| The millimeter scale compositional variability of Fe-Mn oxide crusts from a seamount near Phoenix Islands in Kiribati, and another near Hawaii was investigated. This study is designed to evaluate how the changes in the mineralogy, internal structure, and chemical composition of crusts relate to their growth history, and elucidate the changes in oceanic water chemistry which the crusts experienced. Thirty-seven major and minor constituents, and the rare earth elements (REE) were analyzed by ICP/AES and ICP/MS in subsamples picked at approximately 2mm intervals throughout the crust sequences. Principal component factor analysis indicates that the chemical composition of crusts in general can be partitioned among four major genetic groups. The geochemistry of the crusts is highly dependent on conditions in the local environment and on the local seawater chemistry rather than on basin-wide oceanic conditions. Paleotracks are proposed for these crust based upon the results of factor scores. These, aided by REE and biostratigraphic data (Cowen et al., 1993), are used to reconstruct the growth history of the crusts and the possible environmental records of ocean. |
