Other Scholarly Content

 

The manganese and iron shuttle in a modern euxinic basin and implications for molybdenum cycling at euxinic ocean margins Public Deposited

Downloadable Content

Download PDF
https://ir.library.oregonstate.edu/concern/defaults/jm214t92h

This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Elsevier and can be found at:  http://www.journals.elsevier.com/chemical-geology/.

Descriptions

Attribute NameValues
Creator
Abstract
  • A meaningful application of Mo as a paleo-redox proxy requires an understanding of Mo cycling in modern reducing environments. Stagnant euxinic basins such as the Black Sea are generally regarded as model systems for understanding euxinic systems during early Earth history. However, drawing direct parallels between the Black Sea and open-marine euxinic margins is somewhat complicated by differences in the seawater residence time between these two environments. We report sediment and pore water Mo, U, Mn and Fe data for a euxinic basin with a short seawater residence time; the weakly restricted Gotland Deep in the Baltic Sea. Here, prolonged periods of euxinia alternate with brief inflow events during which well-oxygenated, saline water penetrates into the basin. During these inflow events, dissolved Mn and Fe that has accumulated within the euxinic deep water can be oxidized and precipitated. Co-variations of Mo and U within the sediment suggest that these inflow and oxygenation events may favor Mo accumulation in the sediment through adsorption to freshly oxidized Mn and Fe solid phases. Once Mo is sequestered within the deeper euxinic water and sediments, Mo retention can be further facilitated by conversion to thiomolybdate species and interactions with organic matter and metal sulfides. By comparing our data with those from previous studies where a Mn and Fe “shuttle” for Mo has been demonstrated, we identify two prerequisites for the occurrence of this mechanism. First, there must be a water column oxic-anoxic redox-boundary; this provides a solubility contrast for Mn and Fe. Second, the residence time of seawater in the system has to be short (weeks to a few years). The latter criterion can be met through regular inflow in weakly restricted basins or upwelling in oxygen minimum zones at open-marine continental margins. Based on prior work, we suggest that similar conditions to those currently represented by the Gotland Deep may have prevailed at euxinic ocean margins during the Proterozoic. A boundary between euxinic and oxic water masses overlying the continental shelf may have resulted in accelerated Mo transport through the water column with Mn and Fe (oxyhydr)oxides. We propose that this mechanism, along with Mo isotope fractionation during adsorption, could contribute to the light Mo isotope composition observed in open-marine euxinic sediment facies of the Proterozoic.
Resource Type
DOI
Date Available
Date Issued
Citation
  • Scholz, F., McManus, J., & Sommer, S. (2013). The manganese and iron shuttle in a modern euxinic basin and implications for molybdenum cycling at euxinic ocean margins. Chemical Geology, 355, 56-68. doi:10.1016/j.chemgeo.2013.07.006
Keyword
Rights Statement
Funding Statement (additional comments about funding)
  • Funding was provided by the 7th Framework Program of the European Union (HYPOX project, Grant Agreement No. 226213; Marie Curie IOF to FS, BICYCLE, Grant Agreement No. 300648). US National Science Foundation Grant No. 1029889 supported the participation of JM.
Publisher
Peer Reviewed
Replaces
Additional Information
  • Vol. 355 (2013)
  • description.provenance : Made available in DSpace on 2013-12-05T01:55:39Z (GMT). No. of bitstreams: 1 ScholzFlorianCEOASManganeseIronShuttle.pdf: 2788255 bytes, checksum: cc609b7e3ec28d95d9c3f803db1f89b9 (MD5) Previous issue date: 2013-09
  • Chemical Geology
  • description.provenance : Submitted by Deanne Bruner (deanne.bruner@oregonstate.edu) on 2013-12-05T01:55:39Z No. of bitstreams: 1 ScholzFlorianCEOASManganeseIronShuttle.pdf: 2788255 bytes, checksum: cc609b7e3ec28d95d9c3f803db1f89b9 (MD5)

Relationships

Parents:

This work has no parents.

Items