Metallogeny of the Loch Tay area (Central Scotland) from gold compositional variations, vein parageneses and structural constraints

Deciphering the metallogeny of auriferous mineralisation in orogenic belts can often be challenging, due to the potential interplay of genetically distinct hydrothermal processes associated with it and complications that might arise from the discontinuity or lack of visible mineralised outcrops at the exploration stage.
The Loch Tay area of Central Scotland is a host of both gold-bearing hydrothermal veins and widespread placer gold populations. However, the genetic relationships between these types of auriferous occurrences as well as the associated mineralization style(s) have been long unresolved. This can be achieved by combining gold compositional signatures and hydrothermal vein paragenetic histories with an understanding of the local structural/tectonic context. The proposed approach has been implemented to understand the metallogeny of the area and facilitate predicting the nature of possible undiscovered auriferous mineralisation.
In situ mineralization at Calliachar Burn, River Almond and Coire Buidhe records the temporal overlap of separate fluid pulses and at least two gold input events. At the Lead Trial, vein textures and internal variations in the gold alloy composition support the hypothesis of a low-sulphidation epithermal system and evolving nature of the mineralising fluids. In all cases, the range of compositional signatures (alloy and inclusion suites) exhibited by particle populations from alluvial localities is larger than that observed in local eluvial and in situ samples, suggesting subtle variation in mineralogy within geographically proximal and genetically related vein systems. Additionally, the compositional signatures of gold populations from the South of the area (e.g., Glen Lednock and Keltie Burn, for which only placer samples were analysed) indicate derivation from porphyry and low-sulphidation epithermal environments, respectively. The multi-scale and multivariate approach that is adopted for this study may find successful application in other similar ore-related settings worldwide.