Abstract

The phase equilibria in the system Pd–Pb–Te was studied by the evacuated-silica-tube method, electron-microprobe and X-ray powder-diffraction analyses. We investigated the 400°C isothermal section. The phase PdTe, the analogue of kotulskite, forms an extensive solid-solution and dissolves up to 30.2 at.% Pb; the phase Pd9Te4, the analogue of telluropalladinite, dissolve up to 2.3 at.% Pb, and the phase Pd20Te7 dissolves up to 5.5 at.% Pb. The phase Pd13Pb9 dissolves up to 2.1 at.% Te, and the phase Pd5Pb3, up to 7.7 at.% Te. Lead substitutes for tellurium. In the system Pd–Pb–Te, there are two ternary phases: Pd3Pb2Te2, the analogue of pašavaite, and Pd71Pb8Te21, not known to occur in nature. Pašavaite forms a stable association with kotulskite solid-solution in a compositional range from 25 to 30 at.% Pb and altaite. Phase Pd71Pb8Te21 forms a narrow solid-solution; its Pd content varies between 69.5 and 71.2 at.%, its Pb content, over the range 4.6 and 10.7, and its Te content, over the range 19.8 and 25.0 at.%. The phase Pd71Pb8Te21 forms stable assemblages with zvyagintsevite, telluropalladinitess, kotulskitess and Pd20Te7ss. Thus, such associations can be expected to occur in nature. Apart from the ternary phases, the binary phases PdPb2, PdPb, Pd13Pb9, Pd5Pb3, Pd3Te2, Pd20Te7, and Pd17Te4 can be expected to occur in nature in close association with other platinum-group minerals, in particular with known minerals of the system Pd–Pb–Te.

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