Fig 1.
Fungal mycelium and botryoidal Mn oxides in a vug.
(A) Optical microphotograph of a vug in basalt lined with a fossilized biofilm of montmorillonite from which fungal hyphae protrude to form a mycelium. Black patches are botryoidal Mn oxides. (B) ESEM image of a vug lined with fossilized biofilm from which hyphae protrude forming a mycelium. Closely associated with the mycelium are black patches of botryoidal Mn oxides. (C) ESEM image of botryoidal Mn oxides. Black arrow show the border of the Mn oxide, note the change in grayscale between the Mn oxide and the underlying montmorillonite. (D, E) ESEM images showing botryoids on the basal parts of hyphae (white arrow). Legend: bf, biofilm; my, mycelium; bmo, botryoidal Mn oxide; hy, hyphae.
Fig 2.
Raman spectrum of the fossilized biofilm.
Raman spectrum (black) of the material that has fossilized the biofilm and hyphae is identified as Fe-rich smectite of the montmorillonite-nontronite series after comparison with RRUFF reference spectra [25]. The obtained bands are close to those of nontronite (reference spectrum in red), but exhibit small differences in peak positions. The spectrum is complex and an alternative interpretation is that the material is montmorillonite (reference spectrum in blue) and that the spectrum is influenced by the presence of small amounts of FeOOH, probably lepidocrocite (reference spectrum in green).
Table 1.
EDS data given in wt%.
Fig 3.
Cross sections through botryoidal Mn oxides and related sporophores.
(A) Optical microphotograph of a vug with cross section through a botryoidal structure. (B) Magnified and focused part of A showing the cross section of the botryoidal Mn oxide with vague layering at the margin and sporophore-like structures on top. Black mineralized feeder veins are seen underneath the botryoidal structure. White arrows show Mn oxides formed underneath the fossilized biofilm. (C) ESEM image of a cross section through a botryoidal structure showing vague layering at the top margin and sporophores formed as separate cells stacked on each other. (D) ESEM image of a cross section through a botryoidal structure and the distribution of sporophores on its top. (E) Detailed ESEM image of D showing sporophores both made up of separate cells and terminal swelling. (F) ESEM image showing sporophores made up of separate cells and with terminal swelling. Legend: sp, sporophore; spc, sporophore with separate cells on top of each other; spts, sporophores with terminal swelling; la, layering; fv, feeder veins.
Fig 4.
Raman spectrum of the botryoids.
Raman spectrum (black) of the botryoidal structure identified as todorokite after comparison with RRUFF reference spectra of manganese dioxides from Downs (2006).
Fig 5.
EPR spectra of the todorokite.
Fig 6.
EPR spectra for abiotic Mn oxide.