Trace-elements in sulfides of the Dergamysh cobalt-bearing massive sulfide deposit, the Southern Urals: Mode of occurrence and matter sources

Subject of study. The article presents the results of study of trace elements (TEs) in sulfides of the main ore body (borehole 1T) and the northwestern ore body (borehole 200) of the Dergamysh cobalt-bearing massive sulfide deposit hosted in serpentinites (South Urals). Materials and methods. The chalcopyrite-pyrite-marcasite sandstones of the main ore body and pyrite-chalcopyrite-pyrrhotite “gravelites” of its northwestern satellite were studied with laser ablation with inductively coupled plasma. Results. The TE contents, distribution and mode of occurrence differ in sulfides of the main ore body and its northwestern satellite. In ores of the main ore body, most TEs (Ag, Sn, Mn, As, Co, Ni, Te, Pb, Au) accumulate in pyrite-1, pyrite-marcasite aggregates concentrate Tl and Bi, marcasite is a host to Mo and Sb, and chalcopyrite contains Zn, Se and Cd. Pyrite-2 is depleted in TEs relative to other sulfides. In sulfides of the northwestern satellite, most TEs are related to chalcopyrite (Bi, Te, Zn, Cd, Se, Pb, Au, Tl, Ni, Co). Tin accumulates in cubanite, As and Ni are hosted in pyrite-4, Ag, Mn and Mo are concentrated in pyrrhotite, Sb is typical of pyrite-3, and Co accumulates in pyrite-2. Conclusions. Based on the correlation analysis, it is shown that sulfides of the main ore body and its northwestern satellite are characterized by different mode of TE occurrences. The differences are explained by two main reasons: 1) “mafic” and “ultramafic” metal sources for sulfides of the main ore body and its northwestern satellite, respectively, and 2) different degree of diagenetic alteration of sulfides.