Life in Geothermal Systems a Key to Sinter Formation and Recognition?

Abstract

Siliceous particles, typically 10-30 long, were collected from near-neutral-pH chloride pools in Tokaanu, Waimangu and Waiotapu geothermal fields, New Zealand. occur in a variety of forms, described as lenticular, rectilinear, sigmoidal, rod, filament, tubule, sphere and irregular grains, and are most abundant at Tokaanu. Under the scanning microscope, the lenticular, rectilinear and sigmoidal forms are seen to have patterns of striations and lineations characteristic of pennate diatoms. Silica is the dominant component of the particles (75-96 as determined by semi-quantitativeSEM-EDAX analysis, frequently with significant chlorine (3-19 Aluminium is commonly present in minor quantities Sodium and potassium were rarely detected. The length-width aspect ratios and silica-chlorine ratios group the forms into the following associations: rectilinear; rod-filament and grain-sphere, with the tubule as an independent form. On the basis of morphological similarities with analogues, these groups are considered to be genetically distinct, representing diatoms, bacteria, inorganic particles and, possibly, filamentousalgae respectively.