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Ar/Ar dating of hydrothermal activity, biota and gold mineralization in the Rhynie hot-spring system, Aberdeenshire, Scotland |
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| Authors: | DF Mark CM Rice NH Trewin A Boyce |
| Institution: | a Scottish Universities Environmental Research Centre, Rankine Avenue, East Kilbride G75 0QF, UK b Department of Geology and Petroleum Geology, School of Geosciences, University of Aberdeen, Metson Walk, Aberdeen AB24 3UE, UK c School of Geographical and Earth Sciences, University of Glasgow, Gregory Building, Lilybank Gardens, Glasgow G12 8QQ, UK d Department of Geological Sciences and Geological Engineering, Queens University, Kingston, Ont., Canada K7L 3N6 |
| Abstract: | This study presents a new high-precision 40Ar/39Ar age for the Devonian hot-spring system at Rhynie. Hydrothermal K-feldspar sampled from two veins that represent feeder conduits and a hydrothermally altered andesite wall rock, date the hydrothermal activity, the fossilised biota, and syn - K-feldspar gold mineralization at 403.9 ± 2.1 Ma (2σ). Oxygen isotope data for the parent fluid (−4‰ to 2‰) show that the K-feldspar was precipitated from a dominantly meteoric fluid, which mixed with magmatic fluids from a degassing magma chamber.The 40Ar/39Ar age (403.9 ± 2.1 Ma 2σ]) when recalculated (407.1 ± 2.2 Ma 2σ]) with respect to the astronomically tuned age for Fish Canyon sanidine (28.201 ± 0.023 Ma 1σ]), also provides a robust marker for the polygonalis-emsiensis Spore Assemblage Biozone within the Pragian-?earliest Emsian. Furthermore, the age identifies the Devonian pull-apart volcano-sedimentary basins of the British and Irish Caledonides (and their root zones), as specific targets for future gold exploration. |
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