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°C and pH of 1–3. These structures are formed of irregular sequences of silicified Cyanidium mats, silicified Alicyclobacillus 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.