Morphology and grain size of chalcopyrite in intimate associations of sphalerite-chalcopyrite

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Morphology and grain size of chalcopyrite in the intimate associations of sphalerite-chalcopyrite including the chalcopyrite emulsion and "chalcopyrite disease" were carefully checked, based on microscopic observations of natural ores and on annealing experiments using synthetic Cu-Fe-bearing sphalerite solid solutions. Ore specimens from several Japanese deposits clearly show that chalcopyrite emulsions with larger grain sizes are included in Fe-rich sphalerite coexisting with pyrrhotite, and the emulsion texture is limited to relatively old deposits. The results of the annealing experiments for the Cu-Fe-bearing sphalerite samples synthesized at 800°C show that the habit of isocubanite or chalcopyrite as an exsolved phase is lamellar in Fe-rich sphalerite and lenslike to irregular bleblike in Fe-poor sphalerite, depending on FeS content of the host sphalerite. This feature would be applicable to sphalerite-chalcopyrite associations attributed to replacement reaction, because FeS in sphalerite is consumed to form isocubanite or chalcopyrite. Thus in the case of the sphaleritechalcopyrite associations by the diffusion-controlled growth, morphology and crystal size of chalcopyrite are controlled mainly by both FeS content of host sphalerite and kinetic effects.
資源地質学会の論文