Mineral assemblages,fluid evolution,and genesis of polymetallic epithermal veins,Glojeh district,NW Iran |
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| Institution: | 1. Department of Geochemistry, Faculty of Earth Sciences, Kharazmi University, Tehran, Iran;2. United States Geological Survey, Box 25046, MS 973, Denver Federal Center, Denver, CO 80225, USA;3. Mining Department, Faculty of Engineering, University of Kurdistan, Sanandaj, Iran;4. Geological Survey of Norway (NGU), Leiv Eirikssons vei 39, 7491 Trondheim, Norway;1. Faculty of Natural Resources and Earth Sciences, Shahrekord University, Shahrekord, Iran;2. Department of Mining, Faculty of Engineering, University of Kurdistan, Sanandaj, Iran;3. Department of Earth and Environmental Sciences, Graduate School of Environmental Studies, Nagoya University, Nagoya 464-8601, Japan;4. Department of Geography and Geology, University of Salzburg, Salzburg, Austria;5. State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi''an 710069, China;1. Department of Economic Geology, Tarbiat Modares University, Tehran, Iran;2. Dept. d''Enginyeria Minera, Industrial i TIC, Universitat Politècnica de Catalunya, Barcelona, Spain |
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| Abstract: | The Glojeh district contains silver- and base metal-rich epithermal veins and is one of the most highly mineralized locations in the Tarom-Hashtjin metallogenic province, northwestern Iran. It consists of four major epithermal veins, which are located in the South Glojeh and North Glojeh areas. Alteration in the Glojeh district consists of propylitic, sericitic, and argillic assemblages, as well as extensive silicification. The ore-bearing veins comprise three paragenetic stages: (1) early Cu-Au-As-Sb-Fe-bearing minerals, (2) middle stage Pb-Zn-Cu-Cd-Ag-bearing minerals, and (3) late hematite-Ag-Bi-Au-Pb mineralogy. The veins are best classified as the product of an early high-sulfidation hydrothermal system, which was overprinted by an intermediate sulfidation system that was rich in Ag and base metals. Hematite is locally altered to goethite in zones of as much as 40 m in width during supergene alteration and the goethite is an important exploration tool. Fluid inclusions from the early, middle, and late stages, respectively, have salinities and homogenizations temperatures ranging from 5 to 11 wt.% NaCl eq. and 220 °C to 340 °C, to 1 to 8 wt.% NaCl eq. and 200 °C to 290 °C and finally to. 0.1 to 2 wt.% NaCl eq. and 150 °C to 200 °C. The oxygen isotope values in quartz range from 8.8 to 13.3‰ and most calculated fluid δ18O values are between 4 and 8‰, suggesting a magmatic fluid with some meteoric water contamination. Sulfur isotope values for chalcopyrite, pyrite, sphalerite, and galena are mainly − 7.3 to + 1.3‰ and − 0.3 to + 8.4‰ for North Glojeh and South Glojeh, respectively. Sulfur isotope data suggest a magmatic origin. Boiling, isothermal mixing, and dilution are the main mechanisms for ore deposition in the Glojeh veins. Recent 40Ar/39Ar age measurements of 42.20 ± 0.34 Ma and 42.56 ± 1.47 Ma for the North Glojeh and South Glojeh veins, respectively, overlap with the 41.87 ± 1.58 Ma age of the Goljin intrusion in the northern part of the district, which we interpret as the main heat source controlling the hydrothermal systems. |
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