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29 <br />• <br />the base metals and in the case of Na and K there appears to <br />be no variation. The concentration ranges of the major <br />metals in ground water samples taken from the Central City <br />District show the same tight spread. It was found that <br />these concentrations of Na, K, Mg, and Ca correlate well <br />with the abundances of these elements in the wall rocks which <br />are normally found along faults and veins in the Central <br />City District (3). This suggests the relative amounts of <br />these major metals in the water is a reflection of the compo- <br />sition of the more important rock units in the mining dis- <br />trict and the way in which these rocks weather. <br />In summary, they are two sources for the chemical con- <br />stituents in a mine effluent. The base metals and S04 <br />are derived from the vein minerals and the abundance of py- <br />rite in the veins is important in controlling the levels of <br />these metals in the mine effluent. The source of the major <br />metals is the wall rock and the composition of the host rock <br />determines the abundances of these constituents in the mine <br />drainage. <br />GROUND WATER HYDROLOGY VS. WATER QUALITY <br />Describing the mechanisms for ground water recharge <br />can become quite complex and relating this to water chemistry <br />adds another dimension to the difficulty. However, studies <br />in Pennsylvania on the water chemistry of springs issuing <br />from carbonate terrains have generated two simple models <br />for ground water systems and these can be treated as end <br />members for all recharge systems (28, 29). The two aquifer