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<br />The close correlation between the waters and the meteoric water line indicates minimal <br />exchange of oxygen isotopes between waters and rocks. (It takes a relatively large ~ock:water <br />ratio for water-oxygen to exchange with rock-oxygen; this can be accomplished if a considerable <br />amount of contact occurs between each parcel of water and a large volume of rock, a process that <br />can be acquired through deep crustal circulation over a long period of time.) This points to a <br />relatively young age for the waters, although young in this case might be thousands of years as <br />opposed to tens of thousands. Overall, the values argue for relatively rapid recharge of the <br />groundwater (thousands of years). Nevertheless, there is good evidence that some of the fault <br />waters, notably a few from the Southeast Head gate fault and the B East Mains fault, have <br />undergone some water:rock exchange prior to discharge in the underground mine. <br />Variable mixtures of local meteoric water and fault water can readily explain the range of <br />SD and 5180 values in all of the waters. The SD and 5180 values of the NW panels sump and the <br />Edwards mine portal are identico! within analytical uncertainty. One might expect some shift <br />along the meteoric water line due to local meteoric water vaziations with season, but [he virtually <br />identical nature of these two samples in context of the physical circumstances supports the notion <br />that they represent a mixture containing meteoric water that is not only very local, but also <br />probably derived from snow or rainfall that fell in the same season of the yeaz. <br />Insofar as the NW Panels sump water may represent the Edwards Portal seep water, it is <br />clear that meteoric water mixing has occurred within or prior to reaching the sump. And <br />although other constituents require it, no further mixing is needed to explain the seep water <br />composition, at least in terms of SD and 5180 values. <br />S"C. There is a significant shift in S"C values between the fault waters and the seep water. <br />(The value of +24, which was reported for the B-seam sample, is probably a misprint; that value <br />is more likely -24 or perhaps +2.4 or -2.4 %o. This could significantly affect other <br />interpretations. Generally, this analysis was disregazded.) Fault waters are significantly heavier <br />(range = -2.7. to +10.7 %o) than the seep water (-12.9 %o). Several mechanisms might produce <br />such a shift. <br />Interactions with meteoric water can be called on to explain part of a shifr from the heave <br />S"C fault waters to the light seep waters, because atmospheric CO, has a lighter S"C (about -7 <br />per mil). However, this obviously cannot account for all of the shift. Soil gas CO,, which is <br />considerably lighter (range = -] 0 to -30 %o -- see values in P. Defines, "The Isotopic Composition <br />of Reduced Organic Cazbon" in P. Fritz and J.Ch.Fontes, 1980, Handbook of Environmental <br />Isotope Geochemistry, Elsevier, p. 329-434) could account for all of the shift to lighter values, <br />provided enough soil water was encountered. <br />A single "Barren member" sample, which has a S''C value of -9.3 %o, and which is very <br />close in composition to the seep waters, can also help explain part of the shift to lighter values, <br />but not all of the shift, assuming this value is representative of the unit as a whole. (Variation in <br />B-seam S''C values would be useful to know as would variations in the sump waters.) If the <br />single B-seam value, which was reported at +24 4ou, were actually -24 %o, there would very little <br />need to call on high amounts of light carbon from soil gases or other sources. <br />8 <br />