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Extracting K-Ar ages from shales: the analytical evidence

Published online by Cambridge University Press:  09 July 2018

N. Clauer*
Affiliation:
Centre de Géochimie de la Surface (CNRS-ULP), Ecole et Observatoire des Sciences de la Terre, 67084-Strasbourg France
S. Chaudhuri
Affiliation:
Department of Geology, Kansas State University, Manhattan, KS 66056, USA

Abstract

The relationship between the K-Ar dates of mixed natural clays and the ratios of detrital and diagenetic components follows in most cases a linear trend, which agrees with the theory when the K2O contents of the end-members are similar. However, significant deviations from a linear trend may occur and take the form of poorly-defined concave curves. The absence of a linear trend is less likely to be due to the imprecise determination of the ratio between the two end-members than to heterogeneities of the natural samples which may arise from complex K-Ar evolutions of the detrital and diagenetic end-members. The straight-line approach is of limited use in the definition of diagenetic ages in shales by extrapolating linear trends to diagenetic end-members.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2001

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