The rare earth element geochemistry of hydrothermal sediments from the East Pacific Rise: Examination of a seawater scavenging mechanism

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Abstract

The sediments recovered during DSDP Leg 92 (Site 598) include a complete 16 m.y. record of hydrothermal sedimentation along the western flank of the East Pacific Rise at 19°S. Fifty samples from this sediment column were analyzed to test the hypothesis that the REE composition of the hydrothermal component is primarily acquired via scavenging from seawater. Site 598 provides an ideal sample suite for this purpose: the sediments are lithologically “simple,” primarily consisting of a mixture of hydrothermal materials and biogenous carbonates; the composition of the hydrothermal component is essentially constant through space and time; and the sediments have undergone minimal diagenetic alteration.

The following observations suggest the above-stated hypothesis is true. The Ce anomaly as well as key indices of light and heavy REE behavior all show that the REE pattern of hydrothermal sediments approaches that of seawater with increasing paleodistance from the rise crest. Moreover, shale-normalized REE patterns are similar to that of seawater, varying only in absolute REE content: the REE content increases with distance from the paleo-rise crest and exhibits a pronounced increase in sediments deposited below the paleolysocline. Based on significant correlative relationships between paleodistance from the rise crest and both the concentration and mass accumulation rates (MARs) of REEs and Fe, we conclude the REEs in the hydrothermal component are derived from the interaction of seawater and Fe in the hydrothermal plume.

References (35)

  • T.S Bowers et al.

    Chemical and isotopic mass transfer calculations pertaining to seafloor hydrothermal systems

    Geol. Soc. Amer. Abstract with Programs

    (1933)
  • D.S Cronan

    Underwater Minerals

  • R Dams et al.

    Nondestructive activation analysis of environmental samples

  • H.J.W De Baar

    The marine geochemistry of the rare earth elements

  • H.J.W De Baar et al.

    Rare earth elements in the Pacific and Atlantic oceans

    Geochim. Cosmochim. Acta

    (1985)
  • J Dymond

    The geochemistry of Nazca Plate sediments: An evaluation of hydrothermal, biogenic, detrital and hydrogenous sources

    Geol. Soc. Amer. Mem.

    (1981)
  • J Dymond et al.

    Origin of metalliferous sediments from the Pacific Ocean

    Geol. Soc. Amer. Bull.

    (1973)
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