Proximal Cu + Zn exhalites in the Argyll Group Dalradian, Creag Bhocan, Perthshire

Synopsis Stratabound Cu + Zn mineralization at Creag Bhocan, near Tyndrum, represents the proximal equivalent of previously reported distal exhalites in the Ben Challum Quartzite of the Argyll Group Dalradian. The Creag Bhocan mineralization is characterised by pyrite, chalcopyrite and sphalerite hosted by chloritic schists and albitic quartzites. Mineral inclusions within syngenetic pyrite suggest ore formation at temperatures between 250°C and 350°C from reducing, acidic (pH3–5) hydrothermal fluids, in which H 2 S was the dominant aqueous sulphur species. Affinities with the volcanic-associated massive sulphide (VMS) group of deposits are suggested for the Creag Bhocan mineralization. High heat flow and minor intrusives associated with crustal extension are thought to have driven the circulation system, and the mineralization within the Ben Challum Quartzite as a whole has many characteristics similar to those of Besshi-type deposits.