Abstract
Thermophilic microbes have long been implicated in the formation of travertine and siliceous sinter. Precipitation of CaCO3 at thermal springs is induced mainly through degassing of CO2. Cyanobacteria and other bacteria can play a role in calcite and aragonite nucleation in warm (20 – 40 °C) and mesothermal (40 – 75 °C) hot springs, and through photosynthesis and other biochemical processes may mediate some mineral precipitation. Many fabrics in warm-spring and mesothermal travertines preserve evidence of microbes. Travertine precipitated at hyperthermal (> 75 °C) spring vents is mainly abiotic and commonly exhibits high-disequilibrium crystal morphologies. Silica precipitation in hyperthermal springs and geysers results mainly from rapid cooling and evaporation. Microbes, however, can play an important role by providing templates for silica nucleation and by controlling development of many sinter and geyserite fabrics.
Published Version
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