The late-Archean lode-type gold deposits are widely believed to be results of seismic pumping of deep metamorphogenic auriferous fluid in multiple cycles through a ‘fault-valve’ type mechanism. A 2-D numerical model gives a quantitative picture of fluid pressure build up and fluid flow by solving coupled flow, continuity, and storage equations with temperature-dependent rock and fluid properties using the COMSOL Multiphysics software. However, operation of this mechanism to cause repetitive cycles of fluid flow does not seem sustainable. Further, disposition and permeability of the seismic lid has important implication to fluid pressure build-up along with the orientation of fault (gentle/steep dipping). While a heat flux in excess of the geothermal gradient may be necessary for building up of supralithostatic pressure, the same could be attained by a far field stress. Furthermore, such scenario of pressure build-up and fluid flow is attainable without a seismic lid, hence it may not be a mandatory component of such minerallizing systems. Our results further sufficiently indicate that high-angle faults are more favourable pathways for fluid flow than the gently dipping reverse faults, Therefore, alternate mechanisms other than the fault-valve, need to be examined to understand such mineralizing systems, where steep-dipping faults/shears are more common, for example, the Sigma and Hutti gold camps.
Bhuyan et al. (Sat,) studied this question.