Ikaite pseudomorphs in Neoproterozoic Dalradian slates record Earth’s coldest metamorphism

Dempster, T. and Jess, S. A. (2015) Ikaite pseudomorphs in Neoproterozoic Dalradian slates record Earth’s coldest metamorphism. Journal of the Geological Society, 172, pp. 459-464. (doi: 10.1144/jgs2015-018)

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Abstract

Calcite pseudomorphs have replaced euhedral ikaite (CaCO3.6H2O)porphyroblasts in Dalradian calcareous slates and metadolostones of western Scotland, with a volume decrease of at least 47%. Porphyroblast-fabric relationships indicate that the initial growth of ikaite post-dates a penetrative tectonic fabric developed during upright folding. This is the first reported occurrence of metamorphic ikaite porphyroblasts and points towards growth within the slates during an ultra-low temperature metamorphism with an exceptionally low geothermal gradient. This event is associated with the penetration of long-lived and extreme permafrost deep into sub aerially exposed bedrock during Neoproterozoic glaciation. The presence of the well preserved pseudomorphs within the Easdale slates of the Argyll group implies that a Neoproterozoic orogenic unconformity exists above the stratigraphic position of theserocks.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Dempster, Dr Tim
Authors: Dempster, T., and Jess, S. A.
College/School:College of Science and Engineering > School of Geographical and Earth Sciences
Journal Name:Journal of the Geological Society
Publisher:Geological Society of London
ISSN:0016-7649
ISSN (Online):2041-479X
Copyright Holders:Copyright © 2015 Geological Society
First Published:First published in Journal of the Geological Society 2015
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher.

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