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Kisladag |
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Turkey |
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Au
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Super Porphyry Cu and Au
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The Kisladag porphyry gold deposit is located in Usak state of west-central Turkey between the major centres of Izmir, lying 180 kilometres to the west on the Aegean coast, and the capital city of Ankara, 350 kilometres to the northeast. It is also 35 km southwest of the city of Usak (#Location = 38° 30' N, 29° 12' E).
The deposit is located within a Miocene to Pliocene volcanic complex of the Anatolides belt of western Turkey which was related to a regional structural subduction zone along the Hellenic Trench lying to the southwest. In the Kisladag region, these volcanics were deposited onto a basement of schist on the northeastern margin of the uplifted Menderes Massif. The Kisladag gold deposit is located on the north-facing slope of the hill 'Gokgoz Tepe', within a prominent volcanic structure that forms part of a 90 km2 volcanic complex that trends NE-SW.
Within the deposit area, the main lithologies are generally pyroclastics which have been intruded latite porphyry. Intra-mineral breccias indicate that at least two, and possibly three, separate, compositionally and texturally similar mineralised intrusives are represented, consisting of a few percent of feldspar and hornblende phenocrysts in a fine grained latite matrix. A late, weakly mineralised to barren stock, marks the end of mineralising activity.
Gold mineralisation with traces of molybdenum, zinc, lead and copper encircles the late barren stock. Higher-grade gold mineralisation forms a horseshoe shaped annulus around the northern, southern and eastern sides of the late intrusive stock, and is associated with a multiphase quartz sulphide stockwork and pervasive silicification. The mineralised zones form and outward dipping a bell-shaped mass, subparallel to the contact of the stock.
Gold is associated with at least three phases of partially overlapping stockwork veining and brecciation, including i). intense quartz-tourmaline stockwork veining and quartz flooding of hydrothermal breccias; ii). multiple phases of quartz-pyrite veining containing gold and late sulphide-rich quartz veining with traces of molybdenum, sphalerite, galena and tetrahedrite; and iii). a final phase of vuggy barren silica veining is associated with intense acid leaching but is effectively barren of gold mineralisation. Outcrops of the late silicification form prominent vein and sill-like bodies away from the main deposit area and have been interpreted as eroded remnants of an original "lithocap".
The degree of stockwork veining generally decreases with depth, especially below the 650 metres (asl) elevation. Higher grade mineralisation (>2 g/t Au) has been drilled from surface to depths of >250 m below the surface. Lower-grade mineralisation of between 0.5 and 1.0 G/t Au, has been intersected to the deepest levels drilled of approximately 400 m below the surface.
The dominant sulphide encountered is pyrite with chalcopyrite, sphalerite, tetrahedrite, galena and molybdenite having been identified through microscopic studies. Traces of cinnabar and orpiment have also been observed in trench samples along with traces of scheelite, magnetite and rutile, as well as trace amounts of secondary chalcocite at or below the base of oxidation.
Oxidation is deeper on the uphill (southern) side of the deposit (to depths of from 30 m to 80 m) in contrast to the downhill (northern) side of the deposit where oxidation is only to from 20 to 50 metres below surface. Oxidation is slightly deeper to the the east (50 m to 100 m) versus the west side of the deposit where oxidation ranges from 30 to 60 m below the surface. Limonite is the most abundant oxide mineral, usually occurring in thin colloform layers along fractures and as disseminated patches around weathered pyrite and mafic minerals.
A broad NW trending, approximately 5 x 3 km alteration halo, is centred on the volcanic complex, with the Kisladag deposit located near the centre of this zone. A complex pattern of partially overlapping alteration types is present in the deposit area. High-grade mineralisation is typically associated with early feldspar-biotite potassic altered rocks overprinted by pervasive silica-illite, tourmaline and sericite. There are local relict zones of an early potassic assemblage of chlorite, biotite and magnetite. A late advanced argillic to intermediate argillic phase, comprising kaolinite in the main deposit, grading outward to kaolinite cut by secondary alunite, overprints the previous alteration phases.
Reserve and resource figures include (Eldorado Gold Corp website, 2008):
Proved + probable reserve - 153 Mt @ 1.12 g/t Au, included within the reources of
Measured + indicated resource - 255 Mt @ 0.95 g/t Au
Inferred resource - 141 Mt @ 0.74 g/t Au
Mainly based on report by Hatch Associates Limited (2003) available on Eldorado Gold website.
The most recent source geological information used to prepare this decription was dated: 2009.
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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Hanilci, N.,Bozkaya, G., Banks, D.A., Bozkaya, O., Prokofiev, V. and Oztas, Y., 2020 - Fluid Inclusion Characteristics of the Kisladag Porphyry Au Deposit, Western Turkey: in Minerals (MDPI) v.10, 16p. doi:10.3390/min10010064.
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Paolillo, L., Chiaradia, M. and Ulianov, A., 2022 - Zircon Petrochronology of the Kısladag Porphyry Au Deposit (Turkey) : in Econ. Geol. v.117, pp. 401-422
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Richards, J.P. and Sholeh, A., 2016 - The Tethyan Tectonic History and Cu-Au Metallogeny of Iran: in Richards, J.P. (Ed.), 2016 Tectonics and Metallogeny of the Tethyan Orogenic Belt, SEG Special Publication 19, Ch. 7, pp. 193-212.
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Yigit O, 2009 - Mineral Deposits of Turkey in Relation to Tethyan Metallogeny: Implications for Future Mineral Exploration : in Econ. Geol. v104 pp 19-51
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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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