Distribution of nickel,copper and zinc in the volcanic series of Erta'Ale,Ethiopia

NI, Cu and Zn were measured polarographically in 34 samples of volcanic rocks from the chain of Erta'Ale, Ethiopia. In this chain all rock types from picritic basalts to alkaline and peralkaline rhyolites can be found. The series is marked by a considerable iron enrichment in the intermediate stages. The distribution of Ni, Cu and Zn in the series emphasizes the efficiency of the crystal-field theory in accounting for the behaviour of the elements during magmatic fractionation. Nickel shows a regular variation throughout the trend. The variation of copper is similar to that of iron, but the relative rates of enrichment and depletion show that they are not necessarily associated with the same mineral phases. The behaviour of Zn is rather irregular.