Hydrothermal scavenging on the Juan de Fuca Ridge: {sup 230}Th{sub xs}, {sup 10}Be, and REEs in ridge-flank sediments

Journal Article · Wed Oct 01 04:00:00 EDT 1997 · Geochimica et Cosmochimica Acta

DOI:https://doi.org/10.1016/S0016-7037(97)00230-5· OSTI ID:617821

German, C R; Colley, S; Higgs, N C; Ludford, E M ^[1]

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1. Southampton Oceanography Centre, Southampton (United Kingdom); and others

We have investigated the geochemistry of a hydrothermally enriched sediment core recovered from the western flank of the N.Cleft Segment, Juan de Fuca Ridge, {approximately}8km west of the {open_quotes}MegaPlume{close_quotes} area previously identified near 45{degrees}N. The core contains varying biogenic, lithogenic, and hydrothermal components, as reflected in CaCO{sub 3}, Al, and Fe contents, respectively. Horizons of pronounced hydrothermal input, in core-top sediments and at depth, exhibit increased concentrations of Fe, Cu, Zn, and Pb and shifts in Pb isotopic compositions toward nonradiogenic (MORB/hydrothermal) values. REE concentrations co-vary with hydrothermal Fe down-core, and shale-normalised REE distribution patterns exhibit both negative Ce-anomalies and positive Eu-anomalies, indicative of input from plume-particle fall-out. Unsupported {sup 230}Th{sub xs} activities down-core are consistent with continuous slow sediment accumulation rates of 0.54 cm/ky for 200 ky since the deposition of the deeper Fe-rich horizon. {sup 10}Be{sub (0)}, and {sup 9}Be isotope concentrations also co-vary with hydrothermal Fe down-core and exhibit {sup 10}Be{sub (0)} ratios which approach that of Pacific Ocean deep water, indicative of a seawater-scavenging source. 49 refs., 9 figs., 7 tabs.

• OSTI ID: 617821
• Journal Information: Geochimica et Cosmochimica Acta, Journal Name: Geochimica et Cosmochimica Acta Journal Issue: 19 Vol. 61; ISSN GCACAK; ISSN 0016-7037
• Country of Publication: United States
• Language: English

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