Constraining the source of detrital gold in the Duns area, Berwickshire, Scotland

Particles of gold panned from two sites within the Duns area of the Southern Uplands of Scotland are larger by an order of magnitude than those previously reported from the adjacent Lammermuir Hills. The Southern Uplands Down Longford Terrane is geologically diverse and potential local sources include orogenic, intrusion-related, red-bed and palaeoplacer models. The populations at both sites are morphologically and microchemically similar. Morphogenetic analyses of the particles suggest distances from source do not exceed 7.5 km. A minority of the particles panned (containing up to 99% Au with trace Pd, inclusions with Pd to 22.2 wt% and Hg to 13.7 wt%) were chemically identical to those previously reported from the adjacent terrane and attributed to red bed styles of gold mineralisation. We also report the discovery of a stockwork, from where detrital gold contained Bi-Te inclusions, which suggests a local magmatic source. However, most of the particles had Ag contents of up to 46 wt%, more typical of an orogenic source. Favourable geochemical conditions within SUDLT basinal muds regionally may indicate that the basins in this terrane were fertile for the capture and concentration of orogenic gold.