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Hydrothermal Transport and Deposition of Silica

Description: The strong Si-O-bond under dry conditions and in absence of impurities needs high activation energy for mobilization. Chemical activation with water based on the reaction: SiO{sub 2(s)} + nH{sub 2}O{sub (g,f)} = SiO{sub 2} {center_dot} nH{sub 2}O{sub (g,f)} lowers the energy barriers remarkably. Under normal conditions the equilibrium is extremely shifted to the left, however at increased temperatures and water-pressures (hydrothermal conditions) the reaction may cause strong chemical transport. The efficiency (rate) of transport depends on the physico-chemical and physical parameters (temperature, pressure, viscosity e.g.) as well as on the mechanism of flow. The phase composition and micro-structure of the silica-deposit formed by the reverse process, strongly depends on the rate of transport and deposition and on temperature of the substrate.
Date: January 1, 1976
Creator: Florke, Otto W.
Partner: UNT Libraries Government Documents Department