Mantle-derived heat recorded by conodont colour alteration in the Carboniferous of the Isle of Man
✍ Scribed by A. Swift
- Publisher
- John Wiley and Sons
- Year
- 1993
- Tongue
- English
- Weight
- 530 KB
- Volume
- 28
- Category
- Article
- ISSN
- 0072-1050
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✦ Synopsis
A range of colour alteration index (CAI) values between 3.0 and 6.0 is recorded for conodont elements recovered from the Arundian to Brigantian (Dinantian, Lower Carboniferous) sequence around Castletown, Isle of Man. Mantlederived heat, channelled through the Caledonian South Barrule pluton, is proposed as the major cause of these elevated values. A lower CAI of 2.5 is obtained from elements recovered from a borehole sunk into the concealed Namurian (Upper Carboniferous) deposits near Shellag Point; the Glen Mona pluton acted as the medium for mantlederived heat in this instance. The CAI values which may have been established during a late Dinantian volcanic episode around Castletown were overprinted by the greater effects of heat emanating from the South Barrule pluton. The record of CAI 6.0 for a sample taken from the immediate vicinity of a dyke indicates a high level of very localized CAI elevation in the early Tertiary.
KEY WORDS Colour alteration index Conodonts Isle of Man carboniferous Plutons Mantle-derived heat