Geochemistry of supergene manganese oxide deposits, Groote Eylandt, Australia

Some 20 different supergene Mn oxide ores and associated secondary rocks from the Groote Eylandt manganese deposit were analyzed for their major, minor, and trace element content. It is possible to correlate groups of trace elements to individual minerals using a quantitative normalization technique that determines the mineralogical composition of the samples. Members of these groups tend to be elements with specific ionic radii, contained in the following host phases: pyrolusite (~0.4 Å and ≥1 Å), cryptomelane and todorokite (~0.7 Å), romanechite (no signficant correlation detected), kaolinite (~0.6, 0.8 and 1.0 Å), and goethite (~0.4 Å). Generally, distinctive supergene horizons, enriched in certain elements (eg Zn, Sr) and minerals, develop within the stratigraphic section. -from Authors