|Quartz with an exceptionally rich deposit of macroscopic|
This image from Nevada Outback Gems web page at
|A typical fault jog cavity, now filled with quartz|
From the referenced article.
Quartz solubility is strongly dependent on the density and pressure of the water in which it is dissolved. Such large pressure drops cause extreme supersaturation of SiO2--up to factors of 100,0000--which the authors propose nucleates by forming grains of less than 100 nanometers in diameter. Silica deposition occurs through a succession of metastable polymorphs including hydrated silica. These phases evolve during the pressure recovery around the initial cavity. The authors propose, but do not develop quantitatively, that these large drops in fluid pressure cause a complicated "cascade of coupled, nonlinear chemical responses" that result in the complex assemblages that are found in veins. Precious metal solubilities depend strongly on pressure.
Isolated slips do not deposit huge amounts of gold, but rather result in the deposition of only a thin coating of silica-gold vein material. The mass of this material is increased during the recovery stage. The authors suggest that it takes tens of thousands of years, but less than 100,000 years to form a high-grade deposit.
*Weatherley, D.K. and Henley, R.W., "Flash vaporization during earthquakes evidenced by gold deposits," Nature Geoscience, online March 17, 2013, DOI: 10.1038/NGE01759.