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Kristin Doering

Kristin Doering

Forskare

Kristin Doering

Stable silicon isotope signatures of marine pore waters – Biogenic opal dissolution versus authigenic clay mineral formation

Författare

  • Claudia Ehlert
  • Kristin Doering
  • Klaus Wallmann
  • Florian Scholz
  • Stefan Sommer
  • Patricia Grasse
  • Sonja Geilert
  • Martin Frank

Summary, in English

Dissolved silicon isotope compositions have been analysed for the first time in pore waters (δ30SiPW) of three short sediment cores from the Peruvian margin upwelling region with distinctly different biogenic opal content in order to investigate silicon isotope fractionation behaviour during early diagenetic turnover of biogenic opal in marine sediments. The δ30SiPW varies between +1.1‰ and +1.9‰ with the highest values occurring in the uppermost part close to the sediment–water interface. These values are of the same order or higher than the δ30Si of the biogenic opal extracted from the same sediments (+0.3‰ to +1.2‰) and of the overlying bottom waters (+1.1‰ to +1.5‰). Together with dissolved silicic acid concentrations well below biogenic opal saturation, our collective observations are consistent with the formation of authigenic alumino-silicates from the dissolving biogenic opal. Using a numerical transport-reaction model we find that approximately 24% of the dissolving biogenic opal is re-precipitated in the sediments in the form of these authigenic phases at a relatively low precipitation rate of 56 μmol Si cm−2 yr−1. The fractionation factor between the precipitates and the pore waters is estimated at −2.0‰. Dissolved and solid cation concentrations further indicate that off Peru, where biogenic opal concentrations in the sediments are high, the availability of reactive terrigenous material is the limiting factor for the formation of authigenic alumino-silicate phases.

Publiceringsår

2016-10-15

Språk

Engelska

Sidor

102-117

Publikation/Tidskrift/Serie

Geochimica et Cosmochimica Acta

Volym

191

Dokumenttyp

Artikel i tidskrift

Förlag

Elsevier

Ämne

  • Oceanography, Hydrology, Water Resources

Nyckelord

  • Authigenic alumino-silicates
  • Biogenic opal
  • Pore water
  • Silicic acid
  • Silicon isotopes

Aktiv

Published

ISBN/ISSN/Övrigt

  • ISSN: 0016-7037