Genetic investigation and comparison of Kartalda? and Madenda? epithermal gold deposits in ?anakkale, NW Turkey

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• 作者：Ezgi Ü ; nal ?mer^a ; ^{e.unal@uq.edu.au} ; Nilgü ; n Gü ; leç ; ^a ; ^{nilgun@metu.edu.tr} ; ?lkay Ku?cu^b ; ^{ikuscu@mu.edu.tr} ; Anthony E. Fallick^c ; ^{T.Fallick@suerc.gla.ac.uk}
• 关键词：Kartalda? gold deposit ; Madenda? gold deposit ; Hydrothermal alteration ; Epithermal deposits ; Fluid inclusion ; Stable isotope ; NW Turkey
• 刊名：Ore Geology Reviews
• 出版年：2013
• 出版时间：September, 2013
• 年：2013
• 卷：53
• 期：Complete
• 页码：204-222
• 全文大小：5749 K

文摘

Two epithermal gold deposits (Kartalda? and Madenda?) 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 Kartalda? 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 ¡À 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 (¦Ä¹⁸O_(quartz): 7.93 to 8.95¡ë and calculated ¦Ä¹⁸O_(H2O): ? 7.95 to 1.49¡ë) and pyrite (¦Ä³⁴S_(pyrite): ? 4.8¡ë and calculated ¦Ä³⁴S_(H2S): ? 6.08 to ? 7.20¡ë) 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 ¡ãC, 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 ¡ãC.

The Madenda? deposit (0.27-20.60 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 (¦Ä¹⁸O_(quartz): 9.55 to 18.19¡ë and calculated ¦Ä¹⁸O_(H2O): ? 2.97 to 5.54¡ë) suggest varying proportions of meteoric and magmatic sources for the ore bearing fluid, sulfur isotope ratios (¦Ä³⁴S_(pyrite): ? 2.2¡ë and calculated ¦Ä³⁴S_(H2S): (? 3.63) to (? 3.75) ¡ë) 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 ¡ãC 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 Kartalda?. On the other hand, Madenda? 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 Kartalda? and Madenda? deposits, the similar temperature and salinity ranges obtained from their fluid inclusions, and the similar ages of igneous rocks in both deposits (Kartalda?: 40.80 ¡À 0.36 to 42.19 ¡À 0.45 Ma, Madenda?: 43.34 ¡À 0.85 Ma) the mineralizing systems in both deposits are considered to be genetically related.