Partition Geochemistry of Sediments From the Romanche Fracture Zone (RFZ), equitorial Atlantic

Abstract

A total of 62 sediment samples from 24 gravity and box cores obtained from an equal number of stations in and around the Romanche Fracture Zone (RFZ) in the Equatorial Atlantic have been subjected to partition chemical analysis in order to investifate the form in which elements studied are present in the sediments and the possible routes by which they become concentrated. The average partition data show that three dominant processes supply elements to the RFZ sediments, namely: biogenic, detrital and hydrogenous deposition. The first is reflected in the acetic acid leach and contributes Ca and Mg. The second is reflected in HCI soluble and residual fractions and contributes AI. Fe, Zn, Cu. Mg. Ti and K. The last is reflected in the acid reducible fraction and contributes Mn, Co. Ni and to a lesser degree Cu and Zn to the sediments. The downcore partition data show that the HC Isoluble fraction of Fe, Mn, Co. Ni, Cu and Zn increase with depth at the expense of the proportion of these elements which are present in the easily reducible ferromanganese phases. This increase also may be explained in terms of diagenetic reactions, which take place within the sediments with depth and by which Fe, Mn, Ni, Cu and Zn are relocated into more resistant fractions.