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25 <br />0 <br />PHYSICAL FACTORS AFFECTING DRAINAGE QUALITY <br />This chapter discusses how other geologic and hydrologic <br />factors will change the weathering reactions. of the ore <br />minerals. Investigations within the Front Range of Colorado <br />have shown that at least three other parameters are important <br />for determining the chemistry of a drainage. These are the <br />ore petrology, the ground water hydrology and the physical <br />occurrence of the ore in the ground. Each of these will <br />be discussed. Much of what follows also occurs in two other <br />papers (11, 12). <br /> ORE PETROLOGY VS. WATER QUALITY <br /> In the Central City Mining District, the zones of minera- <br /> lization have been well established (4). These zones are <br /> shown in figure 2; and figure 3 shows the zonal distribution <br /> of the vein forming minerals. The central zone consists <br /> of pyrite veins and it is surrounded by a peripheral zone of <br /> galena-sphalerite veins. The intermediate zone, which con- <br /> tains most of the important mines, has transitional veins <br /> that consist of minerals characteristic of the other two <br /> zones. Wildeman and others (11) have found 8 abandoned <br /> adits which are continuously draining, 2 in the central zone, <br /> 3 in the intermediate zone, and 3 in the peripheral zone. <br /> The ranges in concentration of various elements for the <br /> drainages from each zone are listed in Table II, and these <br /> ranges highlight the zonal changes in the water chemistry. <br />M The most important conclusion that is shown by the zonal