Rare earth elements in foraminifera tests

Abstract

The concentrations of nine rare earth elements (REE) La, Ce, Nd, Sm, Eu, Gd, Dy, Er and Yb, have been determined in mixed species assemblages of foraminifera tests taken from Atlantic Ocean sediment core tops. Reductive cleaning techniques have revealed that REE are present in three phases in foraminifera tests collected from sea floor sediments; REE included in the foraminiferal calcite matrix (termed lattice REE), REE associated with an authigenic FeMn-rich phase adsorbed onto the surface of the test following the death of the organism (termed coating REE) and REE associated with alumino-silicate detritus (termed detrital REE) which commonly infills the test chambers after burial in the sediment. The concentrations of REE in the nondetrital (lattice plus coating) and lattice phases have been measured in this study. Approximately 90% of the REE measured in the non-detrital phase reside in the coating phase, the remainder being present in the lattice phase. These data have been used to investigate the relationship between the distribution of dissolved REE in the ocean and in the coating and lattice phases. In addition to the REE the concentrations of Mn, Fe, Cu, Al and PO 4 have been measured as an aid to characterisation of the various phases.