Figure 4
Sampled spire from Politeia Vent Complex and SEM-BSE micrographs of hydrothermal precipitates with fragile morphologies (sample NA014-003).
Upper part: (a) Basal cross section of sulphide-sulphate spire showing a thick porous “inner sulphide-sulphate core” (ISSC) (b) (surrounded by an earthy thin orange-yellow outer As-sulphide-dominated layer (OAsL) (c) that grades into an orange to brown Fe-(hydrated)-oxyhydroxide-dominated microbial surface Fe crust (SFeC) (d). Unidentified dark-violet phases similar to Sb-Zn-S phases are lining interior porous conduit network (e). PXRD patterns for b, c and d are also shown. Bottom part: (b) SEM image of barite laths and rosettes forming a substrate for disseminated sulphides of mainly colloform banded pyrite (py). (c) Overview of amorphous orpiment (As2S3)-type (characterized by XAFS) phase morphologies, including clustered microspheres and globular aggregates of various sizes(1-10 μm) and straight, curved and branching filaments with ringed grooves (white arrows), overlying layer of barite blades. (d) Amorphous ferrihydrite-type (characterized by XAFS) Fe-(hydrated) -oxyhydroxides occurring as laterally extensive slime-like material (sli), locally perforated by holes (ho), forming an intimate extension of straight and/or curved filamentous, coccoidal, rod-shaped and long straight stick structures. (e) Overview of Sb-Zn-S phase morphologies including curved and twisted hair-like filaments entwined with each other forming dense arrays and colonizing barite crystal face (ba). A large variation in additional accumulation of oblate or imperfect aggregated microspheres developed on the surface of filaments can been seen.
