The Rhynie Chert (Figure 1) is a Lower Devonian (∼407 Ma) lagerstätte of early plants and their accompanying biota (Strullu-Derrien et al., 2014;Trewin & Fayers, 2015), preserved by early silicification from adjacent hot spring activity (Baron et al., 2004). The deposit constitutes the world's oldest preserved terrestrial ecosystem, including extensive evidence for the colonization of plants by mycorrhizal fungi (Harper et al., 2020;Krings et al., 2018;Strullu-Derrien et al., 2014;Taylor et al., 2004). Arbuscular mycorrhizal fungi evolved in symbiosis with early plants which were colonizing the Devonian land surface (Remy et al., 1994). The plants require trace elements, supplied by the fungi, while the fungi gain carbon from the photosynthesizing plant. Fungi similarly controlled nutrients that were required by animals in the Rhynie ecosystem (Strullu-Derrien et al., 2016). Fungi also contribute to plant resistance against contaminating trace elements (Colpaert et al., 2011;Hildebrandt et al., 2007;Neidhardt, 2020). It is important to note that much current work on the fungal response to metals relates to ectomycorrhizal or ericoid mycorrhizal fungi, which had not evolved at the time of Rhynie Chert deposition. This includes numerous studies on the fungus Aspergillus. However, there is also evidence that arbuscular mycorrhizae, which were present at Rhynie, influence the occurrence and speciation of numerous trace elements,

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.

Copper, uranium, and rare earth element (REE) mineralisation occurs in hydrocarbon-bearing Devonian continental sandstones in southwest Orkney, Scotland. The aeolian Yesnaby Sandstone Formation and fluvial Harra Ebb Sandstone Formation were mineralised following oil emplacement. The REE-bearing APS mineral florencite is particularly associated with bituminous nodules, many of which contain brannerite. Subsequently hydrothermal copper and other sulphides, and barite, further mineralised the oil reservoir at a temperature of ~190 °C. Oil was mobilised through mineralised fractures at this stage. Biodegradation of the oil occurred later, following the Carboniferous-Permian uplift. The occurrence confirms that Cu-APS mineralisation is possible in relatively low-temperature regimes in sedimentary basins.