Geochemical Characteristics & Selective Leaching of Transition Elements in Sediments from the Central Pacific Ocean

Abstract

Sediment samples from 4 different areas along the NS transect at 134ᵒW in the central Pacific are subjected to bulk and partition chemical analyses to find the distribution of important transition elements in the mineral phases of sediments. A positive correlation is observed between Fe-Mn-Cu-Ni. Variation in the metal values is observed within a single area also. These changes are related to variation in the dissolution of siliceous and calcareous microorganisms for enrichment of metals and resulting chemical gradients within the sediment column. The geochemical pattern of sediments from different areas indicates a well defined grouping of local variability along the transect. Results of partition patterns show a positive correlation between Mn- Ni-Co in the hydroxylarnineleachable phase (authigenic phase) associated with ferro-manganese oxides indicating a diagenetic enrichment and formation of these authigenic phases. Most of Fe and Cu is associated with the hydrochloric acid soluble fraction indicating the contribution of these elements from iron oxides within the sediments. The leachable elements in the study areas may be separated into 2 major groups one consisting of oxyhydroxides of manganese enriched in Ni and Co, and the other of iron oxides enriched in Cu together with a component associated with carbonate and/or siliceous material where this is present.