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Illitization and organic maturity in Silurian sediments from the Southern Uplands of Scotland

Published online by Cambridge University Press:  09 July 2018

R. B. Pearce
Affiliation:
Department of Geology, University of Southampton, Southampton SO9 5NH, UK
T. Clayton
Affiliation:
Department of Geology, University of Southampton, Southampton SO9 5NH, UK
A. E. S. Kemp
Affiliation:
Department of Oceanography, University of Southampton, Southampton SO9 5NH, UK

Abstract

Discrepancies between clay mineral and organic indicators of very low-grade metamorphism have been observed from the Southern Uplands of Scotland. In the Southern Belt, I-S expandability ranges from 18–5% and chitinozoan reflectance from 0·8–2·1% R0 mean; a clear correlation exists between I-S expandability and organic maturity. At Dob's Linn in the Central Belt, I-S expandabilities range from 18–10%, and chitinozoan reflectance from 3·6–4·8% R0 mean. The results from Dob's Linn show anomalously high I-S expandabilities with respect to maturity, both in comparison with the Southern Belt and with previous work from other regions. K-feldspar is present in variable amounts in the Southern Belt, but is not detectable by XRD at Dob's Linn. Low K+ activity is believed to have resulted in a slower reaction rate at Dob's Linn, and a consequent “lag” in I-S expandability with respect to the Southern Belt.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1991

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