Silica Precipitation in Fractures and the Evolution of Permeability in Hydrothermal Upflow Zones

Analytical models are used to compare the rates at which an isolated fracture and vertical, parallel fracture sets in hydrothermal upflow zones can be closed by silica precipitation and thermoelastic stress. Thermoelastic sealing is an order of magnitude faster than sealing by silica precipitation. In vertical fracture sets, both the amount of silica precipitation resulting from cooling and the total thermal expansion of the country rock may be insufficient to seal cracks at depth. These crack systems may ultimately close because the pressure dependence of silica solubility maintains precipitation during upflow even after the temperature gradient vanishes.

[1]  W. Brace.  Permeability of crystalline and argillaceous rocks , 1980 .

[2]  T. Hewett,et al.  Fluid convection and mass transfer in porous sandstones—a theoretical model , 1982 .

[3]  P. Lichtner.  The quasi-stationary state approximation to coupled mass transport and fluid-rock interaction in a porous medium , 1988 .

[4]  R. Lowell.  Modeling continental and submarine hydrothermal systems , 1991 .

[5]  H. Taylor,et al.  Quantitative Simulation of the Hydrothermal Systems of Crystallizing Magmas on the Basis of Transport Theory and Oxygen Isotope Data: An analysis of the Skaergaard Intrusion , 1979 .

[6]  H. Barnes,et al.  Geochemistry of Hydrothermal Ore Deposits , 1968 .

[7]  L. Germanovich,et al.  Percolation Theory, Thermoelasticity, and Discrete Hydrothermal Venting in the Earth's Crust , 1992, Science.

[8]  M. Ghiorso,et al.  Coupled fluid flow and reaction in mid-ocean ridge hydrothermal systems: The behavior of silica , 1991 .

[9]  Peter C. Lichtner,et al.  Continuum model for simultaneous chemical reactions and mass transport in hydrothermal systems , 1985 .

[10]  R. Lowell.  Thermoelasticity and the formation of black smokers , 1990 .

[11]  G. Kennedy.  A portion of the system silica-water , 1950 .

[12]  M. Fisk,et al.  Major off-axis hydrothermal activity on the northern Gorda Ridge , 1990 .

[13]  R. Fournier,et al.  An equation correlating the solubility of quartz in water from 25° to 900°C at pressures up to 10,000 bars , 1982 .

[14]  D. White,et al.  Silica in hot-spring waters , 1956 .

[15]  R. Fournier.  A method of calculating quartz solubilities in aqueous sodium chloride solutions , 1983 .

[16]  R. Lowell,et al.  Mathematical modeling of conductive heat transfer from a freezing, convecting magma chamber to a single-pass hydrothermal system: implications for seafloor black smokers , 1991 .

[17]  H. Helgeson,et al.  Evaluation of irreversible reactions in geochemical processes involving minerals and aqueous solutions - I. Thermodynamic relations , 1968 .