Depositional behaviors of trace metals around hydrothermal vents in the Scotia Sea

Abstract

Sediment deposition along the East Scotia Ridge (ESR) in the Southern Oceanis dominated by biogenic sediment due to its location within the diatom belt and is influenced by the Antarctic Circumpolar Current mainly flowing west to east. Hydrothermal vent systems occur along the ESR, are characterized by nine tectonic segments (E1-E9). Sediment cores in the vicinity of ridge segments E2 and E9 from the ESR were analyzed to gain a better understanding of potential vent fluids related to trace metal distributions in surrounding modern marine sediments. Solid phase multicore and porewater samples collected during the R/V Polarstern Expedition PS_119 were located on both east and west sides of the ESR. Samples were selected at different distances from the hydrothermal vents along two west to east transects crossing E2 and E9 to gain a broader understanding of how chemical signatures within the sediment column change due to their proximity to the vents. As hydrothermally emitted plumes move throughout the water column, they affect where trace metals are deposited onto underlying sediments. Each core was analyzed using an inductively coupled plasma mass spectrometry. Analysis across the transects show a steady increase in trace metal concentrations on the eastern side of the ESR compared to samples from the western side indicating a currents-induced eastward movement of hydrothermal plumes from the ESR. In addition, sediments near E9 exhibited much higher trace metal enrichments compared to segment E2 signifying a more trace metal-rich magmatic substrate source and different water-rock interactions increased metal concentrations within plumes and their deposits. Understanding the effects of hydrothermal activity on marine sediment is crucial when studying the productivity of an area using trace metal proxies because trace metal input from hydrothermal vents can overprint chemical signatures left from phytoplankton in marine sediments. Silver seems to be relatively unaffected by hydrothermal activity as it has similar concentrations within the cores analyzed, while cobalt and copper concentrations fluctuated with different distances from the hydrothermal vents. Thus, copper and cobalt have the potential to indicate changes in deep ocean currents, while silver may be a good productivity proxy in the Southern Ocean.