Spatial and temporal variability in the geochemistry of the sediments at the Main Endeavour Field, Juan de Fuca Ridge

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dc.contributor.authorMills, Melissa
dc.contributor.supervisorCoogan, Laurence
dc.contributor.supervisorCullen, Jay T.
dc.date.accessioned2023-06-01T16:51:30Z
dc.date.available2023-06-01T16:51:30Z
dc.date.copyright2023en_US
dc.date.issued2023-06-01
dc.degree.departmentSchool of Earth and Ocean Sciencesen_US
dc.degree.levelMaster of Science M.Sc.en_US
dc.description.abstractSediments near hydrothermal vents are enriched in metals derived directly from hydrothermal fluids (e.g., Fe, Cu, Zn, Mn) and those associated with scavenging and co-precipitation from seawater with hydrothermally derived Fe-sulfides and Fe-oxyhydroxide minerals (e.g., P, V, Co, Mo, As, REEs). The sediments surrounding active venting have high concentrations of these elements which decrease with distance from the vents due to both hydrothermal plume dilution with seawater and sedimentation of hydrothermal particles. The composition of hydrothermal sediments from the Main Endeavour Field on the Juan de Fuca Ridge, approximately 300 km off the coast of Vancouver Island, was determined using samples collected in sediment traps at three locations along a transect below the hydrothermal plume. These traps were deployed on-axis, 3 km, and 9 km off-axis allowing the spatial variability of the hydrothermal component of the sediments to be assessed. The chemical composition and mass accumulation rates of the hydrothermal component is governed by particle formation in the near vent region and is controlled by particle settling rates with distance from active venting. The concentration and mass accumulation rate of the hydrothermal component of the sediment decreases rapidly with distance, with an order of magnitude decrease between the on-axis and 3 km off axis sediment trap samples, and a further 1-2 orders of magnitude decrease from 3 km off axis to 9 km off axis. Sediment trap samples are also used to create a high-resolution time series of hydrothermal sedimentation over the course of the approximately year sampling period, with each on-axis sample collecting 21 days of sediment and each off-axis sample collecting 12 days of sediment. These samples allowed for an initial assessment of the temporal variation in the chemical composition and mass accumulation rate of the hydrothermal sediment. The variability observed in the hydrothermal component mass accumulation rate suggests that physical oceanographic processes (e.g., flow reversal) impacts the rate of sedimentation. The base of a 50 cm sediment core, collected 2.6 km northwest of the Main Endeavour Field, was dated at ~6,000 years and a high-resolution geochemical reconstruction is used to determine how the hydrothermal component has changed on a 100–1000 year time scale. The comparison of the sediment core to fresh sediment collected by the sediment traps is used to understand how post-depositional changes affect the composition of the hydrothermal component preserved in sediment, as well as the utility of some elements, such as Mn, in reconstructing paleo-hydrothermal sedimentation.en_US
dc.description.scholarlevelGraduateen_US
dc.identifier.urihttp://hdl.handle.net/1828/15156
dc.languageEnglisheng
dc.language.isoenen_US
dc.rightsAvailable to the World Wide Weben_US
dc.subjectJuan de Fuca Ridgeen_US
dc.subjectHydrothermal Ventsen_US
dc.subjectEndeavour Hydrothermal vent fielden_US
dc.subjectMain Endeavour Fielden_US
dc.subjectGeochemistryen_US
dc.subjectMarine Geochemistryen_US
dc.titleSpatial and temporal variability in the geochemistry of the sediments at the Main Endeavour Field, Juan de Fuca Ridgeen_US
dc.typeThesisen_US

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