Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Atmospheric weathering of Scandinavian alum shales and the fractionation of C, N and S isotopes
Stockholm University, Faculty of Science, Department of Geological Sciences.
Stockholm University, Faculty of Science, Department of Geological Sciences.
Stockholm University, Faculty of Science, Department of Geological Sciences.
Stockholm University, Faculty of Science, Department of Geological Sciences.
Show others and affiliations
Number of Authors: 7
2016 (English)In: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 74, 94-108 p.Article in journal (Refereed) Published
Abstract [en]

Subaerial exposure and oxidation of organic carbon (C-org)-rich rocks is believed to be a key mechanism for the recycling of buried C and S back to Earth's surface. Importantly, processes coupled to microbial C-org oxidation are expected to shift new biomass delta C-13(org) composition towards more negative values relative to source. However, there is scarcity of information directly relating rock chemistry to oxidative weathering and shifting delta C-13(org) at the rock-atmosphere interface. This is particularly pertinent to the sulfidic, C-org-rich alum shale units of the Baltoscandian Basin believed to constitute a strong source of metal contaminants to the natural environment, following subaerial exposure and weathering. Consistent with independent support, we show that atmospheric oxidation of the sulfidic, C-org-rich alum shale sequence of the Cambrian-Devonian Baltoscandian Basin induces intense acid rock drainage at the expense of progressive oxidation of Fe sulfides. Sulfide oxidation takes priority over microbial organic matter decomposition, enabling quantitative massive erosion of C-org without producing a delta C-13 shift between acid rock drainage precipitates and shale. Moreover, C-13 enrichment in inorganic carbon of precipitates does not support microbial C-org oxidation as the predominant mechanism of rock weathering upon exposure. Instead, a Delta S-34 = delta S-34(shale) - delta S-34(precipitates) approximate to 0, accompanied by elevated S levels and the ubiquitous deposition of acid rock drainage sulfate minerals in deposited efflorescent precipitates relative to shales, provide strong evidence for quantitative mass oxidation of shale sulfide minerals as the source of acidity for chemical weathering. Slight delta N-15 depletion in the new surface precipitates relative to shale, coincides with dramatic loss of N from shales. Collectively, the results point to pyrite oxidation as a major driver of alum black shale weathering at the rock-atmosphere interface, indicating that quantitative mass release of C-org, N, S, and key metals to the environment is a response to intense sulfide oxidation. Consequently, large-scale acidic weathering of the sulfide-rich alum shale units is suggested to influence the fate and redistribution of the isotopes of C, N, and S from shale to the immediate environment.

Place, publisher, year, edition, pages
2016. Vol. 74, 94-108 p.
Keyword [en]
Ancient organic carbon, Black shales, Carbon, Nitrogen, and Sulfur isotopes, Weathering, Sulfide oxidation, Organic matter oxidation
National Category
Earth and Related Environmental Sciences
Identifiers
URN: urn:nbn:se:su:diva-137751DOI: 10.1016/j.apgeochem.2016.09.006ISI: 000388499400009OAI: oai:DiVA.org:su-137751DiVA: diva2:1064292
Available from: 2017-01-12 Created: 2017-01-10 Last updated: 2017-01-12Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Chi Fru, ErnestHemmingsson, ChristofferCallac, NolwennPérez, NathalieBroman, Curt
By organisation
Department of Geological Sciences
In the same journal
Applied Geochemistry
Earth and Related Environmental Sciences

Search outside of DiVA

GoogleGoogle Scholar

Altmetric score

Total: 4 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf