Geological, geochemical and microthermometric characteristics of the Hakkari region Zn-Pb deposits, SE Turkey

The Hakkari region in SE Turkey contains large Zn-Pb deposits, primarily of non-sulfide ore in Upper Triassic passive margin carbonates. In the Karakaya, Meskantepe and Uzilmcil Zn-Pb deposit, the 3 main and > 15 ore layers alternate with a thick-bedded limestone. The feeder in the region veins are well defined, containing both non-sulfide and sulfide ore. Primary sulfide ore contains between 1 and 37 % Zn, has transformed to "non-sulfide" ore containing Zn > 10%. Both non-sulfide and sulfide ore is associated with As, Se, Hg, Tl, Mn and Sb, which is similar to other SEDEX deposits. The average delta(34)5 of the stratiform and feeder zone sulfides are 2.1 parts per thousand and 1.67 parts per thousand, respectively. Sulfur isotope data of sphalerite, galena and pyrite (from - 3.4 to 8.8 parts per thousand) indicates that sulfur came from a homogeneous large source. Sulfate was reduced by the process of thermochemical sulfate reduction (TSR) rather than bacterial sulfate reduction (BSR). Lead isotope values ((206)pb/(204)pb approximate to 18.49, (207)pb/(204)bp approximate to 15.66 and (208)bp/(204)bp approximate to 38.69) reflect an evolved upper crustal source. The homogenisation temperature (T-h) and salinity of fluid inclusions is from 165 to 289 degrees C, and from 1 to 22% equiv. NaCl salinity. Such a wide range of T-h and salinity, and Cl/Br ratio (409 from sphalerite and galena; 662 from barite) of fluid inclusions may indicate mixing of basinal brines and seawater. Successive ore levels, laminated with shale-carbonate rich in organic matter, formed on the seafloor as banded and replacement ore. Trace element associations, fluid inclusion and isotope data indicate that the Zn-Pb deposits were formed as synsedimentary processes associated with feeder systems during the initiation of the Triassic rifting as a vent-proximal SEDEX-type. The metals (Pb, Zn, Fe) were leached from Palaeozoic and older clastic rocks in the Arabian platform by seawater sourced fluids, and ascended through deep fractures. The metalliferous fluids should have formed vein type mineralization in feeder zone, sub-seafloor replacement type ore under the ocean floor, and stratiform ore on the seafloor.