Petrography and low grade metamorphism of an Ordovician pelite from the Fishguard district, Wales, 1:50k sheet 210

摘要

This report describes the results of a petrographic and X-ray diffraction study of a single pelite sample collected as part of the geological survey of the Fishguard, Wales 1:50k sheet 210. A Kubler Index of 0.41 from XRD analysis indicates that the pelite has just reached the low anchizone grade of low grade metamorphism. Backscattered scanning electron microscopy of a polished thin section of the pelite reveals evidence of sedimentary lamination, a penetrative cleavage and later Fe-oxide veining. Such findings are in keeping with previous illite crystallinity surveys of the Welsh Basin.