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Skouries |
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Greece |
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Cu Au
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Super Porphyry Cu and Au
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The Skouries porphyry copper-gold deposit is part of the Kasandra Mining District of the Chalkidiki Province and is located approximately 100 km east of Thessalonika in north-eastern Greece (#Location: 23° 50' N, 40° 36'E).
The tectonic framework comprises a series of north-west trending structural units, each representing successive subduction episodes resulting from the north-east movement of the African plate between the Jurassic and Eocene. These units are separated by major thrusts or transitional zones. Successive subduction events were accompanied by volcanism and arc-type plutonic igneous intrusions. The main zones, from NE to SW are:
i). The Rhodope Massif composed of pre Variscan Precambrian and Palaeozoic mica-schists, granites and marbles, the latter of which predominate to the west. These rocks have been metamorphosed to almandine-amphibolite facies with partial anatexis.
ii). The Serbo-Macedonian Massif composed of similar rock to those of the Rhodope Massif include Proterozoic and Palaeozoic schists that are intruded by Variscan granites. This massif is the host to the deposits of the Kasandra Mining District, including Skouries.
iii). The Varda Zone, the basement of which is composed of the Jurassic ophiolite (gabbro-peridotite) and metamorphosed rhyolitic and spilitic volcanic rocks and limestones, overlain by widespread Upper Cretaceous flysch. All of these rocks have been intruded by Eocene granitic rocks. This zone is separated from the Serbo-Macedonian Massif to the east and the Pelagonian Massif to the west by deep-seated regional structures which have been the locus of Neogene calc-alkaline volcano-intrusives complexes.
iv). The Pelagonian Massif comprises basal gneiss and mica-schist overlain by a mixed series of meta-sediments, represented by gneiss, schist, quartzite, marble and dolomite, locally intruded by granitoids and pegmatites.
The Skouries deposit lies towards the eastern margin of the Serbo-Macedonian Massif, which has in turn been subdivided into two north-west trending lithostratigraphic-tectonic units, namely the a). the Vertiskos Formation composed of amphibolite gneiss flanking biotite schists with intercalated amphibolites to the west; and b). the Kerdilla Formation, made up of granitised and migmatised mica gneisses, amphibolites and marble units.
These units have been intruded by Oligocene sub-alkaline porphyry stocks which host the Skouries deposit. The deposit occurs as a sub-vertical pipe like body, associated with an elliptical pipe of coarse grained porphyritic syenite, one of a north-west trending string of syenitic plugs and dykes intruding the Vertiskos and Kerdilla Formation country rock.
The main Skouries syenite porphyry was represented at the surface by a 250 x 180 m exposure of an elliptical, composite pipe, and several E-W to NE trending dykes emplaced into the Vertiskos Formation. The Vertiskos Formation is represented by fine grained muscovite-biotite-chlorite-actinolite-feldspar-quartz schists. The Skouries porphyry comprises the following phases:
i). Early pink syenite porphyry which has undergone intense potassic alteration, accompanied by copper mineralisation associated with several veining stages, occurring as bornite, chalcopyrite and molybdenite with biotite and quartz;
ii). The Main stage porphyry which was accompanied by the high grade ore shell which contains abundant bornite and magnetite and was introduced in two pulses;
iii). Intra-mineral syenite porphyry which has only been subjected to propylitic alteration;
iv). Late oxidised porphyry accompanied by strong chlorite-pyrite-specularite alteration and remobilisation of Cu to higher levels where it was re-deposited into "S" veins of chalcopyrite-bornite ± quartz and carbonate.
The overall alteration pattern comprises a central potassic-siliceous core, surrounded by a propylitic halo. The potassic alteration comprises potassium felspar veinlets with lesser biotite veinlets in the intrusive and pervasive biotite replacement in the schists.
Mineralisation within the potassic zone is primarily chalcopyrite with lesser bornite inb 0.1 to 5 mm thick veins with disseminated chalcopyrite and bornite. Variable amounts of digenite, chalcocite, covellite, molybdenite and pyrite occur, together with rare galena and sphalerite. Magnetite is present as disseminations and in quartz veinlets. The propylitic zone contains <1% pyrite with only minor chalcopyrite. Gold occurs in its native form associated with gangue
minerals and is from a few to 160 µm in diameter. It is also found as blebs within sulphides and correlates with Cu. The ore also contains Pd.
