Re os dating pyrite
Recent paleomagnetic data from Lisheen have been interpreted to indicate post-Variscan epigenetic mineralization at ca.
277 Ma, much younger than previously proposed and in apparent contradiction with Variscan thrust deformation of the ores.
The Re-Os ages overlap with the ages of lower Carboniferous volcanic rocks in the Midlands, which are the product of magmatism that has been invoked as the driving force for hydrothermal activity.
The relatively low initial Os ratios for both Lisheen (0.253 ± 0.045) and Silvermines (0.453 ± 0.006) are compatible with derivation of Os from these magmas, or from the Caledonian basement that underlies the ore deposits.