Akademik Veri Yönetim Sistemi
ORE GEOLOGY REVIEWS, cilt.118, 2020 (SCI-Expanded)
The Biga Peninsula (NW Turkey) is an important sector of the Tethyan Metallogenic Belt. In addition to Au and Ag, this region hosts several Pb, Zn, Cu, Fe, and Mo deposits. Pb-Zn skarn mineralizations in the Biga Peninsula (Biga Pb-Zn skarn) are bounded by carbonate lenses in the metamorphic rocks and localized along the regional faults and at the contact between carbonate units and igneous-metamorphic rocks. The primary ore minerals are galena, sphalerite, chalcopyrite, pyrite, arsenopyrite, magnetite, and hematite. Ore-bearing altered rocks are composed primarily of talc-silicate alteration minerals, including both prograde (grossular-andradite garnets and johannsenite-hedenbergite pyroxenes) and retrograde (epidote, chlorite, quartz, and calcite) assemblages. The garnet composition is a solid solution with < 96% andradite and 1.4% to 94.4% grossular content. Some garnet grains exhibit zonings because of fluctuations in the content of Al3+ and Fe3+. Mn/Fe ratios are high, and the outermost grains have a high MnO content, up to 3 wt%. The pyralspite content is < 10 wt%. The proportions of johannsenite and hedenbergite in clinopyroxenes range from 0.35 to 94.69 mol% and 2.13 to 77.90 mol%, respectively. Clinopyroxenes have high Mn/Fe values, with Mn content up to 10 wt%. The epidotegroup minerals with a high Al3+ and Fe3+ content belong to the epidote-clinozoisite series (Ep(37-21)Czo(78.63)Pie(10)). Mineral chemistry data indicate that Biga Pb-Zn skarn deposits and distal Pb-Zn skarn deposits throughout the world have similar characteristics. The abundance of graphite in the metamorphic host rocks and the andradite-hedenbergite content of the skarns imply that the studied mineralizations were formed under reducing conditions. The ranges of crystallization depth and pressure values calculated from the chemistry of garnet-dinopyroxene pairs are 1.3-1.6 km and 10-12 MPa, respectively. Because these values are less than those of plutons hosting the Biga Pb-Zn skarn deposits, the mineralizations likely formed in the distal zones of plutons.