Geochemistry of hydrothermal sediments from the Endeavour Segment of the Juan de Fuca mid-ocean ridge




Attar, Armaghan

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Sediment samples were collected during three Ocean Network Canada expeditions to three hydrothermal vent fields at the Endeavour segment of the Juan de Fuca Ridge. The sediments were collected at variable distances (≤ 1340 m) from the vents fields by push core and, in some cases, by suction sampling from base of a chimney structure. The geochemistry of the sediments was investigated in order to understand their formation and the mass fluxes associated with these hydrothermal systems. Qualitative and quantitative approaches have been applied to deconvolve sediments bulk compositions into mass fractions of the different components that they are made up of. Qualitative analysis identified five different end-member components (hydrothermal plume particles, hydrothermal chimney fragments, terrigenous sediment, basalt fragments and organic matter). Using Q-mode factor analysis only three main components are identified. This is due to the geochemical similarity of (i) the hydrothermal plume particles and hydrothermal chimney fragments which are grouped together in this analysis, and (ii) the terrigenous sediment and basalt which are also grouped. Mass fractions of each component were calculated by using a numerical inversion procedure. The samples collected at the base of the chimney are composed of 20-40% plume particles and 56-72% chimney fragments with little contribution from other sediment sources. With increasing distance from the vent fields the contributions of these “hydrothermal” sources to the sediments drop rapidly to <50% within 90 m of the vents and <25% within 120 m from the vents. The mass fraction and chemical composition of the plume particles component, along with the estimates of the chemical flux out of hydrothermal vents and sedimentation rates in the area, are used to make a preliminary estimation of the chemical flux into the ocean.



hydrothermal sediments, Endeavour Segment, geochemistry, factor analysis, total inversion, chemical flux