To help interpret spectral induced polarization (SIP) data collected in the field on waste piles<br>from sulfide mineral-bearing mines in Colorado and New Mexico, the piles were extensively sampled<br>and the SIP properties of the samples were measured in the laboratory. The laboratory spectra were fit<br>using 2-term Cole-Cole relaxations. Simple IP indices which can readily be compared with field data<br>were also defined and calculated from the laboratory results.<br>Samples containing unaltered sulfide minerals had strong relaxation features in the frequency<br>range from about 0.01-100 Hz. These relaxation features consist of resistivity values that start out low<br>and that continue to drop with increasing frequency, and phase values that are generally negative and<br>large and whose curves are concave down, over that frequency range. In most western U.S. mine waste<br>piles, however, the original sulfide minerals have been weathered and chemically altered to an extent,<br>changing to sulfate and oxide minerals such as jarosite, anglesite, and goethite. As this happens the<br>sulfide relaxation features on the corresponding spectra fade and disappear. The resistivity curves rise<br>and flatten over that frequency range, whereas the phase curves drop in absolute value and flatten or<br>even become concave up.<br>As water is added to dried samples, they become more conductive and their spectra change<br>markedly, typically changing from spectra like those of weathered mine waste to spectra that<br>superficially resemble those of material containing unaltered sulfide minerals.<br>Unfortunately, laboratory spectra generally fail to resemble spectra measured in the field. This<br>might be because of varying water content, or because of disturbances resulting from the sampling<br>process. We suspect, however, that inherent scaling factors are responsible for the differences between<br>spectra measured on cm-size laboratory samples and those measured on m-size field blocks.


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