Geology, mineralogy and the Pb, S isotope study of the Kalki{dotless}m Pb-Zn ± Cu deposits, Biga Peninsula, NW Turkey

Abstract

Three main Pb-Zn ± Cu deposits (Handeresi, Baǧi{dotless}rkaçdere, and Fi{dotless}ri{dotless}nci{dotless}kdere) occur south of Kalki{dotless}m in the southeastern part of the Biga Peninsula (NW Turkey). Massive and disseminated Pb-Zn mineralization consists of ore veins in fault zones and replacement bodies in carbonate layers in metamorphic rocks. Garnet (~Ad64Gr36), pyroxene (~Di30Hd45Jo25), epidote and rare tremolite-actinolite are found as gangue minerals in ore zones. The garnets often show oscillatory zoning and correspond to grossular, andradite and grandite in composition. The pyroxene minerals are manganiferous hedenbergite, johannsenite and diopside. The Mn/Fe ratios of the pyroxene range between 0.3 and 0.9 (mean 0.5). Such compositions of the garnet and pyroxene and gangue assemblages are typical of distal Pb-Zn skarns. The ore minerals are pyrite, sphalerite, chalcopyrite, galena, magnetite, hematite, and arsenopyrite. The mean lead isotopic values for galena are 206Pb/204Pb ~ 18.760, 207Pb/204Pb ~ 15.689, and 208Pb/204Pb ~ 38.935. The comparison of these isotope data with the host-rock samples (graphite schist, andesite and granodiorite) indicates that part of lead could have been leached from the schists. The δ34SVCDT values for galena, sphalerite, and chalcopyrite are -1.1 to +1.5 ‰ (mean: -0.2 ‰), 0.7 to +2. 1 ‰ (mean: +0.7 ‰), and -0.6 to +1.5 ‰ (mean: +0.4 ‰), respectively. Lead isotope data and δ34SVCDT values close to 0 ‰ indicate the formation of ores by magmatic processes. Taken together, the Oligo-Miocene magmatism in the area is taken responsible for the polymetallic mineralization. However, the metamorphic rocks and their protoliths may have contributed part of the lead.