Physical and Chemical Changes in Conodonts from Contact-Metamorphosed Limestones

Intensely-metamorphosed conodonts have been recovered from the aureoles of three basic intrusions in Northern England: the Little Whin Sill, the Beadnell Dyke, and the Holy Island Dyke. The colours displayed by these conodonts range up to Colour Alteration Index 8 of Epstein et al. (1977) as contact...

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Bibliographic Details
Published in:Irish journal of earth sciences 1988-01, Vol.9 (1), p.79-119
Main Author: Burnett, R. D.
Format: Article
Language:English
Subjects:
Acicular crystals
Apatites
Crystalline rocks
Crystallites
Crystals
Earth sciences
Earth, ocean, space
Exact sciences and technology
Fauna
Geology
Igneous and metamorphic rocks petrology, volcanic processes, magmas
Limestones
Metamorphism
Recrystallization
Surface texture
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Summary:Intensely-metamorphosed conodonts have been recovered from the aureoles of three basic intrusions in Northern England: the Little Whin Sill, the Beadnell Dyke, and the Holy Island Dyke. The colours displayed by these conodonts range up to Colour Alteration Index 8 of Epstein et al. (1977) as contacts are approached. Electron-microprobe investigations of the mineral phase (francolite) show only small changes in inorganic composition, the most significant of which is reduction in sodium content with increasing metamorphism. Scanning Electron Microscopy of metamorphosed conodonts reveals a consistent but form-variable sequence of structural alteration and recrystallization, related to enclosing sediment fabric, gross conodont morphology, and original microstructure.
ISSN:0790-1763
2009-0064