This research has been carried under the Geological Survey Ireland 2017 Short Call. This call provided funding for researchers in academia or industry on the island of Ireland for projects of less than 12 months duration and less than €25,000.
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Lead Applicant: Dr Sean McClenaghan
Host: Trinity College Dublin
Project Title: Resolving the paragenesis of precious metals in the Avoca District: implications for late orogenic gold at Kilmacoo, Co Wicklow
Project Description: Lower Palaeozoic volcanogenic massive sulphides in the Caledonian terrane of southeast Ireland offer an ideal setting for the study of complexly-deformed mineral deposits, where geochemical zonation and mineral textures are discernible through the overprinting effects of orogenesis. The effects of syn-metamorphic deformation on sulphide assemblages are important for the concentration of ore resources, resulting in structural thickening and attenuation, as well as possible secondary mobilization and enrichment from later orogenic fluids. Sulphides in the Avoca District exhibit both cataclastic and fluid-assisted plastic deformation textures, and recrystallization (coarsening) in response to variable lower to middle-greenschist facies metamorphism. This has also had an effect on mineral chemistry, with the re-equilibration of major elements in sphalerite and arsenopyrite, and the heterogeneous distribution of trace-elements across multiple phases of pyrite. Advancements in micro-analytical techniques now allow for detailed trace-element mapping of sulphide phases (pyrite), which can reveal much of the complex interplay between fluids and mineral growth, resolving the mineral paragenesis for metamorphosed VMS deposits. With the siting of precious metals in the Avoca deposit and Kilmacoo Au occurrence not fully discerned, this study aims to characterize the form and distribution of gold to assess the extent of syn-tectonic enrichment during the Caledonian Orogeny.