Evidence of a pre-tectonic origin for the auriferous vein-type mineralization of the Dolgellau gold belt, North Wales

Quartz-sulphide veins that cut Middle to Upper Cambrian sedimentary and int rusive rocks in coastal exposures at Friog, south of Fairbourne, Gwynedd, W ales, show features consistent with Acadian deformation, including folds, b oudins and cleavage. In the closely adjacent Dolgellau gold belt abundant q uartz-sulphide veins, some of which are auriferous, occur at the same strat igraphic level. Field examination of the gold-belt veins has revealed defor mational features similar to those exhibited at Friog. The textural and min eralogical similarities of the two occurrences of veining indicate that the y are both part of a regional set of veins that are pre-tectonic with respe ct to Acadian deformation-not post-Acadian, as was previously considered.