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Sapes, Sappes - Viper, Saint Demetrios, Scarp |
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Greece |
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Au Ag Cu
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
Available as Full Text for direct download or on request. |
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The Sapes (or Sappes) Gold District and Viper high-sulphidation enargite-Au-Ag-Te deposit are located ~25 km NW of Alexandroupoli in East Macedonia and Thrace, in far eastern Greece.
The Sappes Gold District includes the blind high grade Viper volcanic-hosted high-sulphidation Au-Cu-Ag deposit, the outcropping St Demetrios and adjacent Scarp epithermal Au-Te-rich mineralisation, <200 m from Viper, the similar St Barbara mineralisation, 2.5 km to south of Viper and a Cu-rich porphyry-style prospect at Koryfes Hill, (Michael, 2004; Voudouris, 2006; Voudouris et al., 2006). The porphyry and epithermal mineralisation has been dated at ~32 Ma (Ortelli et al., 2009).
Three main geotectonic units are represented in East Macedonia and Thrace: i). Palaeozoic and older metamorphic basement; ii). the Makri Unit of the Jurassic to early Creataceous age Circum Rhodope Belt; and iii). Late Eocene to Oligocene sedimentary and volcano-sedimentary rocks and Oligocene to Miocene plutonic, subvolcanic and volcanic rocks (Marchev et al., 2005; Papadopoulos, 1982; Voudouris et al., 2006).
The Viper deposit is spatially associated with a composite suite of Oligocene to Lower Miocene calc-alkaline to high-K calc-alkaline volcanic rocks, that are, in turn, linked to Middle to Upper Eocene volcaniclastic sedimentary sequences that discordantly overlying the Mesozoic Circum Rhodope metamorphic basement (Papadopoulos, 1982; Michael et al., 1995; Arikas and Voudouris, 1998; Michael, 2004; Voudouris et al., 2006; Voudouris, 2006).
The Oligocene to Lower Miocene volcanic rocks comprise a suite of andesites to dacites, and dacitic to rhyolitic porphyries (Voudouris et al., 2006), as well as hydrothermally altered polymictic and mixed monomictic to polymictic volcanic breccias. The ore is hosted by dacitic to andesitic polymictic breccia units, and locally within mixed monomictic to polymictic volcanic breccias. Within the Sappes district, equigranular to porphyritic mineralised microdiorite as at Koryfes Hill, and quartz monzodiorite dated at ~32 Ma (Voudouris, 2006) occur as small irregular stocks. Later, <27 Ma dacite and rhyolite porphyry dykes (Voudouris, 2006) intrude the monzodioritic/dioritic rocks along N to NW regional fault zones.
Mineralisation at Viper occurs as a blind, NW elongated, flat-lying, ~60 m thick orebody with estimated dimensions of 550 x 1310 m, at a depth of ~200 to 240 m below the surface. Ore occurs as hydrothermally altered, multi-stage breccias, and as disseminations in stockwork quartz-veinlets and vug-fillings. In more detail, the ore occurs as stacked lenses, diminishing in size upwards.
The deepest and largest Viper 1 lens lies at a depth of 200 to 250 m below the surface with an average thickness of 21.25 m. The overlying Viper 2 lens contains 13% of the resource and is from 170 to 190 m below the surface and averages 12.94 m in thickness. Lenses 3 to 6 are within 100 to 150 m below surface.
