Exploratory studies on substitutions in the tetrahedrite-tennantite solid solution series Part III. The solubility of bismuth in tetrahedrite-tennantite containing iron and zinc
Klü nder, Maiken Hansen; Karup-Mø ller, Sven; Makovicky, Emil
published: Apr 11, 2003
Bismuth-bearing tetrahedrite and tennanite were synthesized from dry runs in evacuated silica glass tubes at 350 °C, 450 °C and 520 °C, and studied by means of microprobe analyses on polished sections and X-ray powder diffraction. Charges were prepared with two Zn or Fe atoms p.f.u., with pure As, resp. Sb, or with As:Sb = 1:1. They were prepared with one and two atoms of Bi p.f.u., respectively, at all three temperatures. Separate sets of non-stoichiometric compositions were prepared in order to examine the influence of high- and low sulfur fugacity, respectively, on the solubility of Bi in tetrahedrite/tennantite. Our studies suggest that the solubility of Bi in tetrahedrite-tennanite is 0.8 atom p.f.u. at 350 °C and 1 atom p.f.u. at 450 °C and 520 °C, independent of the Sb/As ratio. It increases with the increase in S fugacity and vice versa. The average increment of the cubic lattice parameter a is 0.011Å/l Bi atom p.f.u. for tetrahedrite, that for tennantite is 0.036Å/l Bi atom p.f.u. in the range investigated. The most prominent associated phases studied were Bi-bearing bornite, cuprobismutite, Phase Z, and wittichenite.