a1 Geophysical Observatory, P.O. Box 399, Addis Ababa, Ethiopia.
a2 Dept. of Mineralogy and Petrology, Downing Place, Cambridge.
The succession of individual coloured bands in two manganese ore specimens has been analysed for eight trace elements, and has revealed some long-term chemical variations of possible regional extent throughout the period of ore deposition. Previous work on the distribution of elements between the three types of coloured ore banding is confirmed, and new data on the equivalent coloured bands of the contemporaneous Newfoundland manganese bed reveal an essential chemical, as well as lithological, identity of the two rocks. The effects of weathering and oxidation on ore geochemistry are discussed.