Can two fluids of differing densities mix in porous media?

FranĀ Asks PERM: Hello, I've been out of school for 40 years but once thought I knew a lot about MVTs (Mississippi Valley Type Lead/Zinc Deposits). We operated under a hypothesis that two fluids were involved: a metalliferous basinal brine and a sulphurous trap in a dolostone 'reef'. However we were constrained to believe that two [...]