Genetic investigation and comparison of Kartaldag and Madendag epithermal gold deposits in Canakkale, NW Turkey

Abstract

Two epithermal gold deposits (Kartaldag and Madendag) located in NW Turkey have been characterized through the detailed examinations involving geologic, mineralogical, fluid inclusion, stable isotope, whole-rock geochemistry, and geochronology data. The Kartaldag deposit (0.01-17.65 ppm Au), hosted by Eocene dacite porphyry, is associated with four main alteration types with characteristic assemblage of: i) chlorite/smectite-illite +/- kaolinite, ii) quartz-kaolinite, iii) quartz-alunite-pyrophyllite, iv) quartz-pyrite, the last being characterized by three distinct quartz generations comprising massive/vuggy (early), fine-medium grained, vug-lining (early), and banded, colloform, comb (late) textures. Observed sulfide minerals are pyrite, covellite, and sphalerite. Oxygen and sulfur isotope analyses, performed on quartz (delta O-18((quartz)): 7.93 to 8.95 parts per thousand and calculated delta O-18((H2O)): -7.95 to 1.4 parts per thousand) and pyrite (delta S-34((pyrite)): -4.8 parts per thousand and calculated delta S-34((H2S)): -6.08 to -7.20 parts per thousand) separates, suggest a meteoric water source for water in the hydrothermal fluid, and an igneous source for the sulfur dissolved in ore-related fluids. Microthermometric analyses of primary fluid inclusion assemblages performed on quartz (late quartz generation) yield temperatures (Th) dominantly in the range of 245-285 degrees C and generally low salinity values at 0 to 1.7 wt.% NaCl eq. Based on the quartz textures and the associated base metal concentrations, along with fluid inclusion petrography, the early vug-lining quartz is considered to have been associated with the mineralization possibly through a boiling and a late mixing process at >285 degrees C. The Madendag deposit (027-20.60 ppm Au), hosted by Paleozoic mica schists, is associated with two main alteration types: sericite-illite-kaolinite, and quartz-pyrite dominated by two distinct quartz generations i) early colloform, comb and banded quartz and ii) late quartz, forming the cement in hydrothermal breccia. Whereas oxygen isotope analyses of quartz (delta O-18((quartz)): 9.55 to 18.19 parts per thousand and calculated delta O-18((H2O)): -2.97 to 5.54 parts per thousand) suggest varying proportions of meteoric and magmatic sources for the ore bearing fluid, sulfur isotope ratios (delta S-34((pyrite)): -2.2 parts per thousand and calculated delta S-34((H2S)): (-3.63) to (-3.75) parts per thousand) point to an essentially magmatic source for sulfur with or without contribution from sedimentary sources. Microthermometric analysis carried out on primary fluid inclusion populations of a brecciated sample (early quartz), give a temperature (Th) range of 235-255 degrees C and 0.0 to 0.7 wt% NaCl eq. salinity. Based on the textural relationship, base metal and high gold contents, the ore precipitation stage is associated with late stage quartz formation via a possible boiling process. The presence of alunite, pyrophyllite and kaolinite, vuggy quartz and covellite suggest a high-sulfidation type of epithermal deposit for Kartaldag. On the other hand, Madendag is identified as an adularia-sericite type owing to the presence of significant sericite, neutral pH clays (mostly illite, chlorite/smectite, and kaolinite), low temperature quartz textures (e.g., colloform, comb, and banded quartz), and limited sulfide minerals. Given the geographical proximity of Kartaldag and Madendag deposits, the similar temperature and salinity ranges obtained from their fluid inclusions, and the similar ages of igneous rocks in both deposits (Kartaldag: 40.80 +/- 036 to 42.19 +/- 0.45 Ma, Madendag: 43.34 +/- 0.85 Ma) the mineralizing systems in both deposits are considered to be genetically related. (C) 2013 Elsevier B.V. All rights reserved.