Carbon cycling in the Pliocene Velenje Coal Basin, Slovenia, inferred from stable carbon isotopes

Tjaša Kanduč, Miloš Markič, Simon Zavšek, Jennifer McIntosh

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Stable isotopes of carbon were used to trace organic and inorganic carbon cycles and biogeochemical processes, especially methanogenesis within different geologic substrates of the Pliocene lignite-bearing Velenje Basin in northern Slovenia. Lithotypes of lignite, coalbed gases, calcified woods (xylites), carbonate-rich sediments, and groundwaters were investigated. Carbon isotope (δ 13C) values of the different lignite lithotypes ranged from -28.1 to -23.0%, with the variability likely a function of the original isotopic heterogeneity of the source plant materials and subsequent biogeochemical processes (i.e. gelification, fusinitization, mineralization of organic matter) during the early stage of biomass accumulation and diagenesis. In the lignite seam, CO 2 and CH 4 were the major gas components with small amounts of N 2. The carbon isotope values of CO 213C CO2) and CH 413C CH4) were highly variable, ranging from -9.7 to 0.6% and -70.5 to -34.2%, respectively. Carbon dioxide is likely sourced from a mixture of in situ microbial activity and external CO 2, while CH 4 is dominantly sourced from microbial methanogenesis, with possible addition of thermogenic gas from deeper formations, and the influence of microbial oxidation of methane. Calcified xylites enriched with 13C (δ 13C values up to 16.7%) indicate that microbial methanogenesis was active during formation of the basin. The δ 13C DIC values (from -17.4 to -3.2%) of groundwaters recharging the basin from the Triassic aquifer are consistent with degradation of organic matter and dissolution of dolomite. Groundwaters from the Pliocene sandy and Lithotamnium carbonate aquifers have δ 13C DIC values (from -9.1 to 0.2%) suggestive of degradation of organic matter and enrichment via microbial reduction of CO 2.

Original languageEnglish (US)
Pages (from-to)70-83
Number of pages14
JournalInternational Journal of Coal Geology
Volume89
Issue number1
DOIs
StatePublished - Jan 1 2012

Fingerprint

Lignite
lignite
Isotopes
carbon isotope
methanogenesis
Pliocene
stable isotope
Coal
Biological materials
coal
Groundwater
lithotype
Carbon
carbon
Aquifers
basin
organic matter
groundwater
Carbonates
Recharging (underground waters)

Keywords

  • Carbon cycling
  • Coalbed gas
  • Groundwater
  • Lignite
  • Stable isotopes
  • Velenje Basin

ASJC Scopus subject areas

  • Economic Geology
  • Geology
  • Stratigraphy
  • Fuel Technology

Cite this

Carbon cycling in the Pliocene Velenje Coal Basin, Slovenia, inferred from stable carbon isotopes. / Kanduč, Tjaša; Markič, Miloš; Zavšek, Simon; McIntosh, Jennifer.

In: International Journal of Coal Geology, Vol. 89, No. 1, 01.01.2012, p. 70-83.

Research output: Contribution to journalArticle

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abstract = "Stable isotopes of carbon were used to trace organic and inorganic carbon cycles and biogeochemical processes, especially methanogenesis within different geologic substrates of the Pliocene lignite-bearing Velenje Basin in northern Slovenia. Lithotypes of lignite, coalbed gases, calcified woods (xylites), carbonate-rich sediments, and groundwaters were investigated. Carbon isotope (δ 13C) values of the different lignite lithotypes ranged from -28.1 to -23.0{\%}, with the variability likely a function of the original isotopic heterogeneity of the source plant materials and subsequent biogeochemical processes (i.e. gelification, fusinitization, mineralization of organic matter) during the early stage of biomass accumulation and diagenesis. In the lignite seam, CO 2 and CH 4 were the major gas components with small amounts of N 2. The carbon isotope values of CO 2 (δ 13C CO2) and CH 4 (δ 13C CH4) were highly variable, ranging from -9.7 to 0.6{\%} and -70.5 to -34.2{\%}, respectively. Carbon dioxide is likely sourced from a mixture of in situ microbial activity and external CO 2, while CH 4 is dominantly sourced from microbial methanogenesis, with possible addition of thermogenic gas from deeper formations, and the influence of microbial oxidation of methane. Calcified xylites enriched with 13C (δ 13C values up to 16.7{\%}) indicate that microbial methanogenesis was active during formation of the basin. The δ 13C DIC values (from -17.4 to -3.2{\%}) of groundwaters recharging the basin from the Triassic aquifer are consistent with degradation of organic matter and dissolution of dolomite. Groundwaters from the Pliocene sandy and Lithotamnium carbonate aquifers have δ 13C DIC values (from -9.1 to 0.2{\%}) suggestive of degradation of organic matter and enrichment via microbial reduction of CO 2.",
keywords = "Carbon cycling, Coalbed gas, Groundwater, Lignite, Stable isotopes, Velenje Basin",
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AB - Stable isotopes of carbon were used to trace organic and inorganic carbon cycles and biogeochemical processes, especially methanogenesis within different geologic substrates of the Pliocene lignite-bearing Velenje Basin in northern Slovenia. Lithotypes of lignite, coalbed gases, calcified woods (xylites), carbonate-rich sediments, and groundwaters were investigated. Carbon isotope (δ 13C) values of the different lignite lithotypes ranged from -28.1 to -23.0%, with the variability likely a function of the original isotopic heterogeneity of the source plant materials and subsequent biogeochemical processes (i.e. gelification, fusinitization, mineralization of organic matter) during the early stage of biomass accumulation and diagenesis. In the lignite seam, CO 2 and CH 4 were the major gas components with small amounts of N 2. The carbon isotope values of CO 2 (δ 13C CO2) and CH 4 (δ 13C CH4) were highly variable, ranging from -9.7 to 0.6% and -70.5 to -34.2%, respectively. Carbon dioxide is likely sourced from a mixture of in situ microbial activity and external CO 2, while CH 4 is dominantly sourced from microbial methanogenesis, with possible addition of thermogenic gas from deeper formations, and the influence of microbial oxidation of methane. Calcified xylites enriched with 13C (δ 13C values up to 16.7%) indicate that microbial methanogenesis was active during formation of the basin. The δ 13C DIC values (from -17.4 to -3.2%) of groundwaters recharging the basin from the Triassic aquifer are consistent with degradation of organic matter and dissolution of dolomite. Groundwaters from the Pliocene sandy and Lithotamnium carbonate aquifers have δ 13C DIC values (from -9.1 to 0.2%) suggestive of degradation of organic matter and enrichment via microbial reduction of CO 2.

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