Assessment of the potential for gold mineralisation in the Southern Uplands of Scotland using multiple geological, geophysical and geochemical datasets

Geological, geophysical and geochemical datasets for the Southern Uplands of Scotland have been combined and evaluated to enable selection of areas potentially favourable for the occurrence of gold mineralisation. Datasets utilised comprise 1) residual polar aeromagnetic anomalies, 2) residual Bouguer gravity anomalies, 3) lineations derived from images of the aeromagnetic and gravity data, 4) the distribution of igneous rocks and agglomeratic volcanic vents, 5) mapped fault vectors, 6) significant deviations from the regional strike of the Lower Palaeozoic rocks, 7) the distribution of arsenic, antimony, bismuth, copper, lead, silver and nickel in minus 15Opm stream sediment samples and S) the locations of known gold occurrences in rock and alluvium. Three primary target areas, together with 19 smaller secondary target areas, were identified covering a range of different combinations of geological, geophysical and geochemical features. Particular attention was paid to 1) areas where widespread strike deviations were possible indications of anomalous relative tensional stress fields which could favour mineralisation, 2) intersections and foci of geophysical lineations and 3) small groups of arsenic and antimony anomalies which could indicate centres of minor intrusive igneous activity. Reconnaissance drainage and rock samples were collected at the three primary target areas and, on a smaller scale, at eight secondary target areas. In one of the primary target areas, south-east of Moffat, widespread gold was found in drainage in the Glengap Bum, a tributary of the Wamphray Water. A level of 2.23 ppm gold was recorded in a sample of brecciated and altered red greywacke siltstone from the stream. Gold was also found in drainage samples from adjacent catchments. Electron microprobe characterisation of gold grains from this area showed severaI to be rich in palladium and therefore similar to grains found in association with the contact between Permian red beds and underlying Lower Palaeozoic rocks in the Thomhill area, to the north of Dumfries. In another of the primary target areas, gold was found in drainage on two sides of Stob Law to the south of Peebles. The small number of rock samples from this area contained up to 59 ppb gold and 17 19 ppm arsenic. In the third primary target area, Laurieston Forest, west of Castle Douglas, minor amounts of gold were found in drainage, probably derived from a north-west-trending structure and in veined greywacke (65 ppb gold). The drainage data from this areas also provided evidence for the occurrence beneath drift of a centre of hydrothermal activity with which some gold may be associated. Significant amounts of alluvial gold were also found in three of the secondary target areas, Hawkshaw Burn and Auchencat Burn, to the north of Moffat, and Hopes Water, south of Haddington. Lesser amounts of gold were found in two other secondary target areas, Little Clyde Forest, north-west of Beattock and Glencotho, west of Tweedsmuir. The results of the test sampling of targets identified by interpretation of the multiple datasets are sufficiently promising in the Glengap Bum, Stob Law area, Hawkshaw Bum, Auchencat Bum and Hopes Water to merit follow-up investigations to define and assess the source of alluvial and bedrock gold. Such findings indicate that the approach used in this study to the identification of promising targets for gold mineralisation within one geological terrane is valid and merits further testing and development.