, Co and Zn compared with modern oceanic ferromanganese oxides. Overall, they are similar to modern deposits from marginal seamounts and banks, in keeping with their postulated continental margin origin, but their chemical composition does not facilitate a division into seamount and basin varieties.-J.M.H.
|Number of pages||14|
|Journal||Chemie der Erde - Geochemistry|
|Publication status||Published - Jan 1 1986|
ASJC Scopus subject areas
- Geochemistry and Petrology