ИСТИНА

The purpose of this work is to determine the possible range of concentration and chemical state of Au and PGE (Pt, Pd, Rh) in sphalerite (Zn,Fe)S, greenokite (CdS) and covellite (CuS). The crystals of ZnS and CdS were synthesized using the gas transport method at 850°C and the salt flux one using NaCl/KCl, CsCl/NaCl/KCl, and LiCl/RbCl eutectic mixtures at 850, 645 and 470°, respectively. CuS were grown using the salt flux method in RbCl/LiCl melt at 470 and 340°C. The trace metal activity was always controlled by the presence of pure metal, and, therefore, the concentration (CAu, ppm) of these elements in synthesized phases represent the maximum possible value for given T/f(S2) synthesis parameters. In ZnS, synthesized at 850°C with admixtures of Cd, Se, In, Fe, and Mn, CAu reached 3000 ppm, whereas the cell parameter extremely increased up to 5.4161Å relatively to 5.4060 Å for pure ZnS. The observed high CAu is caused by the presence of In (2091±46ppm in (Zn,Fe,In)S in comparison with 14±7 in Zn(S,Se); 94±12 in (Zn,Fe,Mn)S; and 96±46 ppm in (Zn,Fe)S). The CAu in (Zn,Fe)S synthesized at 645°C <5 ppm; at 470°C <1 ppm. Therefore, increase of temperature results in the increase of CAu in ZnS. CAu in another (Fe,Zn)S series synthesized using gas transport method various from 200 to 500 ppm and depends on the iron content. This fact could be related to the oxidation state or Fe in ZnS-FeS solid solution series. The concentration of Pt, Pd, Rh in ZnS and CuS are below the LOD of LA-ICP-MS (∼30 ppb). Maxumum CAu in CuS can be observed at 450° and is equal to 3100 ppm. Maximum concentration of Au=515 ppm can be found in CdS with admixture of Fe. The gold distribution in all phases are homogeneous. According to XANES data, atoms of Au in the crystal structure of covellite is in triangles, formed by the atoms of Cu. In sphalerite gold is in "invisible" state too.