Portal de Periódicos da CAPES

Trace metal geochemistry in the Cariaco Trench

1987; Pergamon Press; Volume: 34; Issue: 5-6 Linguagem: Inglês

10.1016/0198-0149(87)90048-3

1878-2477

Lucinda Jacobs, Steven Emerson, Sarah S. Huested,

Paleontology and Stratigraphy of Fossils

Profiles of dissolved Mn, Fe, Co, Ni, Cu and Cd were determined in the Cariaco Trench. Solubility trends are consistent with previous metal studies in axoxic fjords and landlocked seas, and serve as a model for the effects of anoxia in an oceanic regime. Class B metals (Cu and Cd) exhibit nearly quantitative removal in the anoxic water column. Transition metal concentrations (Mn, Fe, Co) initially increase across the O2/H2S interface due to the reductive dissolution of metal oxides, and then decrease at depth because of solid phase uptake. Ni profiles show no comparable response to anoxia, but contrast sharply with Ni profiles of the adjacent Venezuelan Basin. Metals which are observed or predicted to be more insoluble in anoxic water (Cu, Cd, Zn, Pb and Mo) can be expected to be enriched relative to detrital input in the underlying sediments. A box model describing this enrichment flux is used to explain the contrasting sediment enrichment patterns observed in the sediments of the Cariaco Trench and Framvaren Fjord, a highly anoxic fjord in Norway. A sediment enrichment hierarchy (Mo > Cd > Cu > Zn > Pb) is derived that predicts which metals should be the most sensitive indicators of open ocean anoxia.