The Cheviot Andesites
Within the main body of the Cheviot Hills Andesite
lavas there are occasional flows that are almost wholly unaltered and have
become known as glassy andesites, their freshness distinguishing them from the “normal” (altered) type. In thin section they show phenocrysts
of unaltered labradorite (a plagioclase feldspar), together with augite and rhombic pyroxene, the latter two having undergone som degree of chloritisation.
The groundmass is composed of fresh feldspathic material and brown glass.
The thin section here is from a sample collected from the Coquet Valley at the sharp bend of the river GR:845113) at Carshope.
(from “A Guide to the Geology of the Cheviot Hills” , D.A.Robson. Trans. Nat. Hist. Soc. Northumbria Vol. 43, No.1)
Cheviot andesite ppl
Cheviot andesite xpl
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