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T-4518 9g <br />chalcopyrite (Fig. 35c). The coarser chalcopyrite blebs may be better explained as <br />codeposidonal with the host sphalerite (Bortnikov et al., 1991) or as exsolution features. <br />In the dusted texture, chalcopyrite replacement originates from a fracture, leaving behind a <br />zone of colorless sphalerite (Fig. 356). Bimodal texture is an intergrowth of highly <br />contrasting dark and light sphalerite (Fig. 35cQ. <br />Replacement began preferentially in iron-rich zones but because iron was <br />conserved in the process, those zones became depleted in iron. Advanced replacement, as <br />seen at the Cross, destroyed any original color/composirional banding (Bazton and 13ethke, <br />1987). Sixteen sphalerite grains were analyzed by microprobe to determine any difi'erence <br />in iron content between dazk and light sphalerite. Results aze given in Table 2: <br />Table 2. Iron content in sohalerite* <br />f <br />t <br /> Weigh[ % Fe Weight % Fe <br />of li ht s halerite of darks halerite <br /> 0.23 0.06 <br /> 0.23 0.07 <br /> 0.19 0.27 <br /> 0.13 0.12 <br /> 0.10 0.09 <br /> 0.13 0.08 <br /> 0.18 0.07 <br /> 0.03 0.08 <br />•n30L 1XA-8600 n 15 kV and 25 mA with a I Y+n dinmetu beam <br />end the following standards: pyrite fork, S; Zn (or 7n. <br />Iron content was low in al] analyzed sphalerite grains. Though the results azc: not <br />conclusive, light sphalerite may have a slightly higher iron content than dark sphalerite. It <br />is reasonable to conclude that the dark color of Goss sphalerite is due to abundant <br />chalcopyrite blebs. <br />Deposition of anhedral, fine- to medium-grained (typically 0.1 to 1 mm but a:. lazge <br />