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    Genesis of Tertiary Akcakis,la vein-type Pb-Zn-Cu mineralisation (Central Anatolia, Turkey): Evidence from fluid inclusion and O, H, S, Pb-isotope compositions
    (Pergamon-Elsevier Science Ltd, 2023) Unal-Cakir, Esra; Gokce, Ahmet; Harris, Chris
    The Akcakis,la Pb-Zn-Cu vein type deposit is one of the active mining deposits located in the Akdagmadeni (Yozgat) metallogenic province in Turkey. The sulfide vein deposit, trending E-W, is hosted by calcschist of the Akcakis,la and Topaktas, formations of Akdagmadeni metamorphites, which are intruded by the Central Anatolian granitoids and overlain by sedimentary and Tertiary volcanic rocks. Microthermometric measurements indicate that the Pb-Zn-Cu deposit formed by hydrothermal fluids containing dissolved CaCl2, MgCl2 and NaCl. A mixing of fluids with greatly varying salinities and temperatures is shown by the wide range of calculated salinity (0.2-10.4%) and temperature (170-400 degrees C) values. Isotope ratios of oxygen (& delta;18OH2O =-5.09 to +4.71%o) and hydrogen (& delta;D =-67%o and-82%o) suggest that water in hydrothermal fluid might be either mixing of meteoric and magmatic waters or meteoric water that oxygen isotope composition was modified by fluid-rock interaction. Sulphide minerals exhibit & delta;34S values ranging from 5.51%o to 8.40%o, which assume a magmatic sulphur source modified by assimilation of upper crustal material (possibly the host metamorphites). In galena from the studied Akcakis,la Pb-Zn-Cu deposit ratios of 206Pb/204Pb (18.783-18.821),207Pb/204Pb (15.654-15.700) and 208Pb/204Pb (38.874-39.039) suggest a mixture of lead sources from orogenic-upper crust materials. We assume that hydrothermal fluids dissolved the sulphur from the intruded granitoids and the lead from the host metamorphites. The galena Pb model ages values point out two different ore forming ages; suggesting initial formation in upper Cretaceous (87 Ma) and highly reworking in Eocene-Oligocene (23 and 39 Ma).
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    Microthermometric and O- and H-isotope characteristics of the mineralizing fluid in the Akguney copper-lead-zinc deposit, NE Turkey
    (TAYLOR & FRANCIS INC, 2009) Unal, Esra; Gokce, Ahmet; Harris, Chris
    The Akguney copper-lead-zinc deposit (Ordu Province) is actively mined in the eastern Black Sea Region of Turkey. This deposit consists of ore-bearing veins emplaced along fault zones and hosted by slightly altered Upper Cretaceous andesites. Seven ore veins, D-1 to D-7, have been identified. These veins strike N 70-80W with a dip of 50-60NE, except for D7 which strikes E-W with a dip of 25S. The ore-bearing quartz vein outcrops are slightly limonitized and hematitized. Two different ore associations are distinguished within the D-1 and D-2 veins. The first contains only pyrite, whereas the second consists of coarse-grained sulphides such as chalcopyrite, galena, sphalerite, tetrahedrite, and secondary limonite veinlets in addition to pyrite. Quartz and calcite are the gangue minerals. The mineral paragenesis has been identified as: pyritegalenachalcopyrite (I)sphaleritechalcopyrite (II)(tetrahedrite ?)quartzcalcite. Fluid inclusion data indicate that the ore-forming fluids contained significant concentrations of divalent cations in addition to NaCl. The salinity of the fluids lies in the range 14-24% (ave.=19.0) NaCl equivalent; liquid homogenization temperatures range from 276 to 349C (ave.=307C) and decrease to 211C through the later stages of mineralization. Oxygen and hydrogen isotope data are consistent with the mineralizing fluid being of meteoric origin, with modification of the oxygen isotope composition by exchange with the volcanic host rocks. However, low D values suggest a magmatic water component in some samples. The combination of fluid inclusion and stable isotope data suggest that the Akguney Cu-Pb-Zn vein-type deposits were formed by the leaching of metals and sulphur from the surrounding volcano-sedimentary rocks by deep-circulating meteoric water.