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

Tim Dempster and Scott A. Jess
Ikaite pseudomorphs in Neoproterozoic Dalradian slates record Earth's coldest metamorphism
Journal of the Geological Society of London (July 2015) 172 (4): 459-464

Abstract

Calcite pseudomorphs have replaced euhedral ikaite (CaCO (sub 3) .6H (sub 2) O) 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 subaerially 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.


ISSN: 0016-7649
EISSN: 2041-479X
Coden: JGSLAS
Serial Title: Journal of the Geological Society of London
Serial Volume: 172
Serial Issue: 4
Title: Ikaite pseudomorphs in Neoproterozoic Dalradian slates record Earth's coldest metamorphism
Affiliation: University of Glasgow, School of Geographical and Earth Sciences, Glasgow, United Kingdom
Pages: 459-464
Published: 201507
Text Language: English
Publisher: Geological Society of London, London, United Kingdom
References: 56
Accession Number: 2015-084878
Categories: Igneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus.
N56°23'60" - N56°23'60", W05°31'60" - W05°31'60"
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 201536
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