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The Flybye Springs, Northwest Territories, consist of 10 active vents and numerous small seeps that discharge sulphide- and barium-rich spring waters at an average temperature 8.5 °C. Oxidation of sulphide to sulphate drives precipitation of stellate and platy barite microcrystals in the proximal flow paths. Downstream, and in vent- and tributary-fed ponds, barite is precipitated among streamer and mat forming colonies of sulphur-tolerant microbes, including Thiothrix, Beggiatoa, Thioploca, Chromatium, Oscillatoria, fungi (dominantly Penicillium), and unicellular sulphate reducing bacteria. These microbes mediate barite saturation by adjusting redox gradients and via passive adsorption of barium ions to cell surfaces and extracellular polymeric substances. Passive biomineralization produces barite laminae in floating microbial mats, nanometric coatings, and micrometric encrustations around microbial cells and filaments, and local permineralization of Thiothrix, Beggiatoa, and Oscillatoria outer cell walls. Intracellular barium enrichment and (or) metabolic sulphur oxidation may be important to "active biomineralization" that produces nanometric barite globules on the tips of fungal hyphae, barite-filled cell cavities in Beggiatoa and Thiothrix, and baritized sulphur globules. Degradation of biomineralized cells generates detrital "microfossils," including barite tunnels, layered cylinders, solid cylindrical grains and chains of barite beads. The diversity of inorganic and biomineralized barite in the Flybye Springs flow path highlights the influence of ambient chemistry, microbial metabolism, and cellular structure on barite solubility and on the taphonomy of microfossils preserved in barite.

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Barite precipitation was induced by mixing sulfate and barium solutions to investigate conditions under which barite is most likely to be localized on microbial substrates, and hence most likely to preserve biogenic textures. Addition of sulfate solution to barium solution resulted in precipitation of intergrown platy, dendritic ''angel wing,'' and microgranular barite in solution. Bacterial streamers and extracellular polymeric substances (EPS) collected from a cold sulfur spring acted as loci for precipitation of euhedral bowtie, intergrown platy, and intergrown tabular barite crystals, and scalloped platy barite crystals when sulfate solution was added to barium solutions in which they were immersed. Desiccation of bacterial streamers previously exposed to barium solution also produced subhedral platy and elongate anhedral barite crystals on extracellular surfaces and EPS. Immersion of barium-exposed streamers in sulfate solution produced scalloped platy barite crystals distributed through EPS and forming radial strings around bacterial filaments. Accidental exposure of streamers to iron produced amorphous iron oxides, as well as novel single and intergrown mixed-oxygenation-state barite/FeS ''sandwiches.'' Distinct barite crystal habits and textures were observed in experiments conducted with and without bacterial streamers, suggesting that microbes have potential to influence the petrography of barite precipitated in sulfate-limited microbially colonized environments.

At the Miette Hot Springs site, relict tufa stretches for nearly 500 m along the west side of Sulphur Creek valley and rises up to 30 m above the valley floor. The tufa, composed of low-Mg calcite, precipitated from waters discharged from a line of perched springs.14C dating of bone material embedded in the tufa indicates that tufa precipitation took place between ~4500 and 2500 years BP under cool and moist climatic conditions. The spring biota was dominated by filamentous microbes (mainly Phormidium and Oscillatoria), with fewer diatoms (including Cymbella), testate protozoans (including Quadrulella), ostracodes (including Darwinula, Heterocypris, Cadonia, and Cyclocypris), and various bryophytes. The ecological preferences of these microbes indicate that the spring water had near-neutral pH, was Ca, HCO3, and H2S–SO4rich, and emerged at 50–65 °C. Landslides disrupted the west wall of Sulphur Creek valley during and after tufa growth. The relict tufa is divided into six morphotypes that reflect variations in water flow down the steep and rugged flow path. Domal tufa is located around the spring vents, roll-over tufa developed where water flowed over sharp lips or structural barricades, vertical tufa formed where calcite was precipitate from water flowing down steep to vertical inclines, flat-banded tufa reflects precipitation on a gentle slope, and wedge-shaped tufa formed where more rapid downslope calcite precipitation caused a progressive decrease in slope. The tufa contains stromatolitic facies (including streamer, porous laminar, dense laminar) and nonstromatolitic facies (bedded, crenulated) that reflect variations in the biology, water temperature, and style of flow of different parts of the spring flow path.