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Kahang |
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Iran |
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Cu Mo Au
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Super Porphyry Cu and Au
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The Kahang porphyry copper (-molybdenum-gold) deposit is located in central Iran, ~73 km ENE of Isfahan and 320 km SSE of Tehran.
This deposit occurs in the Saveh-Yazd Porphyry Copper Belt, the central part of the 2000 x 150 km Cenozoic Urumieh-Dokhtar magmatic belt, which extends across Iran from the NW - SE, and has been interpreted to represent an Andean-type magmatic arc related to subduction active from the late Jurassic to the present. It is composed of voluminous tholeiitic, calc-alkaline and K-rich alkaline intrusive and extrusive rocks, with associated pyroclastic and volcanoclastic successions along the active margin of the Iranian plates. This belt hosts the main Iranian porphyry deposits of Iran, including Sarcheshmeh, Sungun, Meiduk and Darehzar. For detail of the setting see the Iranian Porphyry Copper and Epithermal Gold Province which includes links to descriptions of the deposits listed above
The principal lithologies at the Kahang deposit comprise Eocene volcanic-pyroclastic rocks, intruded by a composite stock of Oligocene to Miocene porphyritic granitoids which have quartz monzonite, monzodiorite-monzogranite to dioritic compositions. The Eocene country rocks consist of andesite, trachyte, trachy-andesite, silicic breccias lava and tuffs. The principal geologic structures are a NW-SE and NE-SW trending fault systems (Harati et al., 2013).
The magmatic events of the Kahang area have been interpreted as follows (Harati et al., 2013):
i). Explosive eruptions of pyroclastics such as tuff and tuff breccia;
ii). Flows of andesitic to dacitic lavas with porphyritic textures from the volcanic edifice, comprising periodically repeated eruptions of pyroclastic rocks and lavas;
iii). Emplacement of sub-volcanics and intrusive rocks with dacitic, andesitic, monzonitic and dioritic compositions.
The Kahang host intrusions are characterised by enrichments in large ion lithophile elements (LILE) and depletions in high field strength elements (HFSE), and display features typical of subduction related calc-alkaline magmas (Haroni and Veiskarami, 2017).
Mineralisation at Kahang is mainly hosted by Eocene sub-volcanic rocks, especially porphyric quartz diorites, monzodiorite-monzogranite and dacitic rocks. The dominant ore minerals are chalcopyrite, pyrite and bornite with lesser chalcocite, covelite and malachite, and less abundant disseminated chalcocite, covelite, chalcopyrite, malachite and native gold that have accumulated in silicic veins and veinlets. Native Au particles are found in chalcopyrite in the eastern part of the deposit, whilst hematite, magnetite, goethite and jarosite have been identified in the oxidised zone (Harati et al., 2013).
Hydrothermal alteration is pervasive, covering in an area of >10 km2. Detailed mapping has outlined the usual four main hydrothermal alteration types (Harati et al., 2013):
i). Potassic, which is located in the central part of the deposit, occurring as a secondary biotite-K feldspar-magnetite veinlet assemblage
accompanied by chalcopyrite and pyrite mineralisation;
ii). Phyllic, mostly restricted to the eastern part of the deposit, were it comprises strong quartz, sericite and albite development within an argillic matrix. This quartz-sericite alteration is extensively developed within acidic to intermediate sub-volcanic domes.
iii). Argillic, which occurs in the eastern part of the deposit and consists of an extensive intermediate to strong alunite bearing zone that represents a silicified epithermal system superimposed on the upper most parts of the deposit.
iv). Propylitic, which marks the peripheral portions of the stock and hydrothermal system, and is dominated by chlorite, epidote and albite.
The deposit has estimated resources of:
>60 Mt @ an average grade of 0.6% Cu, 70 ppm Mo (Tabatabaei and Asadi Haroni, 2006),
Proved reserve - 40 Mt @ 0.53% Cu, 0.02% Mo plus an estimated reserve of 120 Mt at an unstated grade (Komeili et al., 2017 after Asadi 2007).
The most recent source geological information used to prepare this decription was dated: 2017.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
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Selected References:
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Afshooni, S.Z., Mirnejad, H., Esmaeily, D. and Haroni, H.A., 2013 - Mineral chemistry of hydrothermal biotite from the Kahang porphyry copper deposit (NE Isfahan), Central Province of Iran: in Ore Geology Reviews v.54, pp. 214-232.
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Barak, S., Bahroudi, A. and Jozanikohan, G., 2017 - Exploration of Kahang porphyry copper deposit using advanced integration of geological, remote sensing, geochemical, and magnetics data: in Journal of Mining and Environment, v.17, 22p. DOI: 10.22044/jme.2017.5419.1357
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Harati, H., Khakzad, A., Omran, N.R., Afzal, P., Hosseini, M. and Harati, S., 2013 - Identifying Hydrothermal Alteration: Geochemical Particulars based on Lithogeochemical Data from the Kahang Cu Porphyry Deposit, Central Iran: in Iranian Journal of Earth Sciences, v.5, pp. 1-12,
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Komeili, S.S., Khalili, M., Haroni, H.A., Bagheri, H. and Ayati, F., 2017 - The nature of hydrothermal fluids in the Kahang porphyry copper deposit (Northeast of Isfahan) based on mineralography, fluid inclusion and stable isotopic data: in Journal of Economic Geology, (In Farsi, with English Abstract) v.8, 23p. DOI: 10.22067/econg.v8i2.37178.
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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