Metal stable isotopes in the marine realm

The field of marine metal stable isotope geochemistry has expanded dramatically since the last edition of the Treatise on Geochemistry. This chapter examines the marine stable isotope cycling of nine transition metals: V, Cr, Fe, Ni, Cu, Zn, Mo, Cd and W. Classifying the metals according to their oceanic residence time and degree of internal cycling enables comparison between systems and, in each case, to draw out the importance of one or more key controlling processes. Isotopic variability internal to the ocean is driven by a range of biogeochemical processes and their interaction with the physical ocean circulation. Mean whole ocean isotopic compositions are controlled by the isotopic composition of oceanic sources and fractionation into sedimentary sinks. The isotopic oceanic mass balance of each metal is reviewed and, in some cases, updated, providing revised estimates of their oceanic residence times.