Abstract
Abstract The Gorevskoe Pb-Zn-Ag mine is currently the largest producer of Pb and Zn in Russia, exploiting one of the largest sediment-hosted Pb-Zn deposits worldwide. Despite its size and economic importance, the Gorevskoe deposit remains poorly understood. It is located on the western margin of the Siberian craton within the Yenisei Ridge, a Neoproterozoic orogenic belt. Mineralization consists of three tabular orebodies that are in turn composed of multiple stacked stratiform to strata-bound lenses of galena-pyrrhotite-sphalerite-rich massive sulfide ore, hosted in organic-rich marine metalimestones and calcareous slates of Stenian to Tonian age (1,020 ± 70 Ma). Extensive Fe-Mg-Mn-carbonate alteration haloes surround the ore lenses. The Pb isotope signature of the deposit is consistent with derivation of Pb, and probably all associated metals, from an evolved crustal source at the time of formation of the host rocks. The sulfur isotope compositions of pyrrhotite, sphalerite, galena, arsenopyrite, and pyrite (δ34S = 16.0–20.4‰) do not vary considerably across the deposit and are within the range reported for contemporaneous seawater, indicating complete reduction of marine sulfate as the main source of sulfur. The available geologic and geochemical data indicate that the Gorevskoe deposit belongs to the sediment-hosted massive sulfide (SHMS) class of Zn-Pb deposits, with an affinity to Selwyn-type deposits. Hydrothermal mineralization appears to be temporally related to rifting and distal mafic volcanism in a passive margin setting. Geologic relationships suggest that the orebodies formed in a diagenetic environment. Furthermore, the predominance of primary pyrrhotite over pyrite as the major iron sulfide, the presence of abundant siderite, and the relatively homogeneous sulfur isotope signature of the ores indicate highly reducing conditions during ore formation. They also constrain the character of the metal-bearing fluid to be similarly reducing, and of moderate temperature (200°–300°C). Gorevskoe may thus be regarded as one of the world’s largest Selwyn-type SHMS deposits.
Highlights
With pre-mining reserves and resources of 106.43 million metric tons (Mt) of ore at 6.14% Pb, 1.82% Zn, and 49 g/t Ag (Makarov et al, 2014), the Gorevskoe deposit is one of the largest Pb-Zn-Ag deposits worldwide
Despite its size and economic importance, the Gorevskoe deposit remains poorly understood. It is located on the western margin of the Siberian craton within the Yenisei Ridge, a Neoproterozoic orogenic belt
Mineralization consists of three tabular orebodies that are in turn composed of multiple stacked stratiform to strata-bound lenses of galena-pyrrhotite-sphalerite-rich massive sulfide ore, hosted in organic-rich marine metalimestones and calcareous slates of Stenian to Tonian age (1,020 ± 70 Ma)
Summary
With pre-mining reserves and resources of 106.43 million metric tons (Mt) of ore at 6.14% Pb, 1.82% Zn, and 49 g/t Ag (Makarov et al, 2014), the Gorevskoe deposit is one of the largest Pb-Zn-Ag deposits worldwide. Magnetite is rare in the Main and Western orebodies, except for isolated occurrences as disseminated grains and aggregates which are mostly related to the alteration haloes of some dolerite dikes (Makarov et al, 2014) and the metamorphic overprint (Kuznetsov et al, 1990) It is, more abundant in the Northwestern orebody, where it commonly occurs together with siderite and pyrite (in addition to pyrrhotite), and rarely forms separate quartz-magnetite-pyrite ± pyrrhotite ± siderite horizons (Kuznetsov et al, 1990; Ponomarev et al, 1991a; Makarov et al, 2014). This is unusual, since sphalerite is generally considered to be the most important host for this element in Pb-Zn ores (e.g., Bernstein, 1985; Frenzel et al, 2014)
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