The growth of siliceous sinter deposits around high-temperature eruptive hot springs

Siliceous hot spring deposits (sinter) are of interest as they are indicative of hydrothermal resources at depth and may provide evidence for early life on Earth and possibly Mars. Numeric models of concurrent evaporation and opal-A precipitation around high temperature (>73 degrees C), eruptive hot spring vents such as geysers show that silica is most efficiently precipitated by complete evaporation owing to very sluggish growth kinetics for silica precipitation from supersaturated hydrothermal water. Where evaporation is complete between geyser events, areas of initially deeper water precipitate more silica that, over time, fill in topographic lows to produce a smooth surface. In contrast, incomplete evaporation, in which water is left in low areas prior to being washed away by the next geyser event (or equivalently where there is continuous surface flow in topographic low areas), tends to enhance the growth of minor topographic highs and leads to an increase in surface roughness such as seen in the development of "knobby" geyserite sinter texture around vents. (C) 2012 Elsevier B.V. All rights reserved.