Lead-zinc hydrothermal mineralization in the Pechenga Area, Kola Peninsula, Russia

Abstract

The Early Proterozoic Pechenga supracrustal belt in the western part of the Kola Peninsula, Russia contains hydrothermal Pb-Zn mineralizations, occurring as veins or sulphide disseminations along hydrothermally altered tectonic zones. These occurrences are confined mainly to the metasedimentary Productive Zone of the Pechenga supracrustal belt. Their lead isotopic compositions are similar to those Early Proterozoic mantle-derived mafic rocks, such as the gabbrowehrlite intrusion of the Pechenga Complex, that contain Cu-Ni sulphide ores. The lead-isotopic composition of the Pb-Zn mineralization is distinctly less radiogenic than that of base-metal veins from Archaean rocks bordering the Penchenga supracrustal belt. Fluid inclusions in quartz from the Pb-Zn mineralizations of Pechenga yield lower temperatures and higher CO2, contents than those in the hydrothermally mobilized Cu-Ni mineralizations. It is suggested that the hydrothermal solutions which produced the Pb-Zn mineralizations in the Pechenga area could be of Late Proterozoic - Early Palaeozoic age, and that metasedimentary rocks enriched in sedimentary iron-sulphides may have played the role of a 'geochemi- cal barrier', where dissolved metals were precipitated.