Dynamics of phase fronts in magmagenic fluid in the formation of gold and silver deposits in Southern Kamchatka

The origin of gold and silver deposits in the Southern Kamchatka ore district is considered in terms of a quantitative model of the dynamics of volcanogenic orthomagmatic fluid systems (VOFSs). This model takes into account structural, fluid dynamic, and thermophysical features of phase evolution in hydrothermal fluid systems differing in geometry and structural conditions of the discharge on the surfaces of volcanic edifices. It is shown that VOFSs forming sulfide-rich gold and silver deposits have no stationary impermeable caps in their discharge areas. Rather, for the most part, narrow regions of junction of phase fronts form in their interiors and migrate to the surface of volcanic edifices.Three geothermal system types are predicted by the example of plane and conical fluid conductance zones with a cap horizon: (I) where the shallow decompression boiling zone does not arise at all because of large lateral heat loss, (II) where subsurface decompression boiling zones appear at the beginning of the heat wave formation and then such a zone is practically confined to the cap rocks, and (III) where a quasistationary decompression boiling zone forms after an initial instability period or approach to a thermal equilibrium. Fluctuations or oscillations of decompression boiling zone fronts within a range of depths can exist in type III systems..