Geochemistry of deep-sea sediment cores and their relationship with polymetallic nodules from the north- eastern Pacific

Eight sediment cores from the oceanic area close to Clarion Island in the Mexican Economic Exclusive Zone were studied to evaluate their metal content and their relationship to the nodules present in the area. The cores from closer to the East Pacific Rise near 21 degreesN showed high concentrations of organic matter and Zn, and the lowest concentrations of Fe and Mn. The cores from the Mimar Depression, 166 nmiles south-west of Clarion Island, showed the highest concentration of Fe, Mn, Cu, Ni, and Co in sediments and the highest nodule abundance; this may be related to slower bottom currents. Cores 18 and 20 showed significant correlation of Mn with Cu, Ni, and Co, suggesting that these metals are precipitated with the Mn oxides. Core 25 showed a strong correlation of Fe with Mn, indicating different chemical processes. The MnO:Al2O3 ratio was used to evaluate the different sediment sources, and this allowed differentiation of the areas affected by the hydrothermal discharges. Factor analysis of the compositional data produced four major factors diagenetic, hydrothermal, biogenic and detritic-that together account for 74.3% of the sample variance.