Document Type : Original Research Paper
Authors
1 Ph.D.Student, Department of Geology, Faculty of Basic Sciences, Islamic Azad University, Science and Research Branch, Tehran, Iran
2 Associate Professor, Department of Geology, Faculty of Basic Sciences, Islamic Azad University, North Tehran Branch, Tehran, Iran
3 Associate Professor, Department of Mining Engineering, Faculty of Engineering, Islamic Azad University, South Tehran Branch, Tehran, Iran
Abstract
The Khankeshi stratabound copper deposit is located in Markazi province, 80 Km SW of Tehran. The area is covered by a sequence of E-W trending lava flows and pyroclastic of Late Eocene age. The volcanic rocks can be classified as trachyandesite and andesite.The rocks contain a high fraction of potassium calc-alkaline and their geochemical characteristics attribute them to back arc basin and extentional processes. The oldest rocks of the study area are Elta unit , composed of green andesitic tuff located in south eastern of the khankeshi. This part indicates a basin with volcanic activities and exhalites, and green tuff with thin lamination combined with microcrystalline carbonates. On the other hand, presence of carbonate of micrite with framboidal pyrite in this part indicated reducing environment and Exhalites activity by source of sulfur in manto type mineralization in the khankeshi. The host rock is Elt type latite andesite with mega porphyritic texture and involved major ore chalcopyrite, bornite with pyrite and minor chalcocite, covellite, hematite, Goethite and malachite with dolomite and dolosparite veins. Framboidal pyrite is replaced with forms of fine and circle chalcopyrite and bornite in primary micritic background and subhedral crystals into dolosparite veins of crystallized micrititic carbonate micrite in forms of epigenetic that produce the supergene secondary production. This unit with pyroclastics and tuff breccias(Elta unit), indicated volcanic cycle that mineralization of copper, in forms of stratabound, has taken place in it. Local alteration associated with copper mineralization includes weak chloritization, oxidation with local argillic, serecitic and zeolitic. Mineralization is stratabound and copper mineralization occurs as disseminated, vein-veinlet,open space fillings and replacements. Based on fluid inclusion studies on coexisting calcite, Homogenization temperatures are between 129.4 to 227.1(with an average of 175°C).Salinity varies between 1.91 to 13.40(average 12) wt٪ NaCl eq. The depth of fluid inclusion trapping is estimated to be less than 200 meters and ore formation has occurred at pressure values less than 74 bars. Geological, ore mineralogy, ore texture, structures and fluid inclusions characteristics in the khankeshi deposit are similar to those reported from Manto type copper deposits.
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