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The statement is made that the Edwards Portal spring water could not be "in-mine fault water" <br />because no plausible mechanism exists for reducing the Na content of water between the in-mine <br />faults and the Edwards Portal spring because the reduction in Na would require reverse ion <br />exchange. That ignores the equilibrium constant of the reaction, mathematically described by the <br />Gibbs Free Energy G in the following equation: <br />~G.~~=-RTInKa <br />where the driving force of the reaction (G) is a function of temperature and the equilibrium <br />constant KQ of the reaction. Using the 4th mineral reaction listed above, in which Mg is <br />exchanged for Na in a clay, <br />Mg ~ +Na -clay =2.Na ' +Mg -clay <br />the equilibrium constant is the activity of the reaction products divided by that of the reactants. <br />Symbolically, <br />Ka -~ aNu~~(aAfgclay~~(aAfg~laNarluyl <br />The activity (a) is essentially the concentration of each of those reaction constituents (Na, Mg, <br />Na-clay and Mg-clay). The Ka term is a constant for the temperature, so the proportions of <br />each participant in the reaction adjusts itself to maintain equilibrium concentrations at the <br />temperature at which the reaction is occurring. That is, if the Na-concentration of the system in <br />which the reaction is going on is very high, the reaction is effectively "driven" to the lefr, taking <br />Na from solution and replacing Mg on the Mg-clay, thus removing Na from the water. So the <br />statement that it is rare for the reaction to "proceed from products to reactants" may be true, it is <br />only because the reaction normally takes place in water with lower Na ion concentration than the <br />water in this system. Theoretically, these reaction could, in fact, reduce the Na-content of the <br />water. <br />Carbon Isotope Composition <br />The cazbon isotope signature was the second line of reasoning was used as evidence that the <br />water issuing from the Edwazds Portal spring is geochemically distinct and not the same water <br />that was derived from the faults. The evidence is not unequivocal. A wide range of carbon <br />isotope compositions is displayed by the waters sampled. Expressed as the ratio of the carbon-13 <br />to cazbon-12 relative to a standard (written as ~'C as a per mil quantity), these S"C values range <br />from +10.7 to -2.7 in the fault waters, certainly not consistent from fault-to-fault. Water from the <br />Lone Pine Gulch seal and the Edwazds Portal spring shows lighter cazbon (S"C values of -5.4 <br />and -12.9 respectively) than any of the fault waters. <br />