Original paper
Exsolution mechanism of chalcopyrite from bornite solid solution
Hoshino, Kenichi; Watanabe, Makoto
Neues Jahrbuch für Mineralogie - Monatshefte Jg. 1997 Heft 4 (1997), p. 145 - 154
13 references
published: Jun 6, 1997
DOI: 10.1127/njmm/1997/1997/145
ArtNo. ESP156199704000, Price: 29.00 €
Abstract
The stoichiometric bornite composition must lie in the bornite solid solution field, in order for chalcopyrite to exsolve from the solid solution and for the compositions of chalcopyrite and bornite to be stoichiometric. However, the solid solution field recently studied indicates that the available amount of chalcopyrite exsolution is only a minor. Consequently, naturally observable amounts of chalcopyrite up to about 26 vol.% as in the bornite from the New Imperial mine, B. C., Canada, can no longer be explained by exsolution from the bornite solid solution without changing its bulk composition. By means of modal analyses and available phase diagram for the Cu-Fe-S system, the present investigation has made it possible to illustrate a mechanism of chalcopyrite exsolution from the bornite solid solution by an addition of sulfur. Depending on the amounts of Cu and Fe present, temperature, and/or other factor (s), sulfur is added to the system so that the bornite solid solution can eventually reach the stoichiometric composition. Because of this dependency, sulfur must be treated as a mobile component. It is calculated that exsolution can produce chalcopyrite up to 23 vol.% at 350°C. In conclusion, the majority of crystallographic intergrowth and possibly of other types of "exsolution textures" such as dot exhibited by bornite and chalcopyrite can be originated from exsolution during cooling.
Keywords
Exsolution mechanism • chalcopyrite • bornite solid solution • stoichiometric composition