Fig 1.
Microphotographs of the fracture in sample (SMNH X5332). (A) Overview of the vein. (B) Showing parts of one side of the fracture after splitting. Dense fungal mycelia of yeast-like cells and hypha occasionally overgrown or intergrown by zeolites. Black arrow indicates the fungal mycelia preserved by montmorillonite, white arrows indicates specific hyphae.
Fig 2.
(A) Tomographic volume rendering of a multiple microstromatolite at the basalt-vesicle interface (SMNH X5333). (B,C) Tomographic slices of the microstromatolite in A at different levels. The internal structure is characterized by parallel layers in a stromatolitic pattern, and brighter bands towards the margins indicating higher densities. Note how the microstromatolite and surrounding basalt are overgrown by the biofilm and how hyphae protrude. (D) ESEM image of a zeolite crystal (SMNH X5334). A large incorporated microstromatolite is marked with an asterisk. (E) Microphotograph of the marked microstromatolite in D showing a cross section of the internal organization with marginal bands. (F) Microphotograph showing the internal structure of another microstromatolite (SMNH X5335) including layering and the dark marginal band that corresponds to the bright marginal band in SRXTM (compare with B and C). (G) ESEM image of a basalt sample with microstromatolites (SMNH X5336). Frame marks position of H. (H) Close-up of G showing the marginal band.
Fig 3.
Raman spectra of the microstromatolites.
Raman spectra in the spectral range 150–2000 cm-1 of the interior and the margin of a microstromatolite (SMNH X5335), shown in 2F. The spectrum from the margin shows bands that are attributed to hematite; a similar spectrum is obtained from the interior but with an additional band around 1600 cm-1 that indicates the presence of carbonaceous material. Reference spectra of hematite and carbonaceous material have been incorporated in the figure.
Fig 4.
Tomographic renderings of the basalt-clay-zeolite interface showing the biofilm and protruding hyphae.
(A–D) SRXTM isosurface (A), volume rendering (B, stereo anaglyph), and slices (C, D) of the cellular biofilm with protruding hyphae (SMNH X5337). The biofilm is partially overgrown by a zeolite crystal. Hyphae creeping along the mineral surfaces (arrows in A–C) leave a negative longitudinal cavity. Arrow in D points to base of the hyphae consisting of repetitive spherical cells that more distally transform into filamentous hyphae. (E,F) SRXTM isosurface (E) and volume (F) rendering showing how hyphae creep along the mineral surface (arrows) and/or branch where they protrude at the surface (right-hand arrows) (SMNH X5333).
Fig 5.
Powder XRD diffractogram of montmorillonite.
Note the change of basal reflection from 13 Å for dry sample (bottom) to 15 Å for moist sample (top), indicating basal swelling typical of montmorillonite. A relative low signal/noise ratio due to the small amount of available sample material.
Fig 6.
Raman spectra in the spectral range 100–4200 cm-1 of the zeolites that are identified as analcime, chabazite and natrolite after comparison with reference spectra in [27]. An idealized chemical composition is given for each zeolite mineral. Simplified characteristic wavenumber ranges for different Raman vibrational modes of the zeolite spectra are marked with different colours where green (<200 cm-1) is assigned to Ca-O and Na-O, blue (300–1200 cm-1) to Si-O and Al-O and red (1611 cm-1 and 3100–3700 cm-1) to O-H vibrations.
Fig 7.
Tomographic renderings of boring hyphae protruding on the zeolite surface (SMNH X5338).
(A) Volume rendering showing abundance of hyphae within a zeolite crystal and how they protrude at the mineral surface. Arrow at the left shows hyphae taking a path above the mineral surface; arrow to the right shows hyphae that branch at the point where they exit the mineral surface. (B) Isosurface rendering of left side of A showing a hypha taking a path above the mineral surface, occasionally touching it with short branches. (C, D) Volume rendering showing protruding hyphae that branch at the point where they exit the mineral surface, one branch creeping along the surface.
Fig 8.
ESEM (A–D) (SMNH X5339) and SRXTM (E) (SMNH X5340) images of fungi influencing the mineral surface.
(A) The influence of both yeast and hyphae on the mineral surface leaving negative pits. (B) The contact between two protruding hyphae and the zeolite surface. Note the rough and irregular texture of the mineral surface at contact compared to the normally smooth surfaces. (C) Hyphae protruding angularly and creeping along the mineral surface. (D) Hyphae creep along the mineral surface and their influence on the zeolite surface at contact. (E) Stereo anaglyph of an assemblage of cells within a zeolite crystal.
Fig 9.
Illustration of the successive colonization and mineralization in the fracture system.
(A) Colonization of the microstromatolites on the basalt. (B) Colonization of the fungal biofilm with yeast cells and hyphae, and subsequent overgrowth of the microstromatolites. (C) Partial zeolite overgrowth of the fungal community. (D) Hyphal growth outside and inside of the zeolite crystals. Fungal hyphae bore tunnel-like structures through the zeolite until they reach the mineral surface. At the zeolite surface, hyphae branch, creeps along the surface, occasionally touching it with short branches.
Fig 10.
(A) FTIR spectrum of chabazite single crystal showing bands caused by the chabazite structure. Sample thickness is ca 200 μm. The main band centred at 3500 cm-1 is caused by water molecules (crystal water), whereas the bands around 2100 and 4000 cm-1 are caused by crystal lattice overtones. Raman spectrum of the same chabazite crystal in Fig 6 confirms the absence of hydrocarbons and the presence of molecular water.
Fig 11.
Mössbauer spectrum of filamentous structures embedded in a zeolite crystal. Diamonds represent measured spectrum, thick solid line represents the sum of the two fitted doublets (thin lines) assigned to Fe3+. The obtained hyperfine parameters are similar to those reported for Fe-bearing montmorillonite [29].