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Discussion of “Extracting K-Ar ages from shales: a theoretical test”

Published online by Cambridge University Press:  09 July 2018

R. F. Ylagan ,
D. R. Pevear  and
P. J . Vrolijk
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Abstract

Illite age analysis (Pevear, 1992) and similar mixing methods demonstrate nearlinear behaviour when corrected for smectite content in illite-smectite and substitutions for K+ in illite layers. Srodon (1999) found that highly curved mixing lines result from theoretical calculations and challenged the validity of IAA. However, our theoretical calculations indicate near-linear mixing lines result when corrected for the amount of smectite and known K+ substitutions (Na+ or NH4+). We conclude that perfect linearity is unattainable because IAA attempts to unmix a system linearly, but the system is based on an exponential function (K-Ar equation). In practice, we believe IAA can successfully determine the age range of illite diagenesis, even though perfect linearity is not attainable because: (1) significant deviations from linearity occur only if >500 Ma separate the diagenetic and detrital ages; (2) IAA analytical uncertainties result in diagenetic and detrital ages that span a range of ages.

Keywords

K-Arshaleillite age analysisillite
Type
Discussion
Information
Clay Minerals , Volume 35 , Issue 3 , June 2000 , pp. 599 - 604
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2000

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References

Pevear, D.R. (1992) Illite age analysis, a new tool for basin thermal history analysis. Pp. 1251 – 1254 in: Proc. 7th Int. Sym. Water-Rock Interactions (Kharaka, Y.K. & Maest, A.S., editors). Park City, Utah.Google Scholar
Pevear, D.R. (1994) Potassium-Argon dating of illite components in an earth sample. United States Patent #5, 288, 695.Google Scholar
Pevear, D.R. (1999) Illite and hydrocarbon exploration. Proc. Natl. Acad. Sci. USA, 96, 3440 – 3446.Google Scholar
Pevear, D.R. & Schuette, C.M. (1993) Inverting the NEWMOD X-ray diffraction forward model for clay minerals using genetic algorithms. Pp. 20 – 41 in: Computer Applications to X-ray Powder Diffraction Analysis of Clay Minerals (Reynolds, R.C., Jr. & Walker, J.R., editors). The Clay Minerals Society, Boulder, Colorado.Google Scholar
Środoń, J. (1999) Extracting K-Ar ages from shales: a theoretical test. Clay Miner. 33, 375 – 378.Google Scholar
Środoń, J., Elsass, F. McHardy, W.J. and Morgan, D.J. (1992) Chemistry of illite-smectite inferred from TEM measurements of fundamental particles. Clay Miner. 27, 137 – 158.Google Scholar