FIGURE 4.

Scanning electron microscopy (SEM) images of weathered inactive sulfide chimney surfaces (WSS1, WSS3, and WSS15). (a,b) Dense aggregates of FeOB-associated ultrastructures such as twisted ribbon-like stalks, branched stalks, straight tubular sheaths and contorted filaments. (c–f) Typical morphologies of Fe-rich ultrastructures induced by known FeOB species. Yellow crosses indicated the positions for EDS analyses. (g) Locally, some branched stalks are heavily encrusted by Fe precipitates. (h) Magnified images of stalk surfaces with tiny needlelike textures. (i,j) Stalks encrusted by bladelike Fe precipitates. Chemical compositions of bladelike textures (yellow cross) was analyzed with EDS. (k) Common occurrence of freshly biogenic stalks and “modified” stalks by abiogenic Fe precipitates. (l,m) EDS spectra of FeOB-associated stalks marked with yellow cross in (c,f), respectively. Iron was the dominant chemical compositions (>50 wt%), followed by variable amounts of C and Si. (n) Chemical contents of needle-like and flower-like architectures in (j) which are mainly composed of Fe.