Stable isotope ratios and the evolution of acidulous ground water

Martin Dietzel*, Thorsten Kirschhoff

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

Ground waters in North Hesse (Germany) are conspicuous by high amounts of dissolved inorganic carbon (DIC) at low pH. The DIC is received from the uptake of soil CO2 and CO2 of volcanic origin and the subsequent dissolution of Triassic and Permian limestone and dolomites. The volcanic CO2 is related to Miocene basaltic magma which has liberated gaseous CO2 during the breakthrough to Triassic and Permian sediments. The volcanic CO2 (-6 < δ13 CCO2 < -3‰, PDB) was trapped within pore spaces and intra- and intergranulares of Permian evaporites and Triassic sandstones and was stored within such reservoirs until recent times. The uptake of volcanic CO2 occurs as ground water migrates through such reservoirs. The 13C/12C-signatures of the DIC indicate mixture of soil-CO2 and CO2 of volcanic origin for the dissolution of marine limestone and dolomites. The obtained two types for CO2 of volcanic origin with δ13CCO2-values of - 10 ± 3 and +2 ± 2‰ can be explained by diffusion of CO2 through micropores, faults, and interfaces of solids. This mobilisation of CO2 is accompanied with a kinetic fractionation of ≈ -9‰. 13C-depleted CO2 is liberated from the reservoir, whereas 13CO2 is accumulated in the residue.

Original languageEnglish
Pages (from-to)229-254
Number of pages26
JournalAquatic Geochemistry
Volume8
Issue number4
DOIs
Publication statusPublished - 2002

Keywords

  • Acidulous ground water
  • Calcite
  • Carbonic acid
  • Dolomite
  • Isotope fractionation
  • Stable isotopes
  • Volcanic CO

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics

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