The golden conundrum of Loch Tay, Scotland
A webinar hosted by the Leeds Geological Association
presented by
Shane Webb (School of Earth and Environment, University of Leeds)
21st April, 19:15
Commemorative coins made by Scotgold in 2016 from gold mined at Cononish. Photograph: Scotgold Resources
In recent years, gold has successfully been poured at Scotland’s first commercial gold mine, Cononish. The commercial viability of this deposit has led to renewed interest in occurrences of other occurrences of gold mineralisation in the Scottish Grampians, including Loch Tay, which hosts multiple gold and base metal targets along its southern margins. These mineral deposits have numerous enigmatic characteristics, and an overarching model to explain their formation remains lacking. Historically, Scottish and Irish gold deposits have been considered to be ‘orogenic’, meaning they formed as a result of fluid release during metamorphism. Orogenic gold deposits are usually found within deformed metasediments in association with crustal-scale strike-faults. This geological setting typifies the gold deposits around Loch Tay. However, these mineral veins contain very high concentrations of other metals (lead, zinc and copper), which is unusual for orogenic gold deposits and isotope values also imply that mantle-derived fluids have been involved in their formation. Orogenic processes cannot solely explain the Loch Tay mineralisation. The fundamental problem in trying to understand the ore-forming processes at Loch Tay lies in the fact that the age of the veins remains unknown. It is therefore impossible to link the age of mineralisation to any of the geological events that happened during the Caledonian Orogeny. However, dating the veins has proven to be very challenging. This presentation will provide an overview of how geologists may overcome issues relating to geochronology and illustrate how the easiest questions that can be asked (‘how old is this mineral vein?’) can sometimes be the hardest ones to answer.
This event will be held using Microsoft Teams please contact the LGA’s secretary for a joining link