The hydrothermal system at Viper has evolved through several stages (from Kilias et al., 2013) from:
• pre-ore advanced argillic I + vuggy silica alteration - where the advanced argillic alteration dominates the top of the preserved hydrothermal system, and comprises an assemblage of quartz, pyrite, diaspore and pyrophyllite, grading upwards into alunite±dickite, kaolinite, fine grained pyrite and microcrystalline jigsaw quartz. The vuggy silica contains fine-grained (up to 0.5 mm) jigsaw quartz. with ~10% vugs of variable size, commonly lined by chalcedonic quartz;
• ore-stage advanced argillic II + vuggy silica alteration, occurring in two stages. Stage iia contains vuggy silica that is medium-grained, i.e., 500 µm to 3 mm, jigsaw quartz with serrated margins, accompanied by argillic alteration that is characterised by vug-filling clusters of coarse-grained minerals made up of assemblages of dickite/kaolinite-quartz-pyrite-aluminium phosphate-sulphate minerals of the alunite group. The alunite grains are tabular to bladed and overgrown by the minerals woodhouseite, svanbergite and hinsdalite. Dickite is found as fine-grained masses intergrown with very fine grained quartz and alunite. Stage iib is characterised by post-ore quartz-sericitic alteration which occurs as rosettes in vugs within colloform quartz veinlets. Fine-grained flaky clusters of sericite surround diaspore formed during the pre-ore stage advanced argillic alteration. Sericite has also been observed in sharp contact with dickite. Silicification associated with this substage is widespread, principally as colloform-banded quartz, exhibiting combined spherical, botryoidal, reniform and mammillary forms occurring along fractures, as vug fills and breccia cements. This substage indicates pH temporarily evolved to higher levels of ~6, as a result of either dilution, or the interaction of the fluid with the rock at progressively lower fluid/rock ratios and decreasing temperature;
• vein-type crosscutting advanced argillic alteration and silica indicates a return to acidic conditions. Advanced argillic alteration III is generally restricted to veins, veinlets and cavity fillings containing quartz-alunite-pyrite that crosscut all previous alteration stages. Two alunite varieties have been recognised: a). euhedral bladed and irregular coarse- to medium-grained needle-like crystals and b). pseudocubic alunite crystals. Dickite/kaolinite occurs as either dark extremely fine-grained masses or medium-grained clusters with recognisable flakes. Silicification, occurring as vug-filling amethystine quartz and barite represent the final alteration stage of the Viper hydrothermal system. Barite crystals are frequently corroded with variable sizes. Amethystine quartz has plumose or jigsaw texture and is distinguished by a gradual inward increase of the grain size towards the centre of cavities.
Ore is characterised by early barren pyrite I corroded and overprinted by: i). enargite-Au ± complex Pb-Bi-Cu sulphosalts, tellurides and selenides, coexisting with euhedral quartz, and ii). zoned pyrite II distinguished by anomalous concentrations of Au, Cu, As, Te, Bi, Pb and Se, within vuggy quartz. High-grade gold ore is also intergrown with late breccia-cementing and 'epithermal-like' vein-type banded quartz and pyrite. These observations of alteration and mineralisation are interpreted (Kilias et al., 2013) to be consistent with the changing composition, water fugacity, and density of an expanding column of metal-laden magmatic vapor, combined with changes in structural permeability. Part of the enargite-Au-quartz assemblages have probably been quenched from a sulphosalt melt at high temperatures of >575°C. The end product of the enargite-sulphhide-silica crystallisation sequence is the formation of high-grade epithermal quartz-gold colloform-banded ore during cooling and/or dilution/mixing down to ~200°C (Kilias et al., 2013).
Kilias et al., 2013 quote Glory Resources, in a 2012 ASX announcement, quote pre-mining resources, at as follows:
Viper at a 4 g/t Au cutoff,
Measured Resource - 0.71 Mt @ 22.2 g/t Au, 11.5 g/t Ag, 0.4 % Cu, and
Inferred Resource - 1.109 Mt @ 17.2 g/t Au, 8.8 g/t Ag, 0.3% Cu.
TOTAL Resource - 1.819 Mt @ 19.1 g/t Au, 9.9 g/t Ag, 0.3% Cu for 34.8 tonnes of contained gold.
Glory Resources, in a 2012 ASX announcement, quote Mineral Resources at the nearby St. Demetrios and Scarp deposits as:
St. Demetrios at a 1 g/t Au cutoff,
Measured Resource - 0.73 Mt @ 3.5 g/t Au, 3.2 g/t Ag, and
Indicated Resource - 0.05 Mt @ 2.6 g/t Au, 2.8 g/t Ag.
Scarp at a 1 g/t Au cutoff,
Measured Resource - 0.82 Mt @ 2.2 g/t Au, 1.5 g/t Ag, and
Indicated Resource - 0.05 Mt @ 1.7 g/t Au, 1.1 g/t Ag.
St. Demetrios and Scarp are both flat lying and exposed at surface to be open pittable, whilst Viper would be mined underground.
The most recent source geological information used to prepare this decription was dated: 2013.
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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Kilias, S.P., Naden, J., Paktsevanoglou, M., Giampouras, M., Stavropoulou, A., Apeiranthiti, D., Mitsis, I., Koutles, Th., Michael, K. and Christidis, C., 2013 - Multistage alteration, mineralization and ore-forming fluid properties at the Viper (Sappes) Au-Cu-Ag-Te orebody, W. Thrace, Greece: in Proceedings of the 13th International Congress, Chania, Sept. 2013 Bulletin of the Geological Society of Greece, v.48, 10p.
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