C. S. Spirakis
The role of semipermeable membranes in the formation of certain vanadium-uranium deposits
Economic Geology and the Bulletin of the Society of Economic Geologists (December 1977), 72(8):1442-1448

Abstract:
The Rifle-Garfield vanadium-uranium deposit, Garfield County, Colorado, is believed to have formed at an interface between a carbonate solution and a sulfate solution. Vanadium-silicate minerals in the ore appear to have acted as a semipermeable membrane which maintained the solution interface for a long enough time for the ore to develop. Selective diffusion through the membrane resulted in concentration gradients and pH changes on both sides of the growing ore deposit. Mineralogical zones of the deposit and alteration associated with the ore formed in response to the changes in the chemical conditions generated by the membrane.