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

Tim Dempster, Scott A Jess

Research output: Contribution to journalArticle

6 Citations (Scopus)

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 languageEnglish
Pages (from-to)459-464
Number of pages6
JournalJournal of the Geological Society
Volume172
Issue number4
Early online date3 Jun 2015
DOIs
Publication statusPublished - Jun 2015

Fingerprint

ikaite
Dalradian
porphyroblast
metamorphism
geothermal gradient
permafrost
unconformity
glaciation
folding
bedrock
penetration
calcite
tectonics
rock
cold

Keywords

  • Ikaite
  • Snowball Earth
  • Glendonite
  • Dalradian supergroup
  • Easdale Slates

Cite this

Ikaite pseudomorphs in Neoproterozoic Dalradian slates record Earth's coldest metamorphism. / Dempster, Tim; Jess, Scott A.

In: Journal of the Geological Society , Vol. 172, No. 4, 06.2015, p. 459-464.

Research output: Contribution to journalArticle

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