Pseudomorphic hematite after ore clasts of gossanites of the Molodezhnoe Cu-Zn massive sulfide deposit (South Urals)

N.R. Ayupova, V.V. Maslennikov

UDK 553.435(470.5)

The structural and mineralogical features of pseudomorphic hematite after ore clasts are considered for gossanites (products of complete submarine oxidation of massive sulfde ores), which form the sedimentary halos at the fanks of the Molodezhnoe Cu-Zn massive sulfde deposit, South Urals. Submarine oxidation of Te-, Bi-, Pb-, Hg- and Ag-rich sulfde clasts was accompanied by the formation of pseudomorphic hematite with relict structural features. The most common fne-grained, reniform-collomorphic, framboidal and crystalline-grained (with growth zoning) pseudomorphs correspond to the clasts of hydrothermal crusts, fauna shells, outer zone and axial channel of smoker chimneys and pyrite crystalline aggregates with growth zoning. During oxidation, the trace elements were removed and precipitated in form of authigenic tellurides (tellurobismutite, tsumoite, hessite, volynskite, coloradoite), sulphotellurides (tetradymite) and Se-bearing galena in both pseudomorphs and quartz-chlorite-hematite matrix. The formation of tellurides in gossanites is caused by low Te mobility under oxidizing conditions of halmyrolysis-diagenesis due to its greater afnity with iron hydroxides.

Figs. 5. Table 1. Ref 32.

Key words: pseudomorphs, hematite, gossanites, submarine oxidation, massive sulfde deposits deposits, Urals

MINERALOGY № 4 2018