The distribution of rare earth elements in manganese micronodules and sediments from the equatorial and southwest Pacific

Thirty three manganese micronodules and 38 associated sediments from selected areas in the equatorial and southwest Pacific have been analyzed for REE. Significant variations in composition of both micronodules and sediments between the areas are observed. In general, the avarage REE abundance in manganese modules in a given area is higher than that of the associated micronodules but the Ce/La ratio of the micronodules is in some cases higher than that of the nodules. The avarage Ce/La ratio of the micronodules is always higher than that of the associated sediment but the REE abundance is lower in several cases. The Ce anomaly is dominantly positive for micronodules and negative for sediments. Negative Ce anomalies are, however, found in micronodules from the crest of the East Pacific Rise (EPR) where metallogenesis is taking place. Positive Ce anomalies occur in sediments from the Southwestern Pacific Basin between the EPR and New Zealand. The highest Ce/La ratios of both micronodules and sediments are found in this region reflecting the well-oxidized conditions prevailing there.