K-Ar dating by smectite extracted from bentonite formations

Nakata, Eiji; Yukawa, Mei; Okumura, Hiroshi; Hamada, Masaaki

doi:10.1051/e3sconf/20199812015

Cited by 1 publication

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“…However, the obtained age is then to be attributed to the nucleation of the illite layers and not to that of the K-empty smectite host. Of some importance in the correlation between crystal identification and age, any misapplied crystallographic interpretation can raise inappropriate conclusions (e.g., [73]). Since pure smectite does not contain any K and Rb, its crystallization cannot be dated by either the K-Ar or the Rb-Sr methods.…”

Section: Which Dating Benefits Can Results From Downsizing Clay Minerals?mentioning

confidence: 99%

How Can Technical Aspects Help Improving K-Ar Isotopic Data of Illite-Rich Clay Materials into Meaningful Ages? The Case of the Dominique Peter Uranium Deposit (Saskatchewan, Canada)

Clauer¹

2020

Geosciences

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Previously published K-Ar dating results of <2 μm illite separates from uranium-hosting and associated barren rocks from Dominique Peter district of the Carswell circular structure in the Athabasca Basin (Canada) were considered to trace four distinct tectonic-thermal events at 1447 ± 45, 1282 ± 40 and 1184 ± 15 (all errors at ± 2 Ma, with a younger, less constrained episode at ~900 Ma. Recent analyses of K-Ar ages of additional <0.2 μm illite fractions from a few initial samples demonstrate that the intermediate ages at ~1280 and ~1185 Ma result, in fact, from mixing of two generations of illite that precipitated at ~1450 and ~900 Ma. They have, therefore, no stratigraphic value, while the two tectonic-thermal episodes at 1448 ± 48 and 937 ± 39 Ma appear to be historically sound. In fact, the analytical procedure of isotopic dating clay materials is of more importance than is often stated. For instance, a safe way to evaluate and constrain best numerical isotopic data of clay separates into ages is combining data of two size splits from several samples. If such age data, especially from size fractions of indurated host rocks, are scattered and point towards the higher data of the coarser fractions, they are potentially enriched in earlier crystallized K-rich components, and should consequently be discarded. The occurrence of detrital or early-crystallized components in clay-rich separates becomes a serious concern when comparing ages generated by various isotopic methods on mineral separates of various whole rocks. It is especially verified in very old, metal-rich deposits such as the uranium-rich deposits of the Saskatchewan Basin. These deposits and their host rocks were studied extensively by a large spectrum of isotopic methods on many types of rocks in a widely dispersed area, and for which the numerical statistics became, sometimes, more central in the interpretation than the specificity of the successive events in the host rocks.

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Section: Which Dating Benefits Can Results From Downsizing Clay Minerals?mentioning

confidence: 99%

How Can Technical Aspects Help Improving K-Ar Isotopic Data of Illite-Rich Clay Materials into Meaningful Ages? The Case of the Dominique Peter Uranium Deposit (Saskatchewan, Canada)

Clauer¹

2020

Geosciences

View full text Add to dashboard Cite

show abstract

K-Ar dating by smectite extracted from bentonite formations

Cited by 1 publication

References 9 publications

How Can Technical Aspects Help Improving K-Ar Isotopic Data of Illite-Rich Clay Materials into Meaningful Ages? The Case of the Dominique Peter Uranium Deposit (Saskatchewan, Canada)

How Can Technical Aspects Help Improving K-Ar Isotopic Data of Illite-Rich Clay Materials into Meaningful Ages? The Case of the Dominique Peter Uranium Deposit (Saskatchewan, Canada)

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