Growth of siliceous spicules in acidic hot springs, Waiotapu geothermal area, North Island, New Zealand

摘要

Siliceous spicules, typically <= 3 cm high and <= 5 mm in diameter, are common just above water level alongside hot-spring pools and channels in the Waiotapu geothermal area of New Zealand, which contain waters of 50-80 degrees C and pH of 1-3. These structures are formed of irregular sequences of silicified Cyanidium mats, silicified Alicyclo-bacillus mats, and homogeneous opal-A laminae. Allochthonous microorganisms (e.g., diatoms) form a minor part of the silicified biota. Lamina boundaries are discontinuities that reflect pauses in opal-A precipitation. Barite, gypsum, and kaolinite crystals were precipitated on the spicule surfaces during these periods.