An oxide zone is found from the surface to depths of 30 to 50 m, characterised by malachite, cuprite, chalcocite and minor azurite, covellite, digenite and native copper.
Total measured + indicated resources at Skouries as of October 2007 were: 191.2 Mt @ 0.55% Cu, 0.82 g/t Au (European Goldfields, 2007).
Tobey et al., (1998) quoted a resource of 500 Mt @ 0.47 g/t Au, 0.37% Cu,
Skouries was the subject of one of the papers delivered at an international conference in Perth in late 1998, and printed in the associated volume: Porter T M (Ed.) "Porphyry and Hydrothermal Copper and Gold Deposits: A Global Perspective", now available through PGC Publishing, Adelaide, Australia
The full abstract summarising the deposit, and the reference list from the paper can be displayed by selecting options offered below.
For detail consult this paper or other reference(s) listed below.
The most recent source geological information used to prepare this decription was dated: 1998.
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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Economou-Eliopoulos, M. and Eliopoulos, D.G., 2000 - Palladium, platinum and gold concentration in porphyry copper systems of Greece and their genetic significance: in Ore Geology Reviews v.16, pp. 59-70.
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Eliopoulos D G, Economou-Eliopoulos M 1991 - Platinum-group element and Gold contents in the Skouries Porphyry Copper deposit, Chalkidiki Peninsula, northern Greece: in Econ. Geol. v86 pp 740-749
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Eliopoulos D G, Economou-Eliopoulos M 1991 - Platinum-group element and Gold contents in the Skouries Porphyry Copper deposit, Chalkidiki Peninsula, northern Greece: in Econ. Geol. v86 pp 740-749
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Frei R 1995 - Evolution of mineralizing fluid in the Porphyry Copper system of the Skouries deposit, northeast Chalkidiki (Greece): evidence from combined Pb-Sr and stable isotope data: in Econ. Geol. v90 pp 746-762
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Kroll, T., Muller, D., Seifert, T., Herzig, P.M. and Schneider, A., 2002 - Petrology and geochemistry of the shoshonite-hosted Skouries porphyry Cu-Au deposit, Chalkidiki, Greece: in Mineralium Deposita v.37, pp. 137-144.
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Siron, C.R., Rhys, D., Thompson, J.F.H., Baker, T., Veligrakis, T., Camacho, A. and Dalampiras, L., 2018 - Structural Controls on Porphyry Au-Cu and Au-Rich Polymetallic Carbonate-Hosted Replacement Deposits of the Kassandra Mining District, Northern Greece: in Econ. Geol. v.113, pp. 309-345.
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Tobey E, Schneider A, Alegria A, Olcay L, Perantonis G, Quiroga J 1998 - Skouries porphyry copper/gold deposit, Chalkidiki, Greece: Setting, mineralisation and resources: in Porter, T.M. (Ed), 1998 Porphyry and Hydrothermal Copper and Gold Deposits - A Global Perspective PGC Publishing, Adelaide, pp 175-184
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Voudouris, P., Melfos, V., Spry, P.G., Bindi,L., Moritz, R.,Ortelli, M. and Kartal, T., 2013 - Extremely Re-Rich Molybdenite from Porphyry Cu-Mo-Au Prospects in Northeastern Greece: Mode of Occurrence, Causes of Enrichment, and Implications for Gold Exploration: in Minerals (MDPI) v.3, pp. 165-191.
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Voudouris, P., Spry, P.G., Melfos, V., Haase, K., Klemd, R., Mavrogonatos, C., Repstock, A. and Alfieris, D., 2018 - Gold deposits in Greece: Hypogene ore mineralogy as a guide for precious and critical metal exploration: in International Electronic Conference on Mineral Science, 16 to 31 July, 2018, MDPI, Switzerland, Proceedings 13p.
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| References in PGC Publishing Books: | |
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Tobey E, Schneider A, Alegria A, Olcay L, Perantonis G, Quiroga J, 1998 - Skouries porphyry copper/gold deposit, Chalkidiki, Greece: Setting, mineralisation and resources, in Porter T M, (Ed.), Porphyry and Hydrothermal Copper and Gold Deposits: A Global Perspective, pp 175-184
 Abstract
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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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