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 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.
Original language | English |
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Pages (from-to) | 459-464 |
Number of pages | 6 |
Journal | Journal of the Geological Society |
Volume | 172 |
Issue number | 4 |
Early online date | 3 Jun 2015 |
DOIs | |
Publication status | Published - Jun 2015 |
Keywords
- Ikaite
- Snowball Earth
- Glendonite
- Dalradian supergroup
- Easdale Slates