precipitates contain up to 2 % P2O5. The mobilization of Mn, Fe and P are all features of mycorrhizal nutrient concentration. However, the ecosystem was also exposed to toxic elements from hot spring hydrothermal activity. The oxide precipitates include titanium and iron-titanium oxide which sequestered potentially toxic tungsten and antimony. Abundant pyrite framboids in the Rhynie Chert indicate that plant decomposition included microbial sulphate reduction. This caused the removal of some of the arsenic from the groundwaters into the pyrite, which reduced toxicity while leaving enough for putative arsenic metabolism. These relationships show the mineral component of the ecosystem modified the geochemistry of ambient waters.
JGTA is supported by the Natural Environment Research Council (grant NE/T003677/1). Samples were archived at the University of Aberdeen by N.H. Trewin, S.R. Fayers and C.M. Rice. Skilled technical support was provided by J. Johnston, J. Bowie, W. Ritchie and C. Taylor. We are grateful for the comments of two reviewers which improved the manuscript.
Data Availability StatementData reported in Tables 1–3 is managed by the University of Aberdeen (https://doi.org/10.20392/eed913d7-12eb-4c5d-a276-e1920eecd43f).
- Rhynie Chert
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Jörg Feldmann (Participant), Andrew Alexander Meharg (Participant), Andrea Raab (Participant) & Eva Maria Krupp (Participant)