Be and Be in Submarine Hydrothermal Systems

Abstract

The solution chemistry of the hydrothermal fluids emanating from sediment covered ridges is distinct from that observed on the open ridges where the solutions exit directly from basalt. Differences in composition are believed to result from interaction of a “primary” hydrothermal fluid, similar in composition to that characteristic of sediment-starved open ocean ridge axis, with the overlying sediments.

Because most (>99%) of the cosmic ray produced ¹⁰Be acumulates in sedimentary deposits and because the relative short half-life (1.5xl0⁶ y) of this cosmogenic radioisotope precludes its presence in magmas due to long period recycling, lüBe appears to be an ideal tracer of the postulated reactions between “primary” hydrothermal solutions and the sediments overlying the intrusion zone. Both ⁹Be and ¹⁰Be isotopes have therefore been measured in fluids emanating from sediment-starved hydrothermal systems as well as in hydrothermal solutions and associated sediments from sediment hosted environments. The use of these isotopes to constrain both the chemical composition of the precursor fluid and the magnitude and evolution of the interaction between hydrothermal fluids and overlying sediments, will be discussed.

Extended to hydrothermal systems from back-arc basins, this study allows us to investigate the characteristics of the sedimentary component associated with the subducting oceanic plate.