Influence of Matrix Diffusion and Exchange Reactions on Radiocarbon Ages in Fissured Carbonate Aquifers

The parallel fissure model coupled with the equation of diffusion into the matrix and with exchange reaction equations has been used to derive a simple formula for estimating the influence of matrix porosity and reaction parameters on the determination of radiocarbon ages in fissured carbonate rocks...

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Bibliographic Details
Published in:Water resources research 1991-08, Vol.27 (8), p.1937-1945
Main Authors: Maloszewski, Piotr, Zuber, Andrzej
Format: Article
Language:English
Subjects:
540220 - Environment, Terrestrial- Chemicals Monitoring & Transport- (1990-)
580000 - Geosciences
AGE ESTIMATION
AQUIFERS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CARBON 14
CARBON ISOTOPES
CARBONATE ROCKS
CHEMICAL REACTION KINETICS
DIFFUSION
ENVIRONMENTAL SCIENCES
EVEN-EVEN NUCLEI
FLOW MODELS
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
GEOSCIENCES
GROUND WATER
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPE DATING
ISOTOPES
ISOTOPIC EXCHANGE
KINETICS
LIGHT NUCLEI
MATHEMATICAL MODELS
NUCLEI
ODD-EVEN NUCLEI
OXYGEN COMPOUNDS
POROSITY
RADIOISOTOPES
REACTION KINETICS
ROCK-FLUID INTERACTIONS
ROCKS
SEDIMENTARY ROCKS
SORPTIVE PROPERTIES
SURFACE PROPERTIES
TRACER TECHNIQUES
TRITIUM
WATER
YEARS LIVING RADIOISOTOPES
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Summary:The parallel fissure model coupled with the equation of diffusion into the matrix and with exchange reaction equations has been used to derive a simple formula for estimating the influence of matrix porosity and reaction parameters on the determination of radiocarbon ages in fissured carbonate rocks. Examples of evidently too great radiocarbon ages in carbonate formations, which are not explainable by models for the initial 14C corrections, can easily be explained by this formula. Parameters obtained for a chalk formation from a known multitracer experiment combined with a pumping test suggest a possibility of 14C ages more than three orders of magnitude greater than the ages which would be observed if the radiocarbon transport took place only in the mobile water in the fissures. It is shown that contrary to the solute movement on a small scale and with a variable input, the large‐scale movement, characteristic for the 14C dating, does not necessarily require the knowledge of kinetic parameters, because they may be replaced by the distribution coefficient. Discordant tritium and 14C concentrations are commonly interpreted as a proof of mixing either in the aquifer or at the discharge site. For fissured carbonate formations, however, an alternative explanation is given by the derived model showing a considerable delay of 14C with respect to nonsorbable tracers.
ISSN:0043-1397
1944-7973
DOI:10.1029/91WR01110