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Diagenetic chlorite formation in some Mesozoic shales from the Sleipner area of the North Sea

Published online by Cambridge University Press:  09 July 2018

A. Hurst*
Affiliation:
Statoil, Forus, Postboks 300, N-4001 Stavanger, Norway

Abstract

Diagenetic chlorite is forming as a result of temperature-controlled burial diagenesis in shales from the Sleipner area of the North Sea. Accompanying chlorite diagenesis, kaolinite and illite-smectite decrease in abundance, and illite increases in abundance. These clay mineral transformations occur between 122–126°C at temperatures higher than normally expected for chlorite diagenesis. Kaolinite and ordered illite-smectite are largely unaffected by diagenesis below 100°C. It is proposed that chlorite diagenesis is thus delayed due to the absence of a source of ions resulting from smectite decomposition. Clay mineralogy is of no lithostratigraphic use in the Jurassic sediments of the Sleipner area. However, the zone of chlorite diagenesis is a reliable indicator of maximum burial temperature.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1985

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