Low-Temperature Fluorocarbonate Mineralization in Lower Devonian Rhynie Chert, UK

John Parnell* (Corresponding Author), Temitope O. Akinsanpe, John W. Still, Andrea Schito, Stephen A. Bowden, David K. Muirhead, Joseph G. T. Armstrong

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)
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Rare earth element (REE) fluorocarbonate mineralization occurs in lacustrine shales in the Lower Devonian Rhynie chert, Aberdeenshire, UK, preserved by hot spring silicification. Mineralization follows a combination of first-cycle erosion of granite to yield detrital monazite grains, bioweathering of the monazite to liberate REEs, and interaction with fluorine-rich hot spring fluids in an alkaline sedimentary environment. The mineral composition of most of the fluorocarbonates is referable to synchysite. Mineralization occurs at the surface, and the host shales subsequently experience maximum temperatures of about 110 ℃. Most fluorocarbonate mineralization originates at much higher temperatures, but the Rhynie occurrence emphasizes that low-temperature deposits are possible when both fluorine and REEs are available from granite into the sedimentary environment.
Original languageEnglish
Article number595
Number of pages17
Issue number5
Early online date25 Apr 2023
Publication statusPublished - 25 Apr 2023

Bibliographical note

Funding: J.G.T.A was partially funded by the Natural Environment Research Council, grant number NE/T003677/1.
Acknowledgments: We are grateful to W. Ritchie, J. Johnston, and J. Bowie for skilled technicalsupport. Samples were archived by N.H. Trewin, C.M. Rice and S. Fayers.


  • rare earth elements
  • synchysite
  • Rhynie chert
  • Scotland
  • hot spring